coinselection: Add CoinGrinder algorithm

CoinGrinder is a DFS-based coin selection algorithm that
deterministically finds the input set with the lowest weight creating a
change output.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp
index b51cd6332f..c79079d33d 100644
--- a/src/wallet/spend.cpp
+++ b/src/wallet/spend.cpp
@@ -709,6 +709,15 @@ util::Result<SelectionResult> ChooseSelectionResult(interfaces::Chain& chain, co
         results.push_back(*knapsack_result);
     } else append_error(knapsack_result);
 
+    if (coin_selection_params.m_effective_feerate > CFeeRate{3 * coin_selection_params.m_long_term_feerate}) { // Minimize input set for feerates of at least 3×LTFRE (default: 30 ṩ/vB+)
+        if (auto cg_result{CoinGrinder(groups.positive_group, nTargetValue, coin_selection_params.m_min_change_target, max_inputs_weight)}) {
+            cg_result->ComputeAndSetWaste(coin_selection_params.min_viable_change, coin_selection_params.m_cost_of_change, coin_selection_params.m_change_fee);
+            results.push_back(*cg_result);
+        } else {
+            append_error(cg_result);
+        }
+    }
+
     if (auto srd_result{SelectCoinsSRD(groups.positive_group, nTargetValue, coin_selection_params.m_change_fee, coin_selection_params.rng_fast, max_inputs_weight)}) {
         results.push_back(*srd_result);
     } else append_error(srd_result);