phantom/bitcoin
1
0
Fork 0
mirror of https://github.com/bitcoin/bitcoin.git synced 2025-04-29 06:49:38 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

txgraph: compare sequence numbers instead of Cluster* (bugfix)

Browse source 
This makes fuzz testing more deterministic, by avoiding the (arbitrary) pointer
value ordering in comparing transactions.
This commit is contained in:
Pieter Wuille 2025-04-01 14:05:56 -04:00
parent b2bb27f40c
commit c72c8d5d45
2 changed files with 61 additions and 26 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
src/test/fuzz/txgraph.cpp
View file

@ -206,11 +206,14 @@ struct SimTxGraph
ret.push_back(ptr);
}
}
// Deduplicate.
std::sort(ret.begin(), ret.end());
ret.erase(std::unique(ret.begin(), ret.end()), ret.end());
// Replace input.
arg = std::move(ret);
// Construct deduplicated version in input (do not use std::sort/std::unique for
// deduplication as it'd rely on non-deterministic pointer comparison).
arg.clear();
for (auto ptr : ret) {
if (std::find(arg.begin(), arg.end(), ptr) == arg.end()) {
arg.push_back(ptr);
}
}
}
};

74
src/txgraph.cpp
View file

@ -70,12 +70,16 @@ class Cluster
ClusterSetIndex m_setindex{ClusterSetIndex(-1)};
/** Which level this Cluster is at in the graph (-1=not inserted, 0=main, 1=staging). */
int m_level{-1};
/** Sequence number for this Cluster (for tie-breaking comparison between equal-chunk-feerate
transactions in distinct clusters). */
uint64_t m_sequence;
public:
Cluster() noexcept = delete;
/** Construct an empty Cluster. */
Cluster() noexcept = default;
explicit Cluster(uint64_t sequence) noexcept;
/** Construct a singleton Cluster. */
explicit Cluster(TxGraphImpl& graph, const FeePerWeight& feerate, GraphIndex graph_index) noexcept;
explicit Cluster(uint64_t sequence, TxGraphImpl& graph, const FeePerWeight& feerate, GraphIndex graph_index) noexcept;
// Cannot move or copy (would invalidate Cluster* in Locator and ClusterSet). */
Cluster(const Cluster&) = delete;
@ -157,6 +161,7 @@ public:
void SanityCheck(const TxGraphImpl& graph, int level) const;
};
/** The transaction graph, including staged changes.
*
* The overall design of the data structure consists of 3 interlinked representations:
@ -244,6 +249,8 @@ private:
ClusterSet m_main_clusterset;
/** The staging ClusterSet, if any. */
std::optional<ClusterSet> m_staging_clusterset;
/** Next sequence number to assign to created Clusters. */
uint64_t m_next_sequence_counter{0};
/** A Locator that describes whether, where, and in which Cluster an Entry appears.
* Every Entry has MAX_LEVELS locators, as it may appear in one Cluster per level.
@ -315,6 +322,18 @@ private:
/** Set of Entries which have no linked Ref anymore. */
std::vector<GraphIndex> m_unlinked;
/** Compare two Cluster* by their m_sequence value (while supporting nullptr). */
static std::strong_ordering CompareClusters(Cluster* a, Cluster* b) noexcept
{
// The nullptr pointer compares before everything else.
if (a == nullptr || b == nullptr) {
return (a != nullptr) <=> (b != nullptr);
}
// If neither pointer is nullptr, compare the Clusters' sequence numbers.
Assume(a == b || a->m_sequence != b->m_sequence);
return a->m_sequence <=> b->m_sequence;
}
public:
/** Construct a new TxGraphImpl with the specified maximum cluster count. */
explicit TxGraphImpl(DepGraphIndex max_cluster_count) noexcept :
@ -569,7 +588,7 @@ std::vector<Cluster*> TxGraphImpl::GetConflicts() const noexcept
}
}
// Deduplicate the result (the same Cluster may appear multiple times).
std::sort(ret.begin(), ret.end());
std::sort(ret.begin(), ret.end(), [](Cluster* a, Cluster* b) noexcept { return CompareClusters(a, b) < 0; });
ret.erase(std::unique(ret.begin(), ret.end()), ret.end());
return ret;
}
@ -577,7 +596,7 @@ std::vector<Cluster*> TxGraphImpl::GetConflicts() const noexcept
Cluster* Cluster::CopyToStaging(TxGraphImpl& graph) const noexcept
{
// Construct an empty Cluster.
auto ret = std::make_unique<Cluster>();
auto ret = std::make_unique<Cluster>(graph.m_next_sequence_counter++);
auto ptr = ret.get();
// Copy depgraph, mapping, and linearization/
