diff options
| -rw-r--r-- | src/wallet/coinselection.cpp | 27 | ||||
| -rw-r--r-- | src/wallet/coinselection.h | 15 |
2 files changed, 42 insertions, 0 deletions
diff --git a/src/wallet/coinselection.cpp b/src/wallet/coinselection.cpp index 25b1ee07e4..1699424657 100644 --- a/src/wallet/coinselection.cpp +++ b/src/wallet/coinselection.cpp @@ -341,3 +341,30 @@ CAmount OutputGroup::GetSelectionAmount() const { return m_subtract_fee_outputs ? m_value : effective_value; } + +CAmount GetSelectionWaste(const std::set<CInputCoin>& inputs, CAmount change_cost, CAmount target, bool use_effective_value) +{ + // This function should not be called with empty inputs as that would mean the selection failed + assert(!inputs.empty()); + + // Always consider the cost of spending an input now vs in the future. + CAmount waste = 0; + CAmount selected_effective_value = 0; + for (const CInputCoin& coin : inputs) { + waste += coin.m_fee - coin.m_long_term_fee; + selected_effective_value += use_effective_value ? coin.effective_value : coin.txout.nValue; + } + + if (change_cost) { + // Consider the cost of making change and spending it in the future + // If we aren't making change, the caller should've set change_cost to 0 + assert(change_cost > 0); + waste += change_cost; + } else { + // When we are not making change (change_cost == 0), consider the excess we are throwing away to fees + assert(selected_effective_value >= target); + waste += selected_effective_value - target; + } + + return waste; +} diff --git a/src/wallet/coinselection.h b/src/wallet/coinselection.h index 7a3fb82139..35617d455b 100644 --- a/src/wallet/coinselection.h +++ b/src/wallet/coinselection.h @@ -166,6 +166,21 @@ struct OutputGroup CAmount GetSelectionAmount() const; }; +/** Compute the waste for this result given the cost of change + * and the opportunity cost of spending these inputs now vs in the future. + * If change exists, waste = change_cost + inputs * (effective_feerate - long_term_feerate) + * If no change, waste = excess + inputs * (effective_feerate - long_term_feerate) + * where excess = selected_effective_value - target + * change_cost = effective_feerate * change_output_size + long_term_feerate * change_spend_size + * + * @param[in] inputs The selected inputs + * @param[in] change_cost The cost of creating change and spending it in the future. Only used if there is change. Must be 0 if there is no change. + * @param[in] target The amount targeted by the coin selection algorithm. + * @param[in] use_effective_value Whether to use the input's effective value (when true) or the real value (when false). + * @return The waste + */ +[[nodiscard]] CAmount GetSelectionWaste(const std::set<CInputCoin>& inputs, CAmount change_cost, CAmount target, bool use_effective_value = true); + 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 |