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1000 <span id="997">997</span>
1001 </pre><div class="example-wrap"><pre class="rust ">
1002 <span class="comment">// Magical Bitcoin Library</span>
1003 <span class="comment">// Written in 2020 by</span>
1004 <span class="comment">//     Alekos Filini &lt;alekos.filini@gmail.com&gt;</span>
1005 <span class="comment">//</span>
1006 <span class="comment">// Copyright (c) 2020 Magical Bitcoin</span>
1007 <span class="comment">//</span>
1008 <span class="comment">// Permission is hereby granted, free of charge, to any person obtaining a copy</span>
1009 <span class="comment">// of this software and associated documentation files (the &quot;Software&quot;), to deal</span>
1010 <span class="comment">// in the Software without restriction, including without limitation the rights</span>
1011 <span class="comment">// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell</span>
1012 <span class="comment">// copies of the Software, and to permit persons to whom the Software is</span>
1013 <span class="comment">// furnished to do so, subject to the following conditions:</span>
1014 <span class="comment">//</span>
1015 <span class="comment">// The above copyright notice and this permission notice shall be included in all</span>
1016 <span class="comment">// copies or substantial portions of the Software.</span>
1017 <span class="comment">//</span>
1018 <span class="comment">// THE SOFTWARE IS PROVIDED &quot;AS IS&quot;, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR</span>
1019 <span class="comment">// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,</span>
1020 <span class="comment">// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE</span>
1021 <span class="comment">// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER</span>
1022 <span class="comment">// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,</span>
1023 <span class="comment">// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE</span>
1024 <span class="comment">// SOFTWARE.</span>
1025
1026 <span class="doccomment">//! Coin selection</span>
1027 <span class="doccomment">//!</span>
1028 <span class="doccomment">//! This module provides the trait [`CoinSelectionAlgorithm`] that can be implemented to</span>
1029 <span class="doccomment">//! define custom coin selection algorithms.</span>
1030 <span class="doccomment">//!</span>
1031 <span class="doccomment">//! The coin selection algorithm is not globally part of a [`Wallet`](super::Wallet), instead it</span>
1032 <span class="doccomment">//! is selected whenever a [`Wallet::create_tx`](super::Wallet::create_tx) call is made, through</span>
1033 <span class="doccomment">//! the use of the [`TxBuilder`] structure, specifically with</span>
1034 <span class="doccomment">//! [`TxBuilder::coin_selection`](super::tx_builder::TxBuilder::coin_selection) method.</span>
1035 <span class="doccomment">//!</span>
1036 <span class="doccomment">//! The [`DefaultCoinSelectionAlgorithm`] selects the default coin selection algorithm that</span>
1037 <span class="doccomment">//! [`TxBuilder`] uses, if it&#39;s not explicitly overridden.</span>
1038 <span class="doccomment">//!</span>
1039 <span class="doccomment">//! [`TxBuilder`]: super::tx_builder::TxBuilder</span>
1040 <span class="doccomment">//!</span>
1041 <span class="doccomment">//! ## Example</span>
1042 <span class="doccomment">//!</span>
1043 <span class="doccomment">//! ```no_run</span>
1044 <span class="doccomment">//! # use std::str::FromStr;</span>
1045 <span class="doccomment">//! # use bitcoin::*;</span>
1046 <span class="doccomment">//! # use bdk::wallet::coin_selection::*;</span>
1047 <span class="doccomment">//! # use bdk::database::Database;</span>
1048 <span class="doccomment">//! # use bdk::*;</span>
1049 <span class="doccomment">//! # const TXIN_BASE_WEIGHT: usize = (32 + 4 + 4 + 1) * 4;</span>
1050 <span class="doccomment">//! #[derive(Debug)]</span>
1051 <span class="doccomment">//! struct AlwaysSpendEverything;</span>
1052 <span class="doccomment">//!</span>
1053 <span class="doccomment">//! impl&lt;D: Database&gt; CoinSelectionAlgorithm&lt;D&gt; for AlwaysSpendEverything {</span>
1054 <span class="doccomment">//!     fn coin_select(</span>
1055 <span class="doccomment">//!         &amp;self,</span>
1056 <span class="doccomment">//!         database: &amp;D,</span>
1057 <span class="doccomment">//!         required_utxos: Vec&lt;(UTXO, usize)&gt;,</span>
1058 <span class="doccomment">//!         optional_utxos: Vec&lt;(UTXO, usize)&gt;,</span>
1059 <span class="doccomment">//!         fee_rate: FeeRate,</span>
1060 <span class="doccomment">//!         amount_needed: u64,</span>
1061 <span class="doccomment">//!         fee_amount: f32,</span>
1062 <span class="doccomment">//!     ) -&gt; Result&lt;CoinSelectionResult, bdk::Error&gt; {</span>
1063 <span class="doccomment">//!         let mut selected_amount = 0;</span>
1064 <span class="doccomment">//!         let mut additional_weight = 0;</span>
1065 <span class="doccomment">//!         let all_utxos_selected = required_utxos</span>
1066 <span class="doccomment">//!             .into_iter().chain(optional_utxos)</span>
1067 <span class="doccomment">//!             .scan((&amp;mut selected_amount, &amp;mut additional_weight), |(selected_amount, additional_weight), (utxo, weight)| {</span>
1068 <span class="doccomment">//!                 **selected_amount += utxo.txout.value;</span>
1069 <span class="doccomment">//!                 **additional_weight += TXIN_BASE_WEIGHT + weight;</span>
1070 <span class="doccomment">//!</span>
1071 <span class="doccomment">//!                 Some(utxo)</span>
1072 <span class="doccomment">//!             })</span>
1073 <span class="doccomment">//!             .collect::&lt;Vec&lt;_&gt;&gt;();</span>
1074 <span class="doccomment">//!         let additional_fees = additional_weight as f32 * fee_rate.as_sat_vb() / 4.0;</span>
1075 <span class="doccomment">//!</span>
1076 <span class="doccomment">//!         if (fee_amount + additional_fees).ceil() as u64 + amount_needed &gt; selected_amount {</span>
1077 <span class="doccomment">//!             return Err(bdk::Error::InsufficientFunds);</span>
1078 <span class="doccomment">//!         }</span>
1079 <span class="doccomment">//!</span>
1080 <span class="doccomment">//!         Ok(CoinSelectionResult {</span>
1081 <span class="doccomment">//!             selected: all_utxos_selected,</span>
1082 <span class="doccomment">//!             selected_amount,</span>
1083 <span class="doccomment">//!             fee_amount: fee_amount + additional_fees,</span>
1084 <span class="doccomment">//!         })</span>
1085 <span class="doccomment">//!     }</span>
1086 <span class="doccomment">//! }</span>
1087 <span class="doccomment">//!</span>
1088 <span class="doccomment">//! # let wallet: OfflineWallet&lt;_&gt; = Wallet::new_offline(&quot;&quot;, None, Network::Testnet, bdk::database::MemoryDatabase::default())?;</span>
1089 <span class="doccomment">//! // create wallet, sync, ...</span>
1090 <span class="doccomment">//!</span>
1091 <span class="doccomment">//! let to_address = Address::from_str(&quot;2N4eQYCbKUHCCTUjBJeHcJp9ok6J2GZsTDt&quot;).unwrap();</span>
1092 <span class="doccomment">//! let (psbt, details) = wallet.create_tx(</span>
1093 <span class="doccomment">//!     TxBuilder::with_recipients(vec![(to_address.script_pubkey(), 50_000)])</span>
1094 <span class="doccomment">//!         .coin_selection(AlwaysSpendEverything),</span>
1095 <span class="doccomment">//! )?;</span>
1096 <span class="doccomment">//!</span>
1097 <span class="doccomment">//! // inspect, sign, broadcast, ...</span>
1098 <span class="doccomment">//!</span>
1099 <span class="doccomment">//! # Ok::&lt;(), bdk::Error&gt;(())</span>
1100 <span class="doccomment">//! ```</span>
1101
1102 <span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">database</span>::<span class="ident">Database</span>;
1103 <span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">error</span>::<span class="ident">Error</span>;
1104 <span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">types</span>::{<span class="ident">FeeRate</span>, <span class="ident">UTXO</span>};
1105
1106 <span class="kw">use</span> <span class="ident">rand</span>::<span class="ident">seq</span>::<span class="ident">SliceRandom</span>;
1107 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span>
1108 <span class="kw">use</span> <span class="ident">rand</span>::<span class="ident">thread_rng</span>;
1109 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
1110 <span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">rngs</span>::<span class="ident">StdRng</span>, <span class="ident">SeedableRng</span>};
1111
1112 <span class="doccomment">/// Default coin selection algorithm used by [`TxBuilder`](super::tx_builder::TxBuilder) if not</span>
1113 <span class="doccomment">/// overridden</span>
1114 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span>
1115 <span class="kw">pub</span> <span class="kw">type</span> <span class="ident">DefaultCoinSelectionAlgorithm</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>;
1116 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
1117 <span class="kw">pub</span> <span class="kw">type</span> <span class="ident">DefaultCoinSelectionAlgorithm</span> <span class="op">=</span> <span class="ident">LargestFirstCoinSelection</span>; <span class="comment">// make the tests more predictable</span>
1118
1119 <span class="comment">// Base weight of a Txin, not counting the weight needed for satisfying it.</span>
1120 <span class="comment">// prev_txid (32 bytes) + prev_vout (4 bytes) + sequence (4 bytes) + script_len (1 bytes)</span>
1121 <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const</span> <span class="ident">TXIN_BASE_WEIGHT</span>: <span class="ident">usize</span> <span class="op">=</span> (<span class="number">32</span> <span class="op">+</span> <span class="number">4</span> <span class="op">+</span> <span class="number">4</span> <span class="op">+</span> <span class="number">1</span>) <span class="op">*</span> <span class="number">4</span>;
1122
1123 <span class="doccomment">/// Result of a successful coin selection</span>
1124 <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
1125 <span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">CoinSelectionResult</span> {
1126     <span class="doccomment">/// List of outputs selected for use as inputs</span>
1127     <span class="kw">pub</span> <span class="ident">selected</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">UTXO</span><span class="op">&gt;</span>,
1128     <span class="doccomment">/// Sum of the selected inputs&#39; value</span>
1129     <span class="kw">pub</span> <span class="ident">selected_amount</span>: <span class="ident">u64</span>,
