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wallet: accurate SelectionResult::m_target

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SelectionResult::m_target should be equal to actual selection target.
Selection target is the sum of all recipient amounts plus non input fees.
So we need to remove change_fee from the m_target. It's safe because change
target is always greater than the change fee, so we can always cover fees
if change output is created.
This commit is contained in:
S3RK 2022-07-06 08:51:22 +02:00
parent c8cf08ea74
commit 06f558e4e2
2 changed files with 10 additions and 16 deletions
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6
src/wallet/coinselection.cpp
View File

@ -166,6 +166,12 @@ std::optional<SelectionResult> SelectCoinsSRD(const std::vector<OutputGroup>& ut
{
SelectionResult result(target_value, SelectionAlgorithm::SRD);
// Include change for SRD as we want to avoid making really small change if the selection just
// barely meets the target. Just use the lower bound change target instead of the randomly
// generated one, since SRD will result in a random change amount anyway; avoid making the
// target needlessly large.
target_value += CHANGE_LOWER;
std::vector<size_t> indexes;
indexes.resize(utxo_pool.size());
std::iota(indexes.begin(), indexes.end(), 0);

20
src/wallet/spend.cpp
View File

@ -489,31 +489,19 @@ std::optional<SelectionResult> ChooseSelectionResult(const CWallet& wallet, cons
// Vector of results. We will choose the best one based on waste.
std::vector<SelectionResult> results;
// Note that unlike KnapsackSolver, we do not include the fee for creating a change output as BnB will not create a change output.
std::vector<OutputGroup> positive_groups = GroupOutputs(wallet, available_coins, coin_selection_params, eligibility_filter, true /* positive_only */);
std::vector<OutputGroup> positive_groups = GroupOutputs(wallet, available_coins, coin_selection_params, eligibility_filter, /*positive_only=*/true);
if (auto bnb_result{SelectCoinsBnB(positive_groups, nTargetValue, coin_selection_params.m_cost_of_change)}) {
results.push_back(*bnb_result);
}
// The knapsack solver has some legacy behavior where it will spend dust outputs. We retain this behavior, so don't filter for positive only here.
std::vector<OutputGroup> all_groups = GroupOutputs(wallet, available_coins, coin_selection_params, eligibility_filter, false /* positive_only */);
CAmount target_with_change = nTargetValue;
// While nTargetValue includes the transaction fees for non-input things, it does not include the fee for creating a change output.
// So we need to include that for KnapsackSolver and SRD as well, as we are expecting to create a change output.
if (!coin_selection_params.m_subtract_fee_outputs) {
target_with_change += coin_selection_params.m_change_fee;
}
if (auto knapsack_result{KnapsackSolver(all_groups, target_with_change, coin_selection_params.m_min_change_target, coin_selection_params.rng_fast)}) {
std::vector<OutputGroup> all_groups = GroupOutputs(wallet, available_coins, coin_selection_params, eligibility_filter, /*positive_only=*/false);
if (auto knapsack_result{KnapsackSolver(all_groups, nTargetValue, coin_selection_params.m_min_change_target, coin_selection_params.rng_fast)}) {
knapsack_result->ComputeAndSetWaste(coin_selection_params.m_cost_of_change);
results.push_back(*knapsack_result);
}
// Include change for SRD as we want to avoid making really small change if the selection just
// barely meets the target. Just use the lower bound change target instead of the randomly
// generated one, since SRD will result in a random change amount anyway; avoid making the
// target needlessly large.
const CAmount srd_target = target_with_change + CHANGE_LOWER;
if (auto srd_result{SelectCoinsSRD(positive_groups, srd_target, coin_selection_params.rng_fast)}) {
if (auto srd_result{SelectCoinsSRD(positive_groups, nTargetValue, coin_selection_params.rng_fast)}) {
srd_result->ComputeAndSetWaste(coin_selection_params.m_cost_of_change);
results.push_back(*srd_result);
}