ptr->m_depgraph = m_depgraph;
@ -710,7 +729,7 @@ bool Cluster::Split(TxGraphImpl& graph) noexcept
}
first = false;
// Construct a new Cluster to hold the found component.
auto new_cluster = std::make_unique<Cluster>();
auto new_cluster = std::make_unique<Cluster>(graph.m_next_sequence_counter++);
new_clusters.push_back(new_cluster.get());
// Remember that all the component's transactions go to this new Cluster. The positions
// will be determined below, so use -1 for now.
@ -956,9 +975,11 @@ void TxGraphImpl::ApplyRemovals(int up_to_level) noexcept
if (cluster != nullptr) PullIn(cluster);
}
}
// Group the set of to-be-removed entries by Cluster*.
// Group the set of to-be-removed entries by Cluster::m_sequence.
std::sort(to_remove.begin(), to_remove.end(), [&](GraphIndex a, GraphIndex b) noexcept {
return std::less{}(m_entries[a].m_locator[level].cluster, m_entries[b].m_locator[level].cluster);
Cluster* cluster_a = m_entries[a].m_locator[level].cluster;
Cluster* cluster_b = m_entries[b].m_locator[level].cluster;
return CompareClusters(cluster_a, cluster_b) < 0;
});
// Process per Cluster.
std::span to_remove_span{to_remove};
@ -1103,16 +1124,16 @@ void TxGraphImpl::GroupClusters(int level) noexcept
}
// Sort and deduplicate an_clusters, so we end up with a sorted list of all involved Clusters
// to which dependencies apply.
std::sort(an_clusters.begin(), an_clusters.end());
std::sort(an_clusters.begin(), an_clusters.end(), [](auto& a, auto& b) noexcept { return CompareClusters(a.first, b.first) < 0; });
an_clusters.erase(std::unique(an_clusters.begin(), an_clusters.end()), an_clusters.end());
// Sort the dependencies by child Cluster.
// Sort the dependencies by child Cluster::m_sequence.
std::sort(clusterset.m_deps_to_add.begin(), clusterset.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 = FindCluster(a_chl, level);
auto b_chl_cluster = FindCluster(b_chl, level);
return std::less{}(a_chl_cluster, b_chl_cluster);
return CompareClusters(a_chl_cluster, b_chl_cluster) < 0;
});
// Run the union-find algorithm to to find partitions of the input Clusters which need to be
@ -1132,13 +1153,13 @@ void TxGraphImpl::GroupClusters(int level) noexcept
* tree for this partition. */
unsigned rank;
};
/** Information about each input Cluster. Sorted by Cluster* pointer. */
/** Information about each input Cluster. Sorted by Cluster::m_sequence. */
std::vector<PartitionData> partition_data;
/** Given a Cluster, find its corresponding PartitionData. */
auto locate_fn = [&](Cluster* arg) noexcept -> PartitionData* {
auto it = std::lower_bound(partition_data.begin(), partition_data.end(), arg,
[](auto& a, Cluster* ptr) noexcept { return a.cluster < ptr; });
[](auto& a, Cluster* ptr) noexcept { return CompareClusters(a.cluster, ptr) < 0; });
Assume(it != partition_data.end());
Assume(it->cluster == arg);
return &*it;
@ -1219,7 +1240,7 @@ void TxGraphImpl::GroupClusters(int level) noexcept
while (deps_it != clusterset.m_deps_to_add.end()) {
auto [par, chl] = *deps_it;
auto chl_cluster = FindCluster(chl, level);
if (std::greater{}(chl_cluster, data.cluster)) break;
if (CompareClusters(chl_cluster, data.cluster) > 0) 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) {
@ -1234,8 +1255,8 @@ void TxGraphImpl::GroupClusters(int level) noexcept
// Sort both an_clusters and an_deps by representative of the partition they are in, grouping
// all those applying to the same partition together.
std::sort(an_deps.begin(), an_deps.end(), [](auto& a, auto& b) noexcept { return a.second < b.second; });
std::sort(an_clusters.begin(), an_clusters.end(), [](auto& a, auto& b) noexcept { return a.second < b.second; });
std::sort(an_deps.begin(), an_deps.end(), [](auto& a, auto& b) noexcept { return CompareClusters(a.second, b.second) < 0; });
std::sort(an_clusters.begin(), an_clusters.end(), [](auto& a, auto& b) noexcept { return CompareClusters(a.second, b.second) < 0; });
// Translate the resulting cluster groups to the m_group_data structure, and the dependencies
// back to m_deps_to_add.
@ -1390,7 +1411,10 @@ void TxGraphImpl::MakeAllAcceptable(int level) noexcept
}
}
