[wallet] remove MIN_CHANGE

Author: glozow

src/bench/coin_selection.cpp

@@ -13,13 +13,13 @@
 
 using node::NodeContext;
 using wallet::AttemptSelection;
+using wallet::CHANGE_LOWER;
 using wallet::COutput;
 using wallet::CWallet;
 using wallet::CWalletTx;
 using wallet::CoinEligibilityFilter;
 using wallet::CoinSelectionParams;
 using wallet::CreateDummyWalletDatabase;
-using wallet::MIN_CHANGE;
 using wallet::OutputGroup;
 using wallet::SelectCoinsBnB;
 using wallet::TxStateInactive;
@@ -67,7 +67,7 @@ static void CoinSelection(benchmark::Bench& bench)
         rand,
         /* change_output_size= */ 34,
         /* change_spend_size= */ 148,
-        /*min_change_target=*/ MIN_CHANGE,
+        /*min_change_target=*/ CHANGE_LOWER,
         /* effective_feerate= */ CFeeRate(0),
         /* long_term_feerate= */ CFeeRate(0),
         /* discard_feerate= */ CFeeRate(0),

src/qt/coincontroldialog.cpp

@@ -32,7 +32,6 @@
 #include <QTreeWidget>
 
 using wallet::CCoinControl;
-using wallet::MIN_CHANGE;
 
 QList<CAmount> CoinControlDialog::payAmounts;
 bool CoinControlDialog::fSubtractFeeFromAmount = false;
@@ -485,11 +484,10 @@ void CoinControlDialog::updateLabels(CCoinControl& m_coin_control, WalletModel *
             if (!CoinControlDialog::fSubtractFeeFromAmount)
                 nChange -= nPayFee;
 
-            // Never create dust outputs; if we would, just add the dust to the fee.
-            if (nChange > 0 && nChange < MIN_CHANGE)
-            {
+            if (nChange > 0) {
                 // Assumes a p2pkh script size
                 CTxOut txout(nChange, CScript() << std::vector<unsigned char>(24, 0));
+                // Never create dust outputs; if we would, just add the dust to the fee.
                 if (IsDust(txout, model->node().getDustRelayFee()))
                 {
                     nPayFee += nChange;

src/wallet/coinselection.h

@@ -13,18 +13,10 @@
 #include <optional>
 
 namespace wallet {
-//! target minimum change amount
-static constexpr CAmount MIN_CHANGE{COIN / 100};
-//! final minimum change amount after paying for fees
-static const CAmount MIN_FINAL_CHANGE = MIN_CHANGE/2;
 //! lower bound for randomly-chosen target change amount
 static constexpr CAmount CHANGE_LOWER{50000};
 //! upper bound for randomly-chosen target change amount
 static constexpr CAmount CHANGE_UPPER{1000000};
-// Ensure that any randomly generated change targets are less than or equal to before.
-// Otherwise, tests may fail if funds are not enough to cover change.
-static_assert(CHANGE_UPPER <= MIN_CHANGE);
-static_assert(CHANGE_LOWER <= MIN_FINAL_CHANGE);
 
 /** A UTXO under consideration for use in funding a new transaction. */
 class COutput
@@ -104,7 +96,7 @@ struct CoinSelectionParams {
     size_t change_spend_size = 0;
     /** Mininmum change to target in Knapsack solver: select coins to cover the payment and
      * at least this value of change. */
-    CAmount m_min_change_target{MIN_CHANGE};
+    CAmount m_min_change_target{0};
     /** Cost of creating the change output. */
     CAmount m_change_fee{0};
     /** The pre-determined minimum value to target when funding a change output. */