1130     <span class="doccomment">/// Total fee amount in satoshi</span>
1131     <span class="kw">pub</span> <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1132 }
1133
1134 <span class="doccomment">/// Trait for generalized coin selection algorithms</span>
1135 <span class="doccomment">///</span>
1136 <span class="doccomment">/// This trait can be implemented to make the [`Wallet`](super::Wallet) use a customized coin</span>
1137 <span class="doccomment">/// selection algorithm when it creates transactions.</span>
1138 <span class="doccomment">///</span>
1139 <span class="doccomment">/// For an example see [this module](crate::wallet::coin_selection)&#39;s documentation.</span>
1140 <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">CoinSelectionAlgorithm</span><span class="op">&lt;</span><span class="ident">D</span>: <span class="ident">Database</span><span class="op">&gt;</span>: <span class="ident">std</span>::<span class="ident">fmt</span>::<span class="ident">Debug</span> {
1141     <span class="doccomment">/// Perform the coin selection</span>
1142     <span class="doccomment">///</span>
1143     <span class="doccomment">/// - `database`: a reference to the wallet&#39;s database that can be used to lookup additional</span>
1144     <span class="doccomment">///               details for a specific UTXO</span>
1145     <span class="doccomment">/// - `required_utxos`: the utxos that must be spent regardless of `amount_needed` with their</span>
1146     <span class="doccomment">///                     weight cost</span>
1147     <span class="doccomment">/// - `optional_utxos`: the remaining available utxos to satisfy `amount_needed` with their</span>
1148     <span class="doccomment">///                     weight cost</span>
1149     <span class="doccomment">/// - `fee_rate`: fee rate to use</span>
1150     <span class="doccomment">/// - `amount_needed`: the amount in satoshi to select</span>
1151     <span class="doccomment">/// - `fee_amount`: the amount of fees in satoshi already accumulated from adding outputs and</span>
1152     <span class="doccomment">///                 the transaction&#39;s header</span>
1153     <span class="kw">fn</span> <span class="ident">coin_select</span>(
1154         <span class="kw-2">&amp;</span><span class="self">self</span>,
1155         <span class="ident">database</span>: <span class="kw-2">&amp;</span><span class="ident">D</span>,
1156         <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>,
1157         <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>,
1158         <span class="ident">fee_rate</span>: <span class="ident">FeeRate</span>,
1159         <span class="ident">amount_needed</span>: <span class="ident">u64</span>,
1160         <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1161     ) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">CoinSelectionResult</span>, <span class="ident">Error</span><span class="op">&gt;</span>;
1162 }
1163
1164 <span class="doccomment">/// Simple and dumb coin selection</span>
1165 <span class="doccomment">///</span>
1166 <span class="doccomment">/// This coin selection algorithm sorts the available UTXOs by value and then picks them starting</span>
1167 <span class="doccomment">/// from the largest ones until the required amount is reached.</span>
1168 <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Default</span>)]</span>
1169 <span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">LargestFirstCoinSelection</span>;
1170
1171 <span class="kw">impl</span><span class="op">&lt;</span><span class="ident">D</span>: <span class="ident">Database</span><span class="op">&gt;</span> <span class="ident">CoinSelectionAlgorithm</span><span class="op">&lt;</span><span class="ident">D</span><span class="op">&gt;</span> <span class="kw">for</span> <span class="ident">LargestFirstCoinSelection</span> {
1172     <span class="kw">fn</span> <span class="ident">coin_select</span>(
1173         <span class="kw-2">&amp;</span><span class="self">self</span>,
1174         <span class="ident">_database</span>: <span class="kw-2">&amp;</span><span class="ident">D</span>,
1175         <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>,
1176         <span class="kw-2">mut</span> <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>,
1177         <span class="ident">fee_rate</span>: <span class="ident">FeeRate</span>,
1178         <span class="ident">amount_needed</span>: <span class="ident">u64</span>,
1179         <span class="kw-2">mut</span> <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1180     ) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">CoinSelectionResult</span>, <span class="ident">Error</span><span class="op">&gt;</span> {
1181         <span class="kw">let</span> <span class="ident">calc_fee_bytes</span> <span class="op">=</span> <span class="op">|</span><span class="ident">wu</span><span class="op">|</span> (<span class="ident">wu</span> <span class="kw">as</span> <span class="ident">f32</span>) <span class="op">*</span> <span class="ident">fee_rate</span>.<span class="ident">as_sat_vb</span>() <span class="op">/</span> <span class="number">4.0</span>;
1182
1183         <span class="ident">log</span>::<span class="macro">debug</span><span class="macro">!</span>(
1184             <span class="string">&quot;amount_needed = `{}`, fee_amount = `{}`, fee_rate = `{:?}`&quot;</span>,
1185             <span class="ident">amount_needed</span>,
1186             <span class="ident">fee_amount</span>,
1187             <span class="ident">fee_rate</span>
1188         );
1189
1190         <span class="comment">// We put the &quot;required UTXOs&quot; first and make sure the optional UTXOs are sorted,</span>
1191         <span class="comment">// initially smallest to largest, before being reversed with `.rev()`.</span>
1192         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> {
1193             <span class="ident">optional_utxos</span>.<span class="ident">sort_unstable_by_key</span>(<span class="op">|</span>(<span class="ident">utxo</span>, <span class="kw">_</span>)<span class="op">|</span> <span class="ident">utxo</span>.<span class="ident">txout</span>.<span class="ident">value</span>);
1194             <span class="ident">required_utxos</span>
1195                 .<span class="ident">into_iter</span>()
1196                 .<span class="ident">map</span>(<span class="op">|</span><span class="ident">utxo</span><span class="op">|</span> (<span class="bool-val">true</span>, <span class="ident">utxo</span>))
1197                 .<span class="ident">chain</span>(<span class="ident">optional_utxos</span>.<span class="ident">into_iter</span>().<span class="ident">rev</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">utxo</span><span class="op">|</span> (<span class="bool-val">false</span>, <span class="ident">utxo</span>)))
1198         };
1199
1200         <span class="comment">// Keep including inputs until we&#39;ve got enough.</span>
1201         <span class="comment">// Store the total input value in selected_amount and the total fee being paid in fee_amount</span>
1202         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">selected_amount</span> <span class="op">=</span> <span class="number">0</span>;
1203         <span class="kw">let</span> <span class="ident">selected</span> <span class="op">=</span> <span class="ident">utxos</span>
1204             .<span class="ident">scan</span>(
1205                 (<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">selected_amount</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fee_amount</span>),
1206                 <span class="op">|</span>(<span class="ident">selected_amount</span>, <span class="ident">fee_amount</span>), (<span class="ident">must_use</span>, (<span class="ident">utxo</span>, <span class="ident">weight</span>))<span class="op">|</span> {
1207                     <span class="kw">if</span> <span class="ident">must_use</span> <span class="op">|</span><span class="op">|</span> <span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">selected_amount</span> <span class="op">&lt;</span> <span class="ident">amount_needed</span> <span class="op">+</span> (<span class="ident">fee_amount</span>.<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">u64</span>) {
1208                         <span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">fee_amount</span> <span class="op">+</span><span class="op">=</span> <span class="ident">calc_fee_bytes</span>(<span class="ident">TXIN_BASE_WEIGHT</span> <span class="op">+</span> <span class="ident">weight</span>);
1209                         <span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">selected_amount</span> <span class="op">+</span><span class="op">=</span> <span class="ident">utxo</span>.<span class="ident">txout</span>.<span class="ident">value</span>;
1210
1211                         <span class="ident">log</span>::<span class="macro">debug</span><span class="macro">!</span>(
1212                             <span class="string">&quot;Selected {}, updated fee_amount = `{}`&quot;</span>,
1213                             <span class="ident">utxo</span>.<span class="ident">outpoint</span>,
1214                             <span class="ident">fee_amount</span>
1215                         );
1216
1217                         <span class="prelude-val">Some</span>(<span class="ident">utxo</span>)
1218                     } <span class="kw">else</span> {
1219                         <span class="prelude-val">None</span>
1220                     }
1221                 },
1222             )
1223             .<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>();
1224
1225         <span class="kw">if</span> <span class="ident">selected_amount</span> <span class="op">&lt;</span> <span class="ident">amount_needed</span> <span class="op">+</span> (<span class="ident">fee_amount</span>.<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">u64</span>) {
1226             <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Error</span>::<span class="ident">InsufficientFunds</span>);
1227         }
1228
1229         <span class="prelude-val">Ok</span>(<span class="ident">CoinSelectionResult</span> {
1230             <span class="ident">selected</span>,
1231             <span class="ident">fee_amount</span>,
1232             <span class="ident">selected_amount</span>,
1233         })
1234     }
1235 }
1236
1237 <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Clone</span>)]</span>
1238 <span class="comment">// Adds fee information to an UTXO.</span>
1239 <span class="kw">struct</span> <span class="ident">OutputGroup</span> {
1240     <span class="ident">utxo</span>: <span class="ident">UTXO</span>,
1241     <span class="comment">// weight needed to satisfy the UTXO, as described in `Descriptor::max_satisfaction_weight`</span>
