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txgraph: Avoid representative lookup for each dependency (optimization)

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The m_deps_to_add vector is sorted by child Cluster*, which matches the
order of an_clusters. This means we can walk through m_deps_to_add while
doing the representative lookups for an_clusters, and reuse them.
This commit is contained in:
Pieter Wuille 2025-01-22 14:53:32 -05:00
parent 64f69ec8c3
commit 1171953ac6
1 changed files with 25 additions and 12 deletions
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33
src/txgraph.cpp
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@ -734,6 +734,15 @@ void TxGraphImpl::GroupClusters() noexcept
std::sort(an_clusters.begin(), an_clusters.end());
an_clusters.erase(std::unique(an_clusters.begin(), an_clusters.end()), an_clusters.end());
// Sort the dependencies by child Cluster.
std::sort(m_deps_to_add.begin(), m_deps_to_add.end(), [&](auto& a, auto& b) noexcept {
auto [_a_par, a_chl] = a;
auto [_b_par, b_chl] = b;
auto a_chl_cluster = m_entries[a_chl].m_locator.cluster;
auto b_chl_cluster = m_entries[b_chl].m_locator.cluster;
return std::less{}(a_chl_cluster, b_chl_cluster);
});
// Run the union-find algorithm to to find partitions of the input Clusters which need to be
// grouped together. See https://en.wikipedia.org/wiki/Disjoint-set_data_structure.
{
@ -813,6 +822,8 @@ void TxGraphImpl::GroupClusters() noexcept
// Populate the an_clusters and an_deps data structures with the list of input Clusters,
// and the input dependencies, annotated with the representative of the Cluster partition
// it applies to.
an_deps.reserve(m_deps_to_add.size());
auto deps_it = m_deps_to_add.begin();
for (size_t i = 0; i < partition_data.size(); ++i) {
auto& data = partition_data[i];
// Find the representative of the partition Cluster i is in, and store it with the
@ -820,18 +831,20 @@ void TxGraphImpl::GroupClusters() noexcept
auto rep = find_root_fn(&data)->cluster;
Assume(an_clusters[i].second == nullptr);
an_clusters[i].second = rep;
}
an_deps.reserve(m_deps_to_add.size());
for (auto [par, chl] : m_deps_to_add) {
// Find all dependencies whose child Cluster is Cluster i, and annotate them with rep.
while (deps_it != m_deps_to_add.end()) {
auto [par, chl] = *deps_it;
auto chl_cluster = m_entries[chl].m_locator.cluster;
if (std::greater{}(chl_cluster, data.cluster)) break;
// Skip dependencies that apply to earlier Clusters (those necessary are for
// deleted transactions, as otherwise we'd have processed them already).
if (chl_cluster == data.cluster) {
auto par_cluster = m_entries[par].m_locator.cluster;
// Nothing to do if either parent or child transaction is removed already.
if (par_cluster == nullptr || chl_cluster == nullptr) continue;
// Find the representative of the partition which this dependency's child is in (which
// should be the same as the one for the parent).
auto rep = find_root_fn(locate_fn(chl_cluster))->cluster;
// Create an_deps entry.
an_deps.emplace_back(std::pair{par, chl}, rep);
// Also filter out dependencies applying to a removed parent.
if (par_cluster != nullptr) an_deps.emplace_back(*deps_it, rep);
}
++deps_it;
}
}
}