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txgraph: Special-case singletons in chunk index (optimization)

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Pieter Wuille 2024-11-27 15:29:40 -05:00
parent df4578d2aa
commit a0becaaa9c
1 changed files with 40 additions and 12 deletions
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32
src/txgraph.cpp
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@ -263,7 +263,7 @@ private:
{
/** The Entry which is the last transaction of the chunk. */
mutable GraphIndex m_graph_index;
/** How many transactions the chunk contains. */
/** How many transactions the chunk contains (-1 = singleton tail of cluster). */
LinearizationIndex m_chunk_count;
ChunkData(GraphIndex graph_index, LinearizationIndex chunk_count) noexcept :
@ -670,7 +670,7 @@ void Cluster::Updated(TxGraphImpl& graph) noexcept
// Iterate over the chunks.
for (unsigned chunk_idx = 0; chunk_idx < chunking.NumChunksLeft(); ++chunk_idx) {
auto chunk = chunking.GetChunk(chunk_idx);
const auto chunk_count = chunk.transactions.Count();
auto chunk_count = chunk.transactions.Count();
Assume(chunk_count > 0);
// Iterate over the transactions in the linearization, which must match those in chunk.
while (true) {
@ -683,6 +683,12 @@ void Cluster::Updated(TxGraphImpl& graph) noexcept
chunk.transactions.Reset(idx);
if (chunk.transactions.None()) {
// Last transaction in the chunk.
if (chunk_count == 1 && chunk_idx + 1 == chunking.NumChunksLeft()) {
// If this is the final chunk of the cluster, and it contains just a single
// transaction (which will always be true for the very common singleton
// clusters), store the special value -1 as chunk count.
chunk_count = LinearizationIndex(-1);
}
graph.CreateChunkData(graph_idx, chunk_count);
break;
}
@ -2149,8 +2155,12 @@ void Cluster::SanityCheck(const TxGraphImpl& graph, int level) const
assert((entry.m_main_chunkindex_iterator != graph.m_main_chunkindex.end()) == is_chunk_end);
if (is_chunk_end) {
auto& chunk_data = *entry.m_main_chunkindex_iterator;
if (m_done == m_depgraph.Positions() && chunk_pos == 1) {
assert(chunk_data.m_chunk_count == LinearizationIndex(-1));
} else {
assert(chunk_data.m_chunk_count == chunk_pos);
}
}
// If this Cluster has an acceptable quality level, its chunks must be connected.
assert(m_depgraph.IsConnected(linchunking.GetChunk(0).transactions));
}
@ -2354,14 +2364,25 @@ std::optional<std::pair<std::vector<TxGraph::Ref*>, FeePerWeight>> BlockBuilderI
const auto& chunk_data = *m_cur_iter;
const auto& chunk_end_entry = m_graph->m_entries[chunk_data.m_graph_index];
auto cluster = chunk_end_entry.m_locator[0].cluster;
if (chunk_data.m_chunk_count == LinearizationIndex(-1)) {
// Special case in case just a single transaction remains, avoiding the need to
// dispatch to and dereference Cluster.
ret->first.resize(1);
Assume(chunk_end_entry.m_ref != nullptr);
ret->first[0] = chunk_end_entry.m_ref;
m_cur_cluster = nullptr;
} else {
ret->first.resize(chunk_data.m_chunk_count);
auto start_pos = chunk_end_entry.m_main_lin_index + 1 - chunk_data.m_chunk_count;
bool is_end = cluster->GetClusterRefs(*m_graph, ret->first, start_pos);
if (is_end) {
m_cur_cluster = nullptr;
// If the chunk size was 1, then the special case above should have been used.
Assume(chunk_data.m_chunk_count > 1);
} else {
Assume(cluster == m_cur_cluster);
}
}
ret->second = chunk_end_entry.m_main_chunk_feerate;
}
return ret;
@ -2427,10 +2448,17 @@ std::pair<std::vector<TxGraph::Ref*>, FeePerWeight> TxGraphImpl::GetWorstMainChu
const auto& chunk_data = *m_main_chunkindex.rbegin();
const auto& chunk_end_entry = m_entries[chunk_data.m_graph_index];
Cluster* cluster = chunk_end_entry.m_locator[0].cluster;
if (chunk_data.m_chunk_count == LinearizationIndex(-1) || chunk_data.m_chunk_count == 1) {
// Special case for singletons.
ret.first.resize(1);
Assume(chunk_end_entry.m_ref != nullptr);
ret.first[0] = chunk_end_entry.m_ref;
} else {
ret.first.resize(chunk_data.m_chunk_count);
auto start_pos = chunk_end_entry.m_main_lin_index + 1 - chunk_data.m_chunk_count;
cluster->GetClusterRefs(*this, ret.first, start_pos);
std::reverse(ret.first.begin(), ret.first.end());
}
ret.second = chunk_end_entry.m_main_chunk_feerate;
}
return ret;