1242     <span class="ident">satisfaction_weight</span>: <span class="ident">usize</span>,
1243     <span class="comment">// Amount of fees for spending a certain utxo, calculated using a certain FeeRate</span>
1244     <span class="ident">fee</span>: <span class="ident">f32</span>,
1245     <span class="comment">// The effective value of the UTXO, i.e., the utxo value minus the fee for spending it</span>
1246     <span class="ident">effective_value</span>: <span class="ident">i64</span>,
1247 }
1248
1249 <span class="kw">impl</span> <span class="ident">OutputGroup</span> {
1250     <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">utxo</span>: <span class="ident">UTXO</span>, <span class="ident">satisfaction_weight</span>: <span class="ident">usize</span>, <span class="ident">fee_rate</span>: <span class="ident">FeeRate</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="self">Self</span> {
1251         <span class="kw">let</span> <span class="ident">fee</span> <span class="op">=</span> (<span class="ident">TXIN_BASE_WEIGHT</span> <span class="op">+</span> <span class="ident">satisfaction_weight</span>) <span class="kw">as</span> <span class="ident">f32</span> <span class="op">/</span> <span class="number">4.0</span> <span class="op">*</span> <span class="ident">fee_rate</span>.<span class="ident">as_sat_vb</span>();
1252         <span class="kw">let</span> <span class="ident">effective_value</span> <span class="op">=</span> <span class="ident">utxo</span>.<span class="ident">txout</span>.<span class="ident">value</span> <span class="kw">as</span> <span class="ident">i64</span> <span class="op">-</span> <span class="ident">fee</span>.<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">i64</span>;
1253         <span class="ident">OutputGroup</span> {
1254             <span class="ident">utxo</span>,
1255             <span class="ident">satisfaction_weight</span>,
1256             <span class="ident">effective_value</span>,
1257             <span class="ident">fee</span>,
1258         }
1259     }
1260 }
1261
1262 <span class="doccomment">/// Branch and bound coin selection</span>
1263 <span class="doccomment">///</span>
1264 <span class="doccomment">/// Code adapted from Bitcoin Core&#39;s implementation and from Mark Erhardt Master&#39;s Thesis: &lt;http://murch.one/wp-content/uploads/2016/11/erhardt2016coinselection.pdf&gt;</span>
1265 <span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
1266 <span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">BranchAndBoundCoinSelection</span> {
1267     <span class="ident">size_of_change</span>: <span class="ident">u64</span>,
1268 }
1269
1270 <span class="kw">impl</span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">BranchAndBoundCoinSelection</span> {
1271     <span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-</span><span class="op">&gt;</span> <span class="self">Self</span> {
1272         <span class="self">Self</span> {
1273             <span class="comment">// P2WPKH cost of change -&gt; value (8 bytes) + script len (1 bytes) + script (22 bytes)</span>
1274             <span class="ident">size_of_change</span>: <span class="number">8</span> <span class="op">+</span> <span class="number">1</span> <span class="op">+</span> <span class="number">22</span>,
1275         }
1276     }
1277 }
1278
1279 <span class="kw">impl</span> <span class="ident">BranchAndBoundCoinSelection</span> {
1280     <span class="doccomment">/// Create new instance with target size for change output</span>
1281     <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">size_of_change</span>: <span class="ident">u64</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="self">Self</span> {
1282         <span class="self">Self</span> { <span class="ident">size_of_change</span> }
1283     }
1284 }
1285
1286 <span class="kw">const</span> <span class="ident">BNB_TOTAL_TRIES</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">100_000</span>;
1287
1288 <span class="kw">impl</span><span class="op">&lt;</span><span class="ident">D</span>: <span class="ident">Database</span><span class="op">&gt;</span> <span class="ident">CoinSelectionAlgorithm</span><span class="op">&lt;</span><span class="ident">D</span><span class="op">&gt;</span> <span class="kw">for</span> <span class="ident">BranchAndBoundCoinSelection</span> {
1289     <span class="kw">fn</span> <span class="ident">coin_select</span>(
1290         <span class="kw-2">&amp;</span><span class="self">self</span>,
1291         <span class="ident">_database</span>: <span class="kw-2">&amp;</span><span class="ident">D</span>,
1292         <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>,
1293         <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>,
1294         <span class="ident">fee_rate</span>: <span class="ident">FeeRate</span>,
1295         <span class="ident">amount_needed</span>: <span class="ident">u64</span>,
1296         <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1297     ) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">CoinSelectionResult</span>, <span class="ident">Error</span><span class="op">&gt;</span> {
1298         <span class="comment">// Mapping every (UTXO, usize) to an output group</span>
1299         <span class="kw">let</span> <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">required_utxos</span>
1300             .<span class="ident">into_iter</span>()
1301             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1302             .<span class="ident">collect</span>();
1303
1304         <span class="comment">// Mapping every (UTXO, usize) to an output group.</span>
1305         <span class="comment">// Filtering UTXOs with an effective_value &lt; 0, as the fee paid for</span>
1306         <span class="comment">// adding them is more than their value</span>
1307         <span class="kw">let</span> <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">optional_utxos</span>
1308             .<span class="ident">into_iter</span>()
1309             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1310             .<span class="ident">filter</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">u</span>.<span class="ident">effective_value</span> <span class="op">&gt;</span> <span class="number">0</span>)
1311             .<span class="ident">collect</span>();
1312
1313         <span class="kw">let</span> <span class="ident">curr_value</span> <span class="op">=</span> <span class="ident">required_utxos</span>
1314             .<span class="ident">iter</span>()
1315             .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>);
1316
1317         <span class="kw">let</span> <span class="ident">curr_available_value</span> <span class="op">=</span> <span class="ident">optional_utxos</span>
1318             .<span class="ident">iter</span>()
1319             .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>);
1320
1321         <span class="kw">let</span> <span class="ident">actual_target</span> <span class="op">=</span> <span class="ident">fee_amount</span>.<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">u64</span> <span class="op">+</span> <span class="ident">amount_needed</span>;
1322         <span class="kw">let</span> <span class="ident">cost_of_change</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">size_of_change</span> <span class="kw">as</span> <span class="ident">f32</span> <span class="op">*</span> <span class="ident">fee_rate</span>.<span class="ident">as_sat_vb</span>();
1323
1324         <span class="kw">if</span> <span class="ident">curr_available_value</span> <span class="op">+</span> <span class="ident">curr_value</span> <span class="op">&lt;</span> <span class="ident">actual_target</span> {
1325             <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Error</span>::<span class="ident">InsufficientFunds</span>);
1326         }
1327
1328         <span class="prelude-val">Ok</span>(<span class="self">self</span>
1329             .<span class="ident">bnb</span>(
1330                 <span class="ident">required_utxos</span>.<span class="ident">clone</span>(),
1331                 <span class="ident">optional_utxos</span>.<span class="ident">clone</span>(),
1332                 <span class="ident">curr_value</span>,
1333                 <span class="ident">curr_available_value</span>,
1334                 <span class="ident">actual_target</span>,
1335                 <span class="ident">fee_amount</span>,
1336                 <span class="ident">cost_of_change</span>,
1337             )
1338             .<span class="ident">unwrap_or_else</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> {
1339                 <span class="self">self</span>.<span class="ident">single_random_draw</span>(
1340                     <span class="ident">required_utxos</span>,
1341                     <span class="ident">optional_utxos</span>,
1342                     <span class="ident">curr_value</span>,
1343                     <span class="ident">actual_target</span>,
1344                     <span class="ident">fee_amount</span>,
1345                 )
1346             }))
1347     }
1348 }
1349
1350 <span class="kw">impl</span> <span class="ident">BranchAndBoundCoinSelection</span> {
1351     <span class="comment">// TODO: make this more Rust-onic :)</span>
1352     <span class="comment">// (And perhpaps refactor with less arguments?)</span>
1353     <span class="attribute">#[<span class="ident">allow</span>(<span class="ident">clippy</span>::<span class="ident">too_many_arguments</span>)]</span>
1354     <span class="kw">fn</span> <span class="ident">bnb</span>(
1355         <span class="kw-2">&amp;</span><span class="self">self</span>,
1356         <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span>,
1357         <span class="kw-2">mut</span> <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span>,
1358         <span class="kw-2">mut</span> <span class="ident">curr_value</span>: <span class="ident">u64</span>,
1359         <span class="kw-2">mut</span> <span class="ident">curr_available_value</span>: <span class="ident">u64</span>,
1360         <span class="ident">actual_target</span>: <span class="ident">u64</span>,
1361         <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1362         <span class="ident">cost_of_change</span>: <span class="ident">f32</span>,
1363     ) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">CoinSelectionResult</span>, <span class="ident">Error</span><span class="op">&gt;</span> {
1364         <span class="comment">// current_selection[i] will contain true if we are using optional_utxos[i],</span>
1365         <span class="comment">// false otherwise. Note that current_selection.len() could be less than</span>
