merge bitcoin#17331: Use effective values throughout coin selection

excludes:
- 1bf4a62
- af5867c
- d97d25d
- cc3f14b

src/bench/coin_selection.cpp

@@ -48,15 +48,14 @@ static void CoinSelection(benchmark::Bench& bench)
         coins.emplace_back(wtx.get(), 0 /* iIn */, 6 * 24 /* nDepthIn */, true /* spendable */, true /* solvable */, true /* safe */);
     }
     const CoinEligibilityFilter filter_standard(1, 6, 0);
-    const CoinSelectionParams coin_selection_params(/* use_bnb= */ true, /* change_output_size= */ 34,
+    const CoinSelectionParams coin_selection_params(/* change_output_size= */ 34,
                                                     /* change_spend_size= */ 148, /* effective_feerate= */ CFeeRate(0),
                                                     /* long_term_feerate= */ CFeeRate(0), /* discard_feerate= */ CFeeRate(0),
                                                     /* tx_no_inputs_size= */ 0, /* avoid_partial= */ false);
     bench.run([&] {
         std::set<CInputCoin> setCoinsRet;
         CAmount nValueRet;
-        bool bnb_used;
-        bool success = wallet.SelectCoinsMinConf(1003 * COIN, filter_standard, coins, setCoinsRet, nValueRet, coin_selection_params, bnb_used);
+        bool success = wallet.SelectCoinsMinConf(1003 * COIN, filter_standard, coins, setCoinsRet, nValueRet, coin_selection_params);
         assert(success);
         assert(nValueRet == 1003 * COIN);
         assert(setCoinsRet.size() == 2);
@@ -94,12 +93,11 @@ static void BnBExhaustion(benchmark::Bench& bench)
     std::vector<OutputGroup> utxo_pool;
     CoinSet selection;
     CAmount value_ret = 0;
-    CAmount not_input_fees = 0;
 
     bench.run([&] {
         // Benchmark
         CAmount target = make_hard_case(17, utxo_pool);
-        SelectCoinsBnB(utxo_pool, target, 0, selection, value_ret, not_input_fees); // Should exhaust
+        SelectCoinsBnB(utxo_pool, target, 0, selection, value_ret); // Should exhaust
 
         // Cleanup
         utxo_pool.clear();

src/wallet/coinselection.cpp

@@ -16,7 +16,7 @@
 struct {
     bool operator()(const OutputGroup& a, const OutputGroup& b) const
     {
-        return a.effective_value > b.effective_value;
+        return a.GetSelectionAmount() > b.GetSelectionAmount();
     }
 } descending;
 
@@ -51,35 +51,32 @@ struct {
  * @param const std::vector<CInputCoin>& utxo_pool The set of UTXOs that we are choosing from.
  *        These UTXOs will be sorted in descending order by effective value and the CInputCoins'
  *        values are their effective values.
- * @param const CAmount& target_value This is the value that we want to select. It is the lower
+ * @param const CAmount& selection_target This is the value that we want to select. It is the lower
  *        bound of the range.
  * @param const CAmount& cost_of_change This is the cost of creating and spending a change output.
- *        This plus target_value is the upper bound of the range.
+ *        This plus selection_target is the upper bound of the range.
  * @param std::set<CInputCoin>& out_set -> This is an output parameter for the set of CInputCoins
  *        that have been selected.
  * @param CAmount& value_ret -> This is an output parameter for the total value of the CInputCoins
  *        that were selected.
- * @param CAmount not_input_fees -> The fees that need to be paid for the outputs and fixed size
- *        overhead (version, locktime, marker and flag)
  */
 
 static const size_t TOTAL_TRIES = 100000;
 
-bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& target_value, const CAmount& cost_of_change, std::set<CInputCoin>& out_set, CAmount& value_ret, CAmount not_input_fees)
+bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, const CAmount& cost_of_change, std::set<CInputCoin>& out_set, CAmount& value_ret)
 {
     out_set.clear();
     CAmount curr_value = 0;
 
     std::vector<bool> curr_selection; // select the utxo at this index
     curr_selection.reserve(utxo_pool.size());
-    CAmount selection_target = not_input_fees + target_value;
 
