opt: Skip checking max_weight separately

Init best_selection_weight as max_weight allows us to skip the separate max_weight check on every loop.
murchandamus · Sep 26, 2023 · dc6fe3a · dc6fe3a
1 parent 6ba9c1c
commit dc6fe3a
Showing 1 changed file with 4 additions and 10 deletions.
diff --git a/src/wallet/coinselection.cpp b/src/wallet/coinselection.cpp
@@ -246,7 +246,7 @@ util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, c
 
     std::vector<size_t> best_selection; // best selection UTXO indices
     CAmount best_selection_amount = MAX_MONEY;
-    int best_selection_weight = INT_MAX;
+    int best_selection_weight = max_weight; // Tie is fine, because we prefer lower selection amount
 
     std::vector<size_t> curr_selection; // selected UTXO indices
     CAmount curr_amount = 0;
@@ -350,15 +350,9 @@ util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, c
             if (curr_amount + lookahead.at(utxo_pool_index) < selection_target + change_target) {
                 // Cannot succeed due to insufficient funds in lookahead: CUT (deselect latest, SHIFT)
                 next_op = operations::cut;
-            } else if (curr_weight > max_weight) {
-                // max_weight exceeded: CUT if last selected group had minimal weight, else SHIFT
-                max_tx_weight_exceeded = true;
-                if (utxo_pool.at(curr_selection.back()).m_weight <= min_tail_weight.at(curr_selection.back())) {
-                    next_op = operations::cut;
-                } else {
-                    next_op = operations::shift;
-                }
             } else if (curr_weight > best_selection_weight) {
+                // best_selection_weight is initialized to max_weight
+                if (curr_weight > max_weight) max_tx_weight_exceeded = true;
                 // Worse weight than best solution. More UTXOs only increase weight:
                 // CUT if last selected group had minimal weight, else SHIFT
                 if (utxo_pool.at(curr_selection.back()).m_weight <= min_tail_weight.at(curr_selection.back())) {
@@ -369,7 +363,7 @@ util::Result<SelectionResult> CoinGrinder(std::vector<OutputGroup>& utxo_pool, c
             } else if (curr_amount >= selection_target + change_target) {
                 // Target exceeded: check if new best, then SHIFT (deselect latest, select next)
                 next_op = operations::shift;
-                if (curr_weight < best_selection_weight || (curr_weight == best_selection_weight && curr_amount < best_selection_amount)) {
+                if (curr_weight < best_selection_weight || curr_amount < best_selection_amount) {
                     best_selection = curr_selection;
                     best_selection_weight = curr_weight;
                     best_selection_amount = curr_amount;