1366         <span class="comment">// optional_utxos.len(), it just means that we still haven&#39;t decided if we should keep</span>
1367         <span class="comment">// certain optional_utxos or not.</span>
1368         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">current_selection</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">bool</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">with_capacity</span>(<span class="ident">optional_utxos</span>.<span class="ident">len</span>());
1369
1370         <span class="comment">// Sort the utxo_pool</span>
1371         <span class="ident">optional_utxos</span>.<span class="ident">sort_unstable_by_key</span>(<span class="op">|</span><span class="ident">a</span><span class="op">|</span> <span class="ident">a</span>.<span class="ident">effective_value</span>);
1372         <span class="ident">optional_utxos</span>.<span class="ident">reverse</span>();
1373
1374         <span class="comment">// Contains the best selection we found</span>
1375         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">best_selection</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">new</span>();
1376         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">best_selection_value</span> <span class="op">=</span> <span class="prelude-val">None</span>;
1377
1378         <span class="comment">// Depth First search loop for choosing the UTXOs</span>
1379         <span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">BNB_TOTAL_TRIES</span> {
1380             <span class="comment">// Conditions for starting a backtrack</span>
1381             <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">backtrack</span> <span class="op">=</span> <span class="bool-val">false</span>;
1382             <span class="comment">// Cannot possibly reach target with the amount remaining in the curr_available_value,</span>
1383             <span class="comment">// or the selected value is out of range.</span>
1384             <span class="comment">// Go back and try other branch</span>
1385             <span class="kw">if</span> <span class="ident">curr_value</span> <span class="op">+</span> <span class="ident">curr_available_value</span> <span class="op">&lt;</span> <span class="ident">actual_target</span>
1386                 <span class="op">|</span><span class="op">|</span> <span class="ident">curr_value</span> <span class="op">&gt;</span> <span class="ident">actual_target</span> <span class="op">+</span> <span class="ident">cost_of_change</span> <span class="kw">as</span> <span class="ident">u64</span>
1387             {
1388                 <span class="ident">backtrack</span> <span class="op">=</span> <span class="bool-val">true</span>;
1389             } <span class="kw">else</span> <span class="kw">if</span> <span class="ident">curr_value</span> <span class="op">&gt;</span><span class="op">=</span> <span class="ident">actual_target</span> {
1390                 <span class="comment">// Selected value is within range, there&#39;s no point in going forward. Start</span>
1391                 <span class="comment">// backtracking</span>
1392                 <span class="ident">backtrack</span> <span class="op">=</span> <span class="bool-val">true</span>;
1393
1394                 <span class="comment">// If we found a solution better than the previous one, or if there wasn&#39;t previous</span>
1395                 <span class="comment">// solution, update the best solution</span>
1396                 <span class="kw">if</span> <span class="ident">best_selection_value</span>.<span class="ident">is_none</span>() <span class="op">|</span><span class="op">|</span> <span class="ident">curr_value</span> <span class="op">&lt;</span> <span class="ident">best_selection_value</span>.<span class="ident">unwrap</span>() {
1397                     <span class="ident">best_selection</span> <span class="op">=</span> <span class="ident">current_selection</span>.<span class="ident">clone</span>();
1398                     <span class="ident">best_selection_value</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">curr_value</span>);
1399                 }
1400
1401                 <span class="comment">// If we found a perfect match, break here</span>
1402                 <span class="kw">if</span> <span class="ident">curr_value</span> <span class="op">=</span><span class="op">=</span> <span class="ident">actual_target</span> {
1403                     <span class="kw">break</span>;
1404                 }
1405             }
1406
1407             <span class="comment">// Backtracking, moving backwards</span>
1408             <span class="kw">if</span> <span class="ident">backtrack</span> {
1409                 <span class="comment">// Walk backwards to find the last included UTXO that still needs to have its omission branch traversed.</span>
1410                 <span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="bool-val">false</span>) <span class="op">=</span> <span class="ident">current_selection</span>.<span class="ident">last</span>() {
1411                     <span class="ident">current_selection</span>.<span class="ident">pop</span>();
1412                     <span class="ident">curr_available_value</span> <span class="op">+</span><span class="op">=</span>
1413                         <span class="ident">optional_utxos</span>[<span class="ident">current_selection</span>.<span class="ident">len</span>()].<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>;
1414                 }
1415
1416                 <span class="kw">if</span> <span class="ident">current_selection</span>.<span class="ident">last_mut</span>().<span class="ident">is_none</span>() {
1417                     <span class="comment">// We have walked back to the first utxo and no branch is untraversed. All solutions searched</span>
1418                     <span class="comment">// If best selection is empty, then there&#39;s no exact match</span>
1419                     <span class="kw">if</span> <span class="ident">best_selection</span>.<span class="ident">is_empty</span>() {
1420                         <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Error</span>::<span class="ident">BnBNoExactMatch</span>);
1421                     }
1422                     <span class="kw">break</span>;
1423                 }
1424
1425                 <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">c</span>) <span class="op">=</span> <span class="ident">current_selection</span>.<span class="ident">last_mut</span>() {
1426                     <span class="comment">// Output was included on previous iterations, try excluding now.</span>
1427                     <span class="kw-2">*</span><span class="ident">c</span> <span class="op">=</span> <span class="bool-val">false</span>;
1428                 }
1429
1430                 <span class="kw">let</span> <span class="ident">utxo</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="ident">optional_utxos</span>[<span class="ident">current_selection</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span>];
1431                 <span class="ident">curr_value</span> <span class="op">-</span><span class="op">=</span> <span class="ident">utxo</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>;
1432             } <span class="kw">else</span> {
1433                 <span class="comment">// Moving forwards, continuing down this branch</span>
1434                 <span class="kw">let</span> <span class="ident">utxo</span> <span class="op">=</span> <span class="kw-2">&amp;</span><span class="ident">optional_utxos</span>[<span class="ident">current_selection</span>.<span class="ident">len</span>()];
1435
1436                 <span class="comment">// Remove this utxo from the curr_available_value utxo amount</span>
1437                 <span class="ident">curr_available_value</span> <span class="op">-</span><span class="op">=</span> <span class="ident">utxo</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>;
1438
1439                 <span class="comment">// Inclusion branch first (Largest First Exploration)</span>
1440                 <span class="ident">current_selection</span>.<span class="ident">push</span>(<span class="bool-val">true</span>);
1441                 <span class="ident">curr_value</span> <span class="op">+</span><span class="op">=</span> <span class="ident">utxo</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>;
1442             }
1443         }
1444
1445         <span class="comment">// Check for solution</span>
1446         <span class="kw">if</span> <span class="ident">best_selection</span>.<span class="ident">is_empty</span>() {
1447             <span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">Error</span>::<span class="ident">BnBTotalTriesExceeded</span>);
1448         }
1449
1450         <span class="comment">// Set output set</span>
1451         <span class="kw">let</span> <span class="ident">selected_utxos</span> <span class="op">=</span> <span class="ident">optional_utxos</span>
1452             .<span class="ident">into_iter</span>()
1453             .<span class="ident">zip</span>(<span class="ident">best_selection</span>)
1454             .<span class="ident">filter_map</span>(<span class="op">|</span>(<span class="ident">optional</span>, <span class="ident">is_in_best</span>)<span class="op">|</span> <span class="kw">if</span> <span class="ident">is_in_best</span> { <span class="prelude-val">Some</span>(<span class="ident">optional</span>) } <span class="kw">else</span> { <span class="prelude-val">None</span> })
1455             .<span class="ident">collect</span>();
1456
1457         <span class="prelude-val">Ok</span>(<span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">calculate_cs_result</span>(
1458             <span class="ident">selected_utxos</span>,
1459             <span class="ident">required_utxos</span>,
1460             <span class="ident">fee_amount</span>,
1461         ))
1462     }
1463
1464     <span class="kw">fn</span> <span class="ident">single_random_draw</span>(
1465         <span class="kw-2">&amp;</span><span class="self">self</span>,
1466         <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span>,
1467         <span class="kw-2">mut</span> <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span>,
1468         <span class="ident">curr_value</span>: <span class="ident">u64</span>,
1469         <span class="ident">actual_target</span>: <span class="ident">u64</span>,
1470         <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1471     ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">CoinSelectionResult</span> {
1472         <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">test</span>))]</span>
1473         <span class="ident">optional_utxos</span>.<span class="ident">shuffle</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">thread_rng</span>());
