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clusterlin: only start/use search when enough iterations left

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This commit is contained in:
Pieter Wuille
2024-07-25 00:13:11 -04:00
parent bd044356ed
commit 9ad2fe7e69
2 changed files with 47 additions and 12 deletions
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40
src/cluster_linearize.h
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@@ -536,6 +536,12 @@ public:
return m_todo.None();
}
/** Count the number of remaining unlinearized transactions. */
ClusterIndex NumRemaining() const noexcept
{
return m_todo.Count();
}
/** Find the best (highest-feerate, smallest among those in case of a tie) ancestor set
* among the remaining transactions. Requires !AllDone().
*
@@ -960,10 +966,20 @@ std::pair<std::vector<ClusterIndex>, bool> Linearize(const DepGraph<SetType>& de
std::vector<ClusterIndex> linearization;
AncestorCandidateFinder anc_finder(depgraph);
SearchCandidateFinder src_finder(depgraph, rng_seed);
std::optional<SearchCandidateFinder<SetType>> src_finder;
linearization.reserve(depgraph.TxCount());
bool optimal = true;
// Treat the initialization of SearchCandidateFinder as taking N^2/64 (rounded up) iterations
// (largely due to the cost of constructing the internal sorted-by-feerate DepGraph inside
// SearchCandidateFinder), a rough approximation based on benchmark. If we don't have that
// many, don't start it.
uint64_t start_iterations = (uint64_t{depgraph.TxCount()} * depgraph.TxCount() + 63) / 64;
if (iterations_left > start_iterations) {
iterations_left -= start_iterations;
src_finder.emplace(depgraph, rng_seed);
}
/** Chunking of what remains of the old linearization. */
LinearizationChunking old_chunking(depgraph, old_linearization);
@@ -976,12 +992,22 @@ std::pair<std::vector<ClusterIndex>, bool> Linearize(const DepGraph<SetType>& de
auto best = anc_finder.FindCandidateSet();
if (!best_prefix.feerate.IsEmpty() && best_prefix.feerate >= best.feerate) best = best_prefix;
// Invoke bounded search to update best, with up to half of our remaining iterations as
// limit.
uint64_t max_iterations_now = (iterations_left + 1) / 2;
uint64_t iterations_done_now = 0;
std::tie(best, iterations_done_now) = src_finder.FindCandidateSet(max_iterations_now, best);
iterations_left -= iterations_done_now;
uint64_t max_iterations_now = 0;
if (src_finder) {
// Treat the invocation of SearchCandidateFinder::FindCandidateSet() as costing N/4
// up-front (rounded up) iterations (largely due to the cost of connected-component
// splitting), a rough approximation based on benchmarks.
uint64_t base_iterations = (anc_finder.NumRemaining() + 3) / 4;
if (iterations_left > base_iterations) {
// Invoke bounded search to update best, with up to half of our remaining
// iterations as limit.
iterations_left -= base_iterations;
max_iterations_now = (iterations_left + 1) / 2;
std::tie(best, iterations_done_now) = src_finder->FindCandidateSet(max_iterations_now, best);
iterations_left -= iterations_done_now;
}
}
if (iterations_done_now == max_iterations_now) {
optimal = false;
@@ -999,7 +1025,7 @@ std::pair<std::vector<ClusterIndex>, bool> Linearize(const DepGraph<SetType>& de
// Update state to reflect best is no longer to be linearized.
anc_finder.MarkDone(best.transactions);
if (anc_finder.AllDone()) break;
src_finder.MarkDone(best.transactions);
if (src_finder) src_finder->MarkDone(best.transactions);
if (old_chunking.NumChunksLeft() > 0) {
old_chunking.MarkDone(best.transactions);
}