From a764328c1e895d0f3f9b1a105225a4b0084fb150 Mon Sep 17 00:00:00 2001 From: Murch Date: Mon, 8 Jan 2024 13:04:29 -0500 Subject: [PATCH] opt: Skip over barren combinations of tiny UTXOs Given a lot of small amount UTXOs it is possible that the lookahead indicates sufficient funds, but any combination of them would push us beyond the current best_weight. We can estimate a lower bound for the minimal necessary weight to reach target from the maximal amount and minimal weight in the tail of the UTXO pool: if adding a number of hypothetical UTXOs of this maximum amount and minimum weight would not be able to beat `best_weight`, we can SHIFT to the omission branch, and CUT if the last selected UTXO is not heavier than the minimum weight of the remainder. --- src/wallet/coinselection.cpp | 7 +++++++ src/wallet/test/coinselector_tests.cpp | 12 ++++++------ 2 files changed, 13 insertions(+), 6 deletions(-) diff --git a/src/wallet/coinselection.cpp b/src/wallet/coinselection.cpp index e541c59c43439..63ba39cd0a0c3 100644 --- a/src/wallet/coinselection.cpp +++ b/src/wallet/coinselection.cpp @@ -337,6 +337,13 @@ util::Result CoinGrinder(std::vector& utxo_pool, c best_selection_weight = curr_weight; best_selection_amount = curr_amount; } + } else if (!best_selection.empty() && curr_weight + min_tail_weight[curr_tail] * ((selection_target + change_target - curr_amount) / utxo_pool[curr_tail].GetSelectionAmount()) > best_selection_weight) { + // Compare minimal tail weight and last selected amount with the amount missing to gauge whether a better weight is still possible. + if (utxo_pool[curr_tail].m_weight <= min_tail_weight[curr_tail]) { + should_cut = true; + } else { + should_shift = true; + } } if (curr_try >= TOTAL_TRIES) { diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp index ac7196f57848d..dae64826076e3 100644 --- a/src/wallet/test/coinselector_tests.cpp +++ b/src/wallet/test/coinselector_tests.cpp @@ -1111,7 +1111,7 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests) // 4) Test that two less valuable UTXOs with a combined lower weight are preferred over a more valuable heavier UTXO // 5) Test finding a solution in a UTXO pool with mixed weights // 6) Test that the lightest solution among many clones is found - // 7) Lots of tiny UTXOs of different amounts quickly exhausts the search attempts + // 7) Test that lots of tiny UTXOs can be skipped if they are too heavy while there are enough funds in lookahead FastRandomContext rand; CoinSelectionParams dummy_params{ // Only used to provide the 'avoid_partial' flag. @@ -1180,7 +1180,7 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests) }); BOOST_CHECK(res); // If this takes more attempts, the implementation has regressed - size_t expected_attempts = 184; + size_t expected_attempts = 37; BOOST_CHECK_MESSAGE(res->GetSelectionsEvaluated() == expected_attempts, strprintf("Expected %i attempts, but got %i", expected_attempts, res->GetSelectionsEvaluated())); } @@ -1227,7 +1227,7 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests) }); BOOST_CHECK(res); // If this takes more attempts, the implementation has regressed - size_t expected_attempts = 218; + size_t expected_attempts = 182; BOOST_CHECK_MESSAGE(res->GetSelectionsEvaluated() == expected_attempts, strprintf("Expected %i attempts, but got %i", expected_attempts, res->GetSelectionsEvaluated())); } @@ -1273,7 +1273,7 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests) { // ################################################################################################################# - // 7) Lots of tiny UTXOs of different amounts quickly exhausts the search attempts + // 7) Test that lots of tiny UTXOs can be skipped if they are too heavy while there are enough funds in lookahead // ################################################################################################################# SelectionResult expected_result(CAmount(0), SelectionAlgorithm::CG); CAmount target = 1.9L * COIN; @@ -1290,11 +1290,11 @@ BOOST_AUTO_TEST_CASE(coin_grinder_tests) return available_coins; }); expected_result.Clear(); - add_coin(1.8 * COIN, 1, expected_result); + add_coin(1 * COIN, 1, expected_result); add_coin(1 * COIN, 2, expected_result); BOOST_CHECK(EquivalentResult(expected_result, *res)); // If this takes more attempts, the implementation has regressed - size_t expected_attempts = 100'000; + size_t expected_attempts = 7; BOOST_CHECK_MESSAGE(res->GetSelectionsEvaluated() == expected_attempts, strprintf("Expected %i attempts, but got %i", expected_attempts, res->GetSelectionsEvaluated())); } }