1474         <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
1475         {
1476             <span class="kw">let</span> <span class="ident">seed</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">32</span>];
1477             <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span>: <span class="ident">StdRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>(<span class="ident">seed</span>);
1478             <span class="ident">optional_utxos</span>.<span class="ident">shuffle</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>);
1479         }
1480
1481         <span class="kw">let</span> <span class="ident">selected_utxos</span> <span class="op">=</span> <span class="ident">optional_utxos</span>
1482             .<span class="ident">into_iter</span>()
1483             .<span class="ident">scan</span>(<span class="ident">curr_value</span>, <span class="op">|</span><span class="ident">curr_value</span>, <span class="ident">utxo</span><span class="op">|</span> {
1484                 <span class="kw">if</span> <span class="kw-2">*</span><span class="ident">curr_value</span> <span class="op">&gt;</span><span class="op">=</span> <span class="ident">actual_target</span> {
1485                     <span class="prelude-val">None</span>
1486                 } <span class="kw">else</span> {
1487                     <span class="kw-2">*</span><span class="ident">curr_value</span> <span class="op">+</span><span class="op">=</span> <span class="ident">utxo</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>;
1488                     <span class="prelude-val">Some</span>(<span class="ident">utxo</span>)
1489                 }
1490             })
1491             .<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>();
1492
1493         <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">calculate_cs_result</span>(<span class="ident">selected_utxos</span>, <span class="ident">required_utxos</span>, <span class="ident">fee_amount</span>)
1494     }
1495
1496     <span class="kw">fn</span> <span class="ident">calculate_cs_result</span>(
1497         <span class="kw-2">mut</span> <span class="ident">selected_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span>,
1498         <span class="kw-2">mut</span> <span class="ident">required_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span>,
1499         <span class="kw-2">mut</span> <span class="ident">fee_amount</span>: <span class="ident">f32</span>,
1500     ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">CoinSelectionResult</span> {
1501         <span class="ident">selected_utxos</span>.<span class="ident">append</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">required_utxos</span>);
1502         <span class="ident">fee_amount</span> <span class="op">+</span><span class="op">=</span> <span class="ident">selected_utxos</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">u</span>.<span class="ident">fee</span>).<span class="ident">sum</span>::<span class="op">&lt;</span><span class="ident">f32</span><span class="op">&gt;</span>();
1503         <span class="kw">let</span> <span class="ident">selected</span> <span class="op">=</span> <span class="ident">selected_utxos</span>
1504             .<span class="ident">into_iter</span>()
1505             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">u</span>.<span class="ident">utxo</span>)
1506             .<span class="ident">collect</span>::<span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span><span class="op">&gt;</span>();
1507         <span class="kw">let</span> <span class="ident">selected_amount</span> <span class="op">=</span> <span class="ident">selected</span>.<span class="ident">iter</span>().<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">u</span>.<span class="ident">txout</span>.<span class="ident">value</span>).<span class="ident">sum</span>();
1508
1509         <span class="ident">CoinSelectionResult</span> {
1510             <span class="ident">selected</span>,
1511             <span class="ident">fee_amount</span>,
1512             <span class="ident">selected_amount</span>,
1513         }
1514     }
1515 }
1516
1517 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
1518 <span class="kw">mod</span> <span class="ident">test</span> {
1519     <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">str</span>::<span class="ident">FromStr</span>;
1520
1521     <span class="kw">use</span> <span class="ident">bitcoin</span>::{<span class="ident">OutPoint</span>, <span class="ident">Script</span>, <span class="ident">TxOut</span>};
1522
1523     <span class="kw">use</span> <span class="kw">super</span>::<span class="kw-2">*</span>;
1524     <span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">database</span>::<span class="ident">MemoryDatabase</span>;
1525     <span class="kw">use</span> <span class="kw">crate</span>::<span class="ident">types</span>::<span class="kw-2">*</span>;
1526
1527     <span class="kw">use</span> <span class="ident">rand</span>::<span class="ident">rngs</span>::<span class="ident">StdRng</span>;
1528     <span class="kw">use</span> <span class="ident">rand</span>::<span class="ident">seq</span>::<span class="ident">SliceRandom</span>;
1529     <span class="kw">use</span> <span class="ident">rand</span>::{<span class="ident">Rng</span>, <span class="ident">SeedableRng</span>};
1530
1531     <span class="kw">const</span> <span class="ident">P2WPKH_WITNESS_SIZE</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">73</span> <span class="op">+</span> <span class="number">33</span> <span class="op">+</span> <span class="number">2</span>;
1532
1533     <span class="kw">fn</span> <span class="ident">get_test_utxos</span>() <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span> {
1534         <span class="macro">vec</span><span class="macro">!</span>[
1535             (
1536                 <span class="ident">UTXO</span> {
1537                     <span class="ident">outpoint</span>: <span class="ident">OutPoint</span>::<span class="ident">from_str</span>(
1538                         <span class="string">&quot;ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:0&quot;</span>,
1539                     )
1540                     .<span class="ident">unwrap</span>(),
1541                     <span class="ident">txout</span>: <span class="ident">TxOut</span> {
1542                         <span class="ident">value</span>: <span class="number">100_000</span>,
1543                         <span class="ident">script_pubkey</span>: <span class="ident">Script</span>::<span class="ident">new</span>(),
1544                     },
1545                     <span class="ident">keychain</span>: <span class="ident">KeychainKind</span>::<span class="ident">External</span>,
1546                 },
1547                 <span class="ident">P2WPKH_WITNESS_SIZE</span>,
1548             ),
1549             (
1550                 <span class="ident">UTXO</span> {
1551                     <span class="ident">outpoint</span>: <span class="ident">OutPoint</span>::<span class="ident">from_str</span>(
1552                         <span class="string">&quot;65d92ddff6b6dc72c89624a6491997714b90f6004f928d875bc0fd53f264fa85:0&quot;</span>,
1553                     )
1554                     .<span class="ident">unwrap</span>(),
1555                     <span class="ident">txout</span>: <span class="ident">TxOut</span> {
1556                         <span class="ident">value</span>: <span class="number">200_000</span>,
1557                         <span class="ident">script_pubkey</span>: <span class="ident">Script</span>::<span class="ident">new</span>(),
1558                     },
1559                     <span class="ident">keychain</span>: <span class="ident">KeychainKind</span>::<span class="ident">Internal</span>,
1560                 },
1561                 <span class="ident">P2WPKH_WITNESS_SIZE</span>,
1562             ),
1563         ]
1564     }
1565
1566     <span class="kw">fn</span> <span class="ident">generate_random_utxos</span>(<span class="ident">rng</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">StdRng</span>, <span class="ident">utxos_number</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span> {
1567         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">res</span> <span class="op">=</span> <span class="ident">Vec</span>::<span class="ident">new</span>();
1568         <span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">utxos_number</span> {
1569             <span class="ident">res</span>.<span class="ident">push</span>((
1570                 <span class="ident">UTXO</span> {
1571                     <span class="ident">outpoint</span>: <span class="ident">OutPoint</span>::<span class="ident">from_str</span>(
1572                         <span class="string">&quot;ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:0&quot;</span>,
1573                     )
1574                     .<span class="ident">unwrap</span>(),
1575                     <span class="ident">txout</span>: <span class="ident">TxOut</span> {
1576                         <span class="ident">value</span>: <span class="ident">rng</span>.<span class="ident">gen_range</span>(<span class="number">0</span>, <span class="number">200000000</span>),
1577                         <span class="ident">script_pubkey</span>: <span class="ident">Script</span>::<span class="ident">new</span>(),
1578                     },
1579                     <span class="ident">keychain</span>: <span class="ident">KeychainKind</span>::<span class="ident">External</span>,
1580                 },
1581                 <span class="ident">P2WPKH_WITNESS_SIZE</span>,
1582             ));
1583         }
1584         <span class="ident">res</span>
1585     }
1586
1587     <span class="kw">fn</span> <span class="ident">generate_same_value_utxos</span>(<span class="ident">utxos_value</span>: <span class="ident">u64</span>, <span class="ident">utxos_number</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span> {
1588         <span class="kw">let</span> <span class="ident">utxo</span> <span class="op">=</span> (
1589             <span class="ident">UTXO</span> {
1590                 <span class="ident">outpoint</span>: <span class="ident">OutPoint</span>::<span class="ident">from_str</span>(
1591                     <span class="string">&quot;ebd9813ecebc57ff8f30797de7c205e3c7498ca950ea4341ee51a685ff2fa30a:0&quot;</span>,
1592                 )
1593                 .<span class="ident">unwrap</span>(),
1594                 <span class="ident">txout</span>: <span class="ident">TxOut</span> {
1595                     <span class="ident">value</span>: <span class="ident">utxos_value</span>,
1596                     <span class="ident">script_pubkey</span>: <span class="ident">Script</span>::<span class="ident">new</span>(),