     // Calculate curr_available_value
     CAmount curr_available_value = 0;
     for (const OutputGroup& utxo : utxo_pool) {
         // Assert that this utxo is not negative. It should never be negative, effective value calculation should have removed it
-        assert(utxo.effective_value > 0);
-        curr_available_value += utxo.effective_value;
+        assert(utxo.GetSelectionAmount() > 0);
+        curr_available_value += utxo.GetSelectionAmount();
     }
     if (curr_available_value < selection_target) {
         return false;
@@ -123,7 +120,7 @@ bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& target_v
             // Walk backwards to find the last included UTXO that still needs to have its omission branch traversed.
             while (!curr_selection.empty() && !curr_selection.back()) {
                 curr_selection.pop_back();
-                curr_available_value += utxo_pool.at(curr_selection.size()).effective_value;
+                curr_available_value += utxo_pool.at(curr_selection.size()).GetSelectionAmount();
             }
 
             if (curr_selection.empty()) { // We have walked back to the first utxo and no branch is untraversed. All solutions searched
@@ -133,24 +130,24 @@ bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& target_v
             // Output was included on previous iterations, try excluding now.
             curr_selection.back() = false;
             OutputGroup& utxo = utxo_pool.at(curr_selection.size() - 1);
-            curr_value -= utxo.effective_value;
+            curr_value -= utxo.GetSelectionAmount();
             curr_waste -= utxo.fee - utxo.long_term_fee;
         } else { // Moving forwards, continuing down this branch
             OutputGroup& utxo = utxo_pool.at(curr_selection.size());
 
             // Remove this utxo from the curr_available_value utxo amount
-            curr_available_value -= utxo.effective_value;
+            curr_available_value -= utxo.GetSelectionAmount();
 
             // Avoid searching a branch if the previous UTXO has the same value and same waste and was excluded. Since the ratio of fee to
             // long term fee is the same, we only need to check if one of those values match in order to know that the waste is the same.
             if (!curr_selection.empty() && !curr_selection.back() &&
-                utxo.effective_value == utxo_pool.at(curr_selection.size() - 1).effective_value &&
+                utxo.GetSelectionAmount() == utxo_pool.at(curr_selection.size() - 1).GetSelectionAmount() &&
                 utxo.fee == utxo_pool.at(curr_selection.size() - 1).fee) {
                 curr_selection.push_back(false);
             } else {
                 // Inclusion branch first (Largest First Exploration)
                 curr_selection.push_back(true);
-                curr_value += utxo.effective_value;
+                curr_value += utxo.GetSelectionAmount();
                 curr_waste += utxo.fee - utxo.long_term_fee;
             }
         }
@@ -283,14 +280,14 @@ bool KnapsackSolver(const CAmount& nTargetValue, std::vector<OutputGroup>& group
             if (tryDenom == 0 && CoinJoin::IsDenominatedAmount(group.m_value)) {
                 continue; // we don't want denom values on first run
             }
-            if (group.m_value == nTargetValue) {
+            if (group.GetSelectionAmount() == nTargetValue) {
                 util::insert(setCoinsRet, group.m_outputs);
                 nValueRet += group.m_value;
                 return true;
-            } else if (group.m_value < nTargetValue + nMinChange) {
+            } else if (group.GetSelectionAmount() < nTargetValue + nMinChange) {
                 applicable_groups.push_back(group);
-                nTotalLower += group.m_value;
-            } else if (!lowest_larger || group.m_value < lowest_larger->m_value) {
+                nTotalLower += group.GetSelectionAmount();
+            } else if (!lowest_larger || group.GetSelectionAmount() < lowest_larger->GetSelectionAmount()) {
                 lowest_larger = group;
             }
         }
@@ -336,7 +333,7 @@ bool KnapsackSolver(const CAmount& nTargetValue, std::vector<OutputGroup>& group
     // If we have a bigger coin and (either the stochastic approximation didn't find a good solution,
     //                                   or the next bigger coin is closer), return the bigger coin
     if (lowest_larger &&
-        ((nBest != nTargetValue && nBest < nTargetValue + nMinChange) || lowest_larger->m_value <= nBest)) {
+        ((nBest != nTargetValue && nBest < nTargetValue + nMinChange) || lowest_larger->GetSelectionAmount() <= nBest)) {
         util::insert(setCoinsRet, lowest_larger->m_outputs);
         nValueRet += lowest_larger->m_value;
     } else {
@@ -400,3 +397,8 @@ bool OutputGroup::EligibleForSpending(const CoinEligibilityFilter& eligibility_f
         && m_ancestors <= eligibility_filter.max_ancestors
         && m_descendants <= eligibility_filter.max_descendants;
 }
+
+CAmount OutputGroup::GetSelectionAmount() const
+{
+    return m_subtract_fee_outputs ? m_value : effective_value;
+}

src/wallet/coinselection.h

@@ -57,6 +57,45 @@ class CInputCoin {
     }
 };
 