Cluster::Cluster(TxGraphImpl& graph, const FeePerWeight& feerate, GraphIndex graph_index) noexcept
Cluster::Cluster(uint64_t sequence) noexcept : m_sequence{sequence} {}
Cluster::Cluster(uint64_t sequence, TxGraphImpl& graph, const FeePerWeight& feerate, GraphIndex graph_index) noexcept :
m_sequence{sequence}
{
// Create a new transaction in the DepGraph, and remember its position in m_mapping.
auto cluster_idx = m_depgraph.AddTransaction(feerate);
@ -1410,7 +1434,7 @@ TxGraph::Ref TxGraphImpl::AddTransaction(const FeePerWeight& feerate) noexcept
GetRefGraph(ret) = this;
GetRefIndex(ret) = idx;
// Construct a new singleton Cluster (which is necessarily optimally linearized).
auto cluster = std::make_unique<Cluster>(*this, feerate, idx);
auto cluster = std::make_unique<Cluster>(m_next_sequence_counter++, *this, feerate, idx);
auto cluster_ptr = cluster.get();
int level = GetTopLevel();
auto& clusterset = GetClusterSet(level);
@ -1606,7 +1630,7 @@ std::vector<TxGraph::Ref*> TxGraphImpl::GetAncestorsUnion(std::span<const Ref* c
matches.emplace_back(cluster, m_entries[GetRefIndex(*arg)].m_locator[cluster->m_level].index);
}
// Group by Cluster.
std::sort(matches.begin(), matches.end(), [](auto& a, auto& b) noexcept { return std::less{}(a.first, b.first); });
std::sort(matches.begin(), matches.end(), [](auto& a, auto& b) noexcept { return CompareClusters(a.first, b.first) < 0; });
// Dispatch to the Clusters.
std::span match_span(matches);
std::vector<TxGraph::Ref*> ret;
@ -1639,7 +1663,7 @@ std::vector<TxGraph::Ref*> TxGraphImpl::GetDescendantsUnion(std::span<const Ref*
matches.emplace_back(cluster, m_entries[GetRefIndex(*arg)].m_locator[cluster->m_level].index);
}
// Group by Cluster.
std::sort(matches.begin(), matches.end(), [](auto& a, auto& b) noexcept { return std::less{}(a.first, b.first); });
std::sort(matches.begin(), matches.end(), [](auto& a, auto& b) noexcept { return CompareClusters(a.first, b.first) < 0; });
// Dispatch to the Clusters.
std::span match_span(matches);
std::vector<TxGraph::Ref*> ret;
@ -1867,7 +1891,9 @@ std::strong_ordering TxGraphImpl::CompareMainOrder(const Ref& a, const Ref& b) n
if (feerate_cmp < 0) return std::strong_ordering::less;
if (feerate_cmp > 0) return std::strong_ordering::greater;
// Compare Cluster* as tie-break for equal chunk feerates.
if (locator_a.cluster != locator_b.cluster) return locator_a.cluster <=> locator_b.cluster;
if (locator_a.cluster != locator_b.cluster) {
return CompareClusters(locator_a.cluster, locator_b.cluster);
}
// As final tie-break, compare position within cluster linearization.
return entry_a.m_main_lin_index <=> entry_b.m_main_lin_index;
}
@ -1889,7 +1915,7 @@ TxGraph::GraphIndex TxGraphImpl::CountDistinctClusters(std::span<const Ref* cons
if (cluster != nullptr) clusters.push_back(cluster);
}
// Count the number of distinct elements in clusters.
std::sort(clusters.begin(), clusters.end());
std::sort(clusters.begin(), clusters.end(), [](Cluster* a, Cluster* b) noexcept { return CompareClusters(a, b) < 0; });
Cluster* last{nullptr};
GraphIndex ret{0};
for (Cluster* cluster : clusters) {
@ -1951,6 +1977,8 @@ void TxGraphImpl::SanityCheck() const
std::set<const Cluster*> expected_clusters[MAX_LEVELS];
/** Which GraphIndexes ought to occur in ClusterSet::m_removed, based on m_entries. */
std::set<GraphIndex> expected_removed[MAX_LEVELS];
/** Which Cluster::m_sequence values have been encountered. */
std::set<uint64_t> sequences;
/** Whether compaction is possible in the current state. */
bool compact_possible{true};
@ -2004,6 +2032,10 @@ void TxGraphImpl::SanityCheck() const
// ... for all clusters in them ...
for (ClusterSetIndex setindex = 0; setindex < quality_clusters.size(); ++setindex) {
const auto& cluster = *quality_clusters[setindex];
// Check the sequence number.
assert(cluster.m_sequence < m_next_sequence_counter);
assert(sequences.count(cluster.m_sequence) == 0);
sequences.insert(cluster.m_sequence);
// Remember we saw this Cluster (only if it is non-empty; empty Clusters aren't
// expected to be referenced by the Entry vector).
if (cluster.GetTxCount() != 0) {