1597                 },
1598                 <span class="ident">keychain</span>: <span class="ident">KeychainKind</span>::<span class="ident">External</span>,
1599             },
1600             <span class="ident">P2WPKH_WITNESS_SIZE</span>,
1601         );
1602         <span class="macro">vec</span><span class="macro">!</span>[<span class="ident">utxo</span>; <span class="ident">utxos_number</span>]
1603     }
1604
1605     <span class="kw">fn</span> <span class="ident">sum_random_utxos</span>(<span class="kw-2">mut</span> <span class="ident">rng</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">StdRng</span>, <span class="ident">utxos</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">UTXO</span>, <span class="ident">usize</span>)<span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">u64</span> {
1606         <span class="kw">let</span> <span class="ident">utxos_picked_len</span> <span class="op">=</span> <span class="ident">rng</span>.<span class="ident">gen_range</span>(<span class="number">2</span>, <span class="ident">utxos</span>.<span class="ident">len</span>() <span class="op">/</span> <span class="number">2</span>);
1607         <span class="ident">utxos</span>.<span class="ident">shuffle</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>);
1608         <span class="ident">utxos</span>[..<span class="ident">utxos_picked_len</span>]
1609             .<span class="ident">iter</span>()
1610             .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="number">0</span>.<span class="ident">txout</span>.<span class="ident">value</span>)
1611     }
1612
1613     <span class="attribute">#[<span class="ident">test</span>]</span>
1614     <span class="kw">fn</span> <span class="ident">test_largest_first_coin_selection_success</span>() {
1615         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1616         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1617
1618         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">LargestFirstCoinSelection</span>::<span class="ident">default</span>()
1619             .<span class="ident">coin_select</span>(
1620                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1621                 <span class="ident">utxos</span>,
1622                 <span class="macro">vec</span><span class="macro">!</span>[],
1623                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1624                 <span class="number">250_000</span>,
1625                 <span class="number">50.0</span>,
1626             )
1627             .<span class="ident">unwrap</span>();
1628
1629         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>(), <span class="number">2</span>);
1630         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">300_000</span>);
1631         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">fee_amount</span>, <span class="number">186.0</span>);
1632     }
1633
1634     <span class="attribute">#[<span class="ident">test</span>]</span>
1635     <span class="kw">fn</span> <span class="ident">test_largest_first_coin_selection_use_all</span>() {
1636         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1637         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1638
1639         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">LargestFirstCoinSelection</span>::<span class="ident">default</span>()
1640             .<span class="ident">coin_select</span>(
1641                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1642                 <span class="ident">utxos</span>,
1643                 <span class="macro">vec</span><span class="macro">!</span>[],
1644                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1645                 <span class="number">20_000</span>,
1646                 <span class="number">50.0</span>,
1647             )
1648             .<span class="ident">unwrap</span>();
1649
1650         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>(), <span class="number">2</span>);
1651         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">300_000</span>);
1652         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">fee_amount</span>, <span class="number">186.0</span>);
1653     }
1654
1655     <span class="attribute">#[<span class="ident">test</span>]</span>
1656     <span class="kw">fn</span> <span class="ident">test_largest_first_coin_selection_use_only_necessary</span>() {
1657         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1658         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1659
1660         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">LargestFirstCoinSelection</span>::<span class="ident">default</span>()
1661             .<span class="ident">coin_select</span>(
1662                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1663                 <span class="macro">vec</span><span class="macro">!</span>[],
1664                 <span class="ident">utxos</span>,
1665                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1666                 <span class="number">20_000</span>,
1667                 <span class="number">50.0</span>,
1668             )
1669             .<span class="ident">unwrap</span>();
1670
1671         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>(), <span class="number">1</span>);
1672         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">200_000</span>);
1673         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">fee_amount</span>, <span class="number">118.0</span>);
1674     }
1675
1676     <span class="attribute">#[<span class="ident">test</span>]</span>
1677     <span class="attribute">#[<span class="ident">should_panic</span>(<span class="ident">expected</span> <span class="op">=</span> <span class="string">&quot;InsufficientFunds&quot;</span>)]</span>
1678     <span class="kw">fn</span> <span class="ident">test_largest_first_coin_selection_insufficient_funds</span>() {
1679         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1680         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1681
1682         <span class="ident">LargestFirstCoinSelection</span>::<span class="ident">default</span>()
1683             .<span class="ident">coin_select</span>(
1684                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1685                 <span class="macro">vec</span><span class="macro">!</span>[],
1686                 <span class="ident">utxos</span>,
1687                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1688                 <span class="number">500_000</span>,
1689                 <span class="number">50.0</span>,
1690             )
1691             .<span class="ident">unwrap</span>();
1692     }
1693
1694     <span class="attribute">#[<span class="ident">test</span>]</span>
1695     <span class="attribute">#[<span class="ident">should_panic</span>(<span class="ident">expected</span> <span class="op">=</span> <span class="string">&quot;InsufficientFunds&quot;</span>)]</span>
1696     <span class="kw">fn</span> <span class="ident">test_largest_first_coin_selection_insufficient_funds_high_fees</span>() {
1697         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1698         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1699
1700         <span class="ident">LargestFirstCoinSelection</span>::<span class="ident">default</span>()
1701             .<span class="ident">coin_select</span>(
1702                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1703                 <span class="macro">vec</span><span class="macro">!</span>[],
1704                 <span class="ident">utxos</span>,
1705                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1000.0</span>),
1706                 <span class="number">250_000</span>,
1707                 <span class="number">50.0</span>,
1708             )
1709             .<span class="ident">unwrap</span>();
1710     }
1711
1712     <span class="attribute">#[<span class="ident">test</span>]</span>
1713     <span class="kw">fn</span> <span class="ident">test_bnb_coin_selection_success</span>() {
1714         <span class="comment">// In this case bnb won&#39;t find a suitable match and single random draw will</span>
1715         <span class="comment">// select three outputs</span>
1716         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">generate_same_value_utxos</span>(<span class="number">100_000</span>, <span class="number">20</span>);
1717
1718         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1719
1720         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">default</span>()
1721             .<span class="ident">coin_select</span>(
1722                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1723                 <span class="macro">vec</span><span class="macro">!</span>[],
1724                 <span class="ident">utxos</span>,
1725                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1726                 <span class="number">250_000</span>,
1727                 <span class="number">50.0</span>,
1728             )
1729             .<span class="ident">unwrap</span>();
1730
1731         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>(), <span class="number">3</span>);
1732         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">300_000</span>);
1733         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">fee_amount</span>, <span class="number">254.0</span>);
1734     }
1735
1736     <span class="attribute">#[<span class="ident">test</span>]</span>
1737     <span class="kw">fn</span> <span class="ident">test_bnb_coin_selection_required_are_enough</span>() {
1738         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1739         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1740
1741         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">default</span>()
1742             .<span class="ident">coin_select</span>(
1743                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1744                 <span class="ident">utxos</span>.<span class="ident">clone</span>(),
1745                 <span class="ident">utxos</span>,
1746                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1747                 <span class="number">20_000</span>,
1748                 <span class="number">50.0</span>,
1749             )
1750             .<span class="ident">unwrap</span>();
1751
1752         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>(), <span class="number">2</span>);
1753         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">300_000</span>);
1754         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">fee_amount</span>, <span class="number">186.0</span>);
1755     }
1756