+/** Parameters for one iteration of Coin Selection. */
+struct CoinSelectionParams
+{
+    /** Size of a change output in bytes, determined by the output type. */
+    size_t change_output_size = 0;
+    /** Size of the input to spend a change output in virtual bytes. */
+    size_t change_spend_size = 0;
+    /** Cost of creating the change output. */
+    CAmount m_change_fee{0};
+    /** Cost of creating the change output + cost of spending the change output in the future. */
+    CAmount m_cost_of_change{0};
+    /** The fee to spend these UTXOs at the long term feerate. */
+    CFeeRate m_effective_feerate;
+    /** The feerate estimate used to estimate an upper bound on what should be sufficient to spend
+     * the change output sometime in the future. */
+    CFeeRate m_long_term_feerate;
+    /** If the cost to spend a change output at the discard feerate exceeds its value, drop it to fees. */
+    CFeeRate m_discard_feerate;
+    size_t tx_noinputs_size = 0;
+    /** Indicate that we are subtracting the fee from outputs */
+    bool m_subtract_fee_outputs = false;
+    /** When true, always spend all (up to OUTPUT_GROUP_MAX_ENTRIES) or none of the outputs
+     * associated with the same address. This helps reduce privacy leaks resulting from address
+     * reuse. Dust outputs are not eligible to be added to output groups and thus not considered. */
+    bool m_avoid_partial_spends = false;
+
+    CoinSelectionParams(size_t change_output_size, size_t change_spend_size, CFeeRate effective_feerate,
+                        CFeeRate long_term_feerate, CFeeRate discard_feerate, size_t tx_noinputs_size, bool avoid_partial) :
+        change_output_size(change_output_size),
+        change_spend_size(change_spend_size),
+        m_effective_feerate(effective_feerate),
+        m_long_term_feerate(long_term_feerate),
+        m_discard_feerate(discard_feerate),
+        tx_noinputs_size(tx_noinputs_size),
+        m_avoid_partial_spends(avoid_partial)
+    {}
+    CoinSelectionParams() {}
+};
+
 /** Parameters for filtering which OutputGroups we may use in coin selection.
  * We start by being very selective and requiring multiple confirmations and
  * then get more permissive if we cannot fund the transaction. */
@@ -109,18 +148,23 @@ struct OutputGroup
      * a lower feerate). Calculated using long term fee estimate. This is used to decide whether
      * it could be economical to create a change output. */
     CFeeRate m_long_term_feerate{0};
+    /** Indicate that we are subtracting the fee from outputs.
+     * When true, the value that is used for coin selection is the UTXO's real value rather than effective value */
+    bool m_subtract_fee_outputs{false};
 
     OutputGroup() {}
-    OutputGroup(const CFeeRate& effective_feerate, const CFeeRate& long_term_feerate) :
-        m_effective_feerate(effective_feerate),
-        m_long_term_feerate(long_term_feerate)
+    OutputGroup(const CoinSelectionParams& params) :
+        m_effective_feerate(params.m_effective_feerate),
+        m_long_term_feerate(params.m_long_term_feerate),
+        m_subtract_fee_outputs(params.m_subtract_fee_outputs)
     {}
 
     void Insert(const CInputCoin& output, int depth, bool from_me, size_t ancestors, size_t descendants, bool positive_only);
     bool EligibleForSpending(const CoinEligibilityFilter& eligibility_filter, bool isISLocked) const;
+    CAmount GetSelectionAmount() const;
 };
 
-bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& target_value, const CAmount& cost_of_change, std::set<CInputCoin>& out_set, CAmount& value_ret, CAmount not_input_fees);
+bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& selection_target, const CAmount& cost_of_change, std::set<CInputCoin>& out_set, CAmount& value_ret);
 
 // Original coin selection algorithm as a fallback
 bool KnapsackSolver(const CAmount& nTargetValue, std::vector<OutputGroup>& groups, std::set<CInputCoin>& setCoinsRet, CAmount& nValueRet, bool fFulyMixedOnly, CAmount maxTxFee);