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wallet: calculate and store min_viable_change

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S3RK
2022-07-06 09:00:57 +02:00
parent e3210a7225
commit 72cad28da0
2 changed files with 11 additions and 0 deletions
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4
src/wallet/coinselection.h
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@@ -123,6 +123,10 @@ struct CoinSelectionParams {
/** Mininmum change to target in Knapsack solver: select coins to cover the payment and /** Mininmum change to target in Knapsack solver: select coins to cover the payment and
* at least this value of change. */ * at least this value of change. */
CAmount m_min_change_target{0}; CAmount m_min_change_target{0};
/** Minimum amount for creating a change output.
* If change budget is smaller than min_change then we forgo creation of change output.
*/
CAmount min_viable_change{0};
/** Cost of creating the change output. */ /** Cost of creating the change output. */
CAmount m_change_fee{0}; CAmount m_change_fee{0};
/** Cost of creating the change output + cost of spending the change output in the future. */ /** Cost of creating the change output + cost of spending the change output in the future. */

7
src/wallet/spend.cpp
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@@ -855,6 +855,13 @@ static util::Result<CreatedTransactionResult> CreateTransactionInternal(
coin_selection_params.m_min_change_target = GenerateChangeTarget(std::floor(recipients_sum / vecSend.size()), coin_selection_params.m_change_fee, rng_fast); coin_selection_params.m_min_change_target = GenerateChangeTarget(std::floor(recipients_sum / vecSend.size()), coin_selection_params.m_change_fee, rng_fast);
// The smallest change amount should be:
// 1. at least equal to dust threshold
// 2. at least 1 sat greater than fees to spend it at m_discard_feerate
const auto dust = GetDustThreshold(change_prototype_txout, coin_selection_params.m_discard_feerate);
const auto change_spend_fee = coin_selection_params.m_discard_feerate.GetFee(coin_selection_params.change_spend_size);
coin_selection_params.min_viable_change = std::max(change_spend_fee + 1, dust);
// vouts to the payees // vouts to the payees
if (!coin_selection_params.m_subtract_fee_outputs) { if (!coin_selection_params.m_subtract_fee_outputs) {
coin_selection_params.tx_noinputs_size = 10; // Static vsize overhead + outputs vsize. 4 nVersion, 4 nLocktime, 1 input count, 1 witness overhead (dummy, flag, stack size) coin_selection_params.tx_noinputs_size = 10; // Static vsize overhead + outputs vsize. 4 nVersion, 4 nLocktime, 1 input count, 1 witness overhead (dummy, flag, stack size)