1757     <span class="attribute">#[<span class="ident">test</span>]</span>
1758     <span class="attribute">#[<span class="ident">should_panic</span>(<span class="ident">expected</span> <span class="op">=</span> <span class="string">&quot;InsufficientFunds&quot;</span>)]</span>
1759     <span class="kw">fn</span> <span class="ident">test_bnb_coin_selection_insufficient_funds</span>() {
1760         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1761         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1762
1763         <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">default</span>()
1764             .<span class="ident">coin_select</span>(
1765                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1766                 <span class="macro">vec</span><span class="macro">!</span>[],
1767                 <span class="ident">utxos</span>,
1768                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1769                 <span class="number">500_000</span>,
1770                 <span class="number">50.0</span>,
1771             )
1772             .<span class="ident">unwrap</span>();
1773     }
1774
1775     <span class="attribute">#[<span class="ident">test</span>]</span>
1776     <span class="attribute">#[<span class="ident">should_panic</span>(<span class="ident">expected</span> <span class="op">=</span> <span class="string">&quot;InsufficientFunds&quot;</span>)]</span>
1777     <span class="kw">fn</span> <span class="ident">test_bnb_coin_selection_insufficient_funds_high_fees</span>() {
1778         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1779         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1780
1781         <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">default</span>()
1782             .<span class="ident">coin_select</span>(
1783                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1784                 <span class="macro">vec</span><span class="macro">!</span>[],
1785                 <span class="ident">utxos</span>,
1786                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1000.0</span>),
1787                 <span class="number">250_000</span>,
1788                 <span class="number">50.0</span>,
1789             )
1790             .<span class="ident">unwrap</span>();
1791     }
1792
1793     <span class="attribute">#[<span class="ident">test</span>]</span>
1794     <span class="kw">fn</span> <span class="ident">test_bnb_coin_selection_check_fee_rate</span>() {
1795         <span class="kw">let</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>();
1796         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1797
1798         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">new</span>(<span class="number">0</span>)
1799             .<span class="ident">coin_select</span>(
1800                 <span class="kw-2">&amp;</span><span class="ident">database</span>,
1801                 <span class="macro">vec</span><span class="macro">!</span>[],
1802                 <span class="ident">utxos</span>.<span class="ident">clone</span>(),
1803                 <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>),
1804                 <span class="number">99932</span>, <span class="comment">// first utxo&#39;s effective value</span>
1805                 <span class="number">0.0</span>,
1806             )
1807             .<span class="ident">unwrap</span>();
1808
1809         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>(), <span class="number">1</span>);
1810         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">100_000</span>);
1811         <span class="kw">let</span> <span class="ident">input_size</span> <span class="op">=</span> (<span class="ident">TXIN_BASE_WEIGHT</span> <span class="kw">as</span> <span class="ident">f32</span>) <span class="op">/</span> <span class="number">4.0</span> <span class="op">+</span> <span class="ident">P2WPKH_WITNESS_SIZE</span> <span class="kw">as</span> <span class="ident">f32</span> <span class="op">/</span> <span class="number">4.0</span>;
1812         <span class="kw">let</span> <span class="ident">epsilon</span> <span class="op">=</span> <span class="number">0.5</span>;
1813         <span class="macro">assert</span><span class="macro">!</span>((<span class="number">1.0</span> <span class="op">-</span> (<span class="ident">result</span>.<span class="ident">fee_amount</span> <span class="op">/</span> <span class="ident">input_size</span>)).<span class="ident">abs</span>() <span class="op">&lt;</span> <span class="ident">epsilon</span>);
1814     }
1815
1816     <span class="attribute">#[<span class="ident">test</span>]</span>
1817     <span class="kw">fn</span> <span class="ident">test_bnb_coin_selection_exact_match</span>() {
1818         <span class="kw">let</span> <span class="ident">seed</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">32</span>];
1819         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span>: <span class="ident">StdRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>(<span class="ident">seed</span>);
1820         <span class="kw">let</span> <span class="ident">database</span> <span class="op">=</span> <span class="ident">MemoryDatabase</span>::<span class="ident">default</span>();
1821
1822         <span class="kw">for</span> <span class="ident">_i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="number">200</span> {
1823             <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">optional_utxos</span> <span class="op">=</span> <span class="ident">generate_random_utxos</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>, <span class="number">16</span>);
1824             <span class="kw">let</span> <span class="ident">target_amount</span> <span class="op">=</span> <span class="ident">sum_random_utxos</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">optional_utxos</span>);
1825             <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">new</span>(<span class="number">0</span>)
1826                 .<span class="ident">coin_select</span>(
1827                     <span class="kw-2">&amp;</span><span class="ident">database</span>,
1828                     <span class="macro">vec</span><span class="macro">!</span>[],
1829                     <span class="ident">optional_utxos</span>,
1830                     <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">0.0</span>),
1831                     <span class="ident">target_amount</span>,
1832                     <span class="number">0.0</span>,
1833                 )
1834                 .<span class="ident">unwrap</span>();
1835             <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="ident">target_amount</span>);
1836         }
1837     }
1838
1839     <span class="attribute">#[<span class="ident">test</span>]</span>
1840     <span class="attribute">#[<span class="ident">should_panic</span>(<span class="ident">expected</span> <span class="op">=</span> <span class="string">&quot;BnBNoExactMatch&quot;</span>)]</span>
1841     <span class="kw">fn</span> <span class="ident">test_bnb_function_no_exact_match</span>() {
1842         <span class="kw">let</span> <span class="ident">fee_rate</span> <span class="op">=</span> <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">10.0</span>);
1843         <span class="kw">let</span> <span class="ident">utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">get_test_utxos</span>()
1844             .<span class="ident">into_iter</span>()
1845             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1846             .<span class="ident">collect</span>();
1847
1848         <span class="kw">let</span> <span class="ident">curr_available_value</span> <span class="op">=</span> <span class="ident">utxos</span>
1849             .<span class="ident">iter</span>()
1850             .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>);
1851
1852         <span class="kw">let</span> <span class="ident">size_of_change</span> <span class="op">=</span> <span class="number">31</span>;
1853         <span class="kw">let</span> <span class="ident">cost_of_change</span> <span class="op">=</span> <span class="ident">size_of_change</span> <span class="kw">as</span> <span class="ident">f32</span> <span class="op">*</span> <span class="ident">fee_rate</span>.<span class="ident">as_sat_vb</span>();
1854         <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">new</span>(<span class="ident">size_of_change</span>)
1855             .<span class="ident">bnb</span>(
1856                 <span class="macro">vec</span><span class="macro">!</span>[],
1857                 <span class="ident">utxos</span>,
1858                 <span class="number">0</span>,
1859                 <span class="ident">curr_available_value</span>,
1860                 <span class="number">20_000</span>,
1861                 <span class="number">50.0</span>,
1862                 <span class="ident">cost_of_change</span>,
1863             )
1864             .<span class="ident">unwrap</span>();
1865     }
1866
1867     <span class="attribute">#[<span class="ident">test</span>]</span>
1868     <span class="attribute">#[<span class="ident">should_panic</span>(<span class="ident">expected</span> <span class="op">=</span> <span class="string">&quot;BnBTotalTriesExceeded&quot;</span>)]</span>
1869     <span class="kw">fn</span> <span class="ident">test_bnb_function_tries_exceeded</span>() {
1870         <span class="kw">let</span> <span class="ident">fee_rate</span> <span class="op">=</span> <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">10.0</span>);
1871         <span class="kw">let</span> <span class="ident">utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">generate_same_value_utxos</span>(<span class="number">100_000</span>, <span class="number">100_000</span>)
1872             .<span class="ident">into_iter</span>()
1873             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1874             .<span class="ident">collect</span>();
1875
1876         <span class="kw">let</span> <span class="ident">curr_available_value</span> <span class="op">=</span> <span class="ident">utxos</span>
1877             .<span class="ident">iter</span>()
1878             .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>);
1879
1880         <span class="kw">let</span> <span class="ident">size_of_change</span> <span class="op">=</span> <span class="number">31</span>;
1881         <span class="kw">let</span> <span class="ident">cost_of_change</span> <span class="op">=</span> <span class="ident">size_of_change</span> <span class="kw">as</span> <span class="ident">f32</span> <span class="op">*</span> <span class="ident">fee_rate</span>.<span class="ident">as_sat_vb</span>();
1882
1883         <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">new</span>(<span class="ident">size_of_change</span>)
1884             .<span class="ident">bnb</span>(
1885                 <span class="macro">vec</span><span class="macro">!</span>[],
1886                 <span class="ident">utxos</span>,
1887                 <span class="number">0</span>,
1888                 <span class="ident">curr_available_value</span>,
1889                 <span class="number">20_000</span>,
1890                 <span class="number">50.0</span>,
1891                 <span class="ident">cost_of_change</span>,
1892             )
1893             .<span class="ident">unwrap</span>();
1894     }
1895
1896     <span class="comment">// The match won&#39;t be exact but still in the range</span>
1897     <span class="attribute">#[<span class="ident">test</span>]</span>
1898     <span class="kw">fn</span> <span class="ident">test_bnb_function_almost_exact_match_with_fees</span>() {
1899         <span class="kw">let</span> <span class="ident">fee_rate</span> <span class="op">=</span> <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>);
1900         <span class="kw">let</span> <span class="ident">size_of_change</span> <span class="op">=</span> <span class="number">31</span>;
1901         <span class="kw">let</span> <span class="ident">cost_of_change</span> <span class="op">=</span> <span class="ident">size_of_change</span> <span class="kw">as</span> <span class="ident">f32</span> <span class="op">*</span> <span class="ident">fee_rate</span>.<span class="ident">as_sat_vb</span>();
1902         <span class="kw">let</span> <span class="ident">fee_amount</span> <span class="op">=</span> <span class="number">50.0</span>;
1903
1904         <span class="kw">let</span> <span class="ident">utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">generate_same_value_utxos</span>(<span class="number">50_000</span>, <span class="number">10</span>)
1905             .<span class="ident">into_iter</span>()
1906             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1907             .<span class="ident">collect</span>();
1908
1909         <span class="kw">let</span> <span class="ident">curr_value</span> <span class="op">=</span> <span class="number">0</span>;
1910
1911         <span class="kw">let</span> <span class="ident">curr_available_value</span> <span class="op">=</span> <span class="ident">utxos</span>
1912             .<span class="ident">iter</span>()
1913             .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>);
1914
1915         <span class="comment">// 2*(value of 1 utxo)  - 2*(1 utxo fees with 1.0sat/vbyte fee rate) -</span>
1916         <span class="comment">// cost_of_change + 5.</span>
1917         <span class="kw">let</span> <span class="ident">target_amount</span> <span class="op">=</span> <span class="number">2</span> <span class="op">*</span> <span class="number">50_000</span> <span class="op">-</span> <span class="number">2</span> <span class="op">*</span> <span class="number">67</span> <span class="op">-</span> <span class="ident">cost_of_change</span>.<span class="ident">ceil</span>() <span class="kw">as</span> <span class="ident">u64</span> <span class="op">+</span> <span class="number">5</span>;
1918
1919         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">new</span>(<span class="ident">size_of_change</span>)
1920             .<span class="ident">bnb</span>(
1921                 <span class="macro">vec</span><span class="macro">!</span>[],
1922                 <span class="ident">utxos</span>,
1923                 <span class="ident">curr_value</span>,
1924                 <span class="ident">curr_available_value</span>,
1925                 <span class="ident">target_amount</span>,
1926                 <span class="ident">fee_amount</span>,
1927                 <span class="ident">cost_of_change</span>,
1928             )
1929             .<span class="ident">unwrap</span>();
1930         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">fee_amount</span>, <span class="number">186.0</span>);
1931         <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="number">100_000</span>);
1932     }
1933
1934     <span class="comment">// TODO: bnb() function should be optimized, and this test should be done with more utxos</span>
1935     <span class="attribute">#[<span class="ident">test</span>]</span>
1936     <span class="kw">fn</span> <span class="ident">test_bnb_function_exact_match_more_utxos</span>() {
1937         <span class="kw">let</span> <span class="ident">seed</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">32</span>];
1938         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span>: <span class="ident">StdRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>(<span class="ident">seed</span>);
1939         <span class="kw">let</span> <span class="ident">fee_rate</span> <span class="op">=</span> <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">0.0</span>);
1940
1941         <span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..<span class="number">200</span> {
1942             <span class="kw">let</span> <span class="ident">optional_utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="kw">_</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">generate_random_utxos</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>, <span class="number">40</span>)
1943                 .<span class="ident">into_iter</span>()
1944                 .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1945                 .<span class="ident">collect</span>();
1946
1947             <span class="kw">let</span> <span class="ident">curr_value</span> <span class="op">=</span> <span class="number">0</span>;
1948
1949             <span class="kw">let</span> <span class="ident">curr_available_value</span> <span class="op">=</span> <span class="ident">optional_utxos</span>
1950                 .<span class="ident">iter</span>()
1951                 .<span class="ident">fold</span>(<span class="number">0</span>, <span class="op">|</span><span class="ident">acc</span>, <span class="ident">x</span><span class="op">|</span> <span class="ident">acc</span> <span class="op">+</span> <span class="ident">x</span>.<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>);
1952
1953             <span class="kw">let</span> <span class="ident">target_amount</span> <span class="op">=</span> <span class="ident">optional_utxos</span>[<span class="number">3</span>].<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>
1954                 <span class="op">+</span> <span class="ident">optional_utxos</span>[<span class="number">23</span>].<span class="ident">effective_value</span> <span class="kw">as</span> <span class="ident">u64</span>;
1955
1956             <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">new</span>(<span class="number">0</span>)
1957                 .<span class="ident">bnb</span>(
1958                     <span class="macro">vec</span><span class="macro">!</span>[],
1959                     <span class="ident">optional_utxos</span>,
1960                     <span class="ident">curr_value</span>,
1961                     <span class="ident">curr_available_value</span>,
1962                     <span class="ident">target_amount</span>,
1963                     <span class="number">0.0</span>,
1964                     <span class="number">0.0</span>,
1965                 )
1966                 .<span class="ident">unwrap</span>();
1967             <span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span>, <span class="ident">target_amount</span>);
1968         }
1969     }
1970
1971     <span class="attribute">#[<span class="ident">test</span>]</span>
1972     <span class="kw">fn</span> <span class="ident">test_single_random_draw_function_success</span>() {
1973         <span class="kw">let</span> <span class="ident">seed</span> <span class="op">=</span> [<span class="number">0</span>; <span class="number">32</span>];
1974         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span>: <span class="ident">StdRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>(<span class="ident">seed</span>);
1975         <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">utxos</span> <span class="op">=</span> <span class="ident">generate_random_utxos</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>, <span class="number">300</span>);
1976         <span class="kw">let</span> <span class="ident">target_amount</span> <span class="op">=</span> <span class="ident">sum_random_utxos</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">rng</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">utxos</span>);
1977
1978         <span class="kw">let</span> <span class="ident">fee_rate</span> <span class="op">=</span> <span class="ident">FeeRate</span>::<span class="ident">from_sat_per_vb</span>(<span class="number">1.0</span>);
1979         <span class="kw">let</span> <span class="ident">utxos</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">OutputGroup</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">utxos</span>
1980             .<span class="ident">into_iter</span>()
1981             .<span class="ident">map</span>(<span class="op">|</span><span class="ident">u</span><span class="op">|</span> <span class="ident">OutputGroup</span>::<span class="ident">new</span>(<span class="ident">u</span>.<span class="number">0</span>, <span class="ident">u</span>.<span class="number">1</span>, <span class="ident">fee_rate</span>))
1982             .<span class="ident">collect</span>();
1983
1984         <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">BranchAndBoundCoinSelection</span>::<span class="ident">default</span>().<span class="ident">single_random_draw</span>(
1985             <span class="macro">vec</span><span class="macro">!</span>[],
1986             <span class="ident">utxos</span>,
1987             <span class="number">0</span>,
1988             <span class="ident">target_amount</span>,
1989             <span class="number">50.0</span>,
1990         );
1991
1992         <span class="macro">assert</span><span class="macro">!</span>(<span class="ident">result</span>.<span class="ident">selected_amount</span> <span class="op">&gt;</span> <span class="ident">target_amount</span>);
1993         <span class="macro">assert_eq</span><span class="macro">!</span>(
1994             <span class="ident">result</span>.<span class="ident">fee_amount</span>,
1995             <span class="number">50.0</span> <span class="op">+</span> <span class="ident">result</span>.<span class="ident">selected</span>.<span class="ident">len</span>() <span class="kw">as</span> <span class="ident">f32</span> <span class="op">*</span> <span class="number">68.0</span>
1996         );
1997     }
1998 }
1999 </pre></div>
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