Files
bitcoin/src/test/fuzz/cluster_linearize.cpp
Pieter Wuille 75bdb925f4 clusterlin: drop support for improvable chunking (simplification)
With MergeLinearizations() gone and the LIMO-based Linearize() replaced by SFL, we do not
need a class (LinearizationChunking) that can maintain an incrementally-improving chunk
set anymore.

Replace it with a function (ChunkLinearizationInfo) that just computes the chunks as
SetInfos once, and returns them as a vector. This simplifies several call sites too.
2025-12-18 16:01:31 -05:00

1243 lines
50 KiB
C++

// Copyright (c) The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <cluster_linearize.h>
#include <random.h>
#include <serialize.h>
#include <streams.h>
#include <test/fuzz/FuzzedDataProvider.h>
#include <test/fuzz/fuzz.h>
#include <test/util/cluster_linearize.h>
#include <util/bitset.h>
#include <util/feefrac.h>
#include <algorithm>
#include <cstdint>
#include <utility>
#include <vector>
/*
* The tests in this file primarily cover the candidate finder classes and linearization algorithms.
*
* <----: An implementation (at the start of the line --) is tested in the test marked with *,
* possibly by comparison with other implementations (at the end of the line ->).
* <<---: The right side is implemented using the left side.
*
* +---------------------+ +-----------+
* | SpanningForestState | <<-------------------- | Linearize |
* +---------------------+ +-----------+
* | |
* | | ^^ PRODUCTION CODE
* | | ||
* ==============================================================================================
* | | ||
* |-clusterlin_sfl* | vv TEST CODE
* | |
* \------------------------------------\ |-clusterlin_linearize*
* | |
* v v
* +-----------------------+ +-----------------+
* | SimpleCandidateFinder | <<-------------------| SimpleLinearize |
* +-----------------------+ +-----------------+
* | |
* |-clusterlin_simple_finder* |-clusterlin_simple_linearize*
* v v
* +---------------------------+ +---------------------+
* | ExhaustiveCandidateFinder | | ExhaustiveLinearize |
* +---------------------------+ +---------------------+
*
* More tests are included for lower-level and related functions and classes:
* - DepGraph tests:
* - clusterlin_depgraph_sim
* - clusterlin_depgraph_serialization
* - clusterlin_components
* - ChunkLinearization and ChunkLinearizationInfo tests:
* - clusterlin_chunking
* - PostLinearize tests:
* - clusterlin_postlinearize
* - clusterlin_postlinearize_tree
* - clusterlin_postlinearize_moved_leaf
* - FixLinearization tests:
* - clusterlin_fix_linearization
* - MakeConnected tests (a test-only function):
* - clusterlin_make_connected
*/
using namespace cluster_linearize;
namespace {
/** A simple finder class for candidate sets (topologically-valid subsets with high feerate), only
* used by SimpleLinearize below. */
template<typename SetType>
class SimpleCandidateFinder
{
/** Internal dependency graph. */
const DepGraph<SetType>& m_depgraph;
/** Which transaction are left to include. */
SetType m_todo;
public:
/** Construct an SimpleCandidateFinder for a given graph. */
SimpleCandidateFinder(const DepGraph<SetType>& depgraph LIFETIMEBOUND) noexcept :
m_depgraph(depgraph), m_todo{depgraph.Positions()} {}
/** Remove a set of transactions from the set of to-be-linearized ones. */
void MarkDone(SetType select) noexcept { m_todo -= select; }
/** Determine whether unlinearized transactions remain. */
bool AllDone() const noexcept { return m_todo.None(); }
/** Find a candidate set using at most max_iterations iterations, and the number of iterations
* actually performed. If that number is less than max_iterations, then the result is optimal.
*
* Always returns a connected set of transactions.
*
* Complexity: O(N * M), where M is the number of connected topological subsets of the cluster.
* That number is bounded by M <= 2^(N-1).
*/
std::pair<SetInfo<SetType>, uint64_t> FindCandidateSet(uint64_t max_iterations) const noexcept
{
uint64_t iterations_left = max_iterations;
// Queue of work units. Each consists of:
// - inc: set of transactions definitely included
// - und: set of transactions that can be added to inc still
std::vector<std::pair<SetType, SetType>> queue;
// Initially we have just one queue element, with the entire graph in und.
queue.emplace_back(SetType{}, m_todo);
// Best solution so far. Initialize with the remaining ancestors of the first remaining
// transaction.
SetInfo best(m_depgraph, m_depgraph.Ancestors(m_todo.First()) & m_todo);
// Process the queue.
while (!queue.empty() && iterations_left) {
// Pop top element of the queue.
auto [inc, und] = queue.back();
queue.pop_back();
// Look for a transaction to consider adding/removing.
bool inc_none = inc.None();
for (auto split : und) {
// If inc is empty, consider any split transaction. Otherwise only consider
// transactions that share ancestry with inc so far (which means only connected
// sets will be considered).
if (inc_none || inc.Overlaps(m_depgraph.Ancestors(split))) {
--iterations_left;
// Add a queue entry with split included.
SetInfo new_inc(m_depgraph, inc | (m_todo & m_depgraph.Ancestors(split)));
queue.emplace_back(new_inc.transactions, und - new_inc.transactions);
// Add a queue entry with split excluded.
queue.emplace_back(inc, und - m_depgraph.Descendants(split));
// Update statistics to account for the candidate new_inc.
if (new_inc.feerate > best.feerate) best = new_inc;
break;
}
}
}
return {std::move(best), max_iterations - iterations_left};
}
};
/** A very simple finder class for optimal candidate sets, which tries every subset.
*
* It is even simpler than SimpleCandidateFinder, and exists just to help test the correctness of
* SimpleCandidateFinder, so that it can be used in SimpleLinearize, which is then used to test the
* correctness of Linearize.
*/
template<typename SetType>
class ExhaustiveCandidateFinder
{
/** Internal dependency graph. */
const DepGraph<SetType>& m_depgraph;
/** Which transaction are left to include. */
SetType m_todo;
public:
/** Construct an ExhaustiveCandidateFinder for a given graph. */
ExhaustiveCandidateFinder(const DepGraph<SetType>& depgraph LIFETIMEBOUND) noexcept :
m_depgraph(depgraph), m_todo{depgraph.Positions()} {}
/** Remove a set of transactions from the set of to-be-linearized ones. */
void MarkDone(SetType select) noexcept { m_todo -= select; }
/** Determine whether unlinearized transactions remain. */
bool AllDone() const noexcept { return m_todo.None(); }
/** Find the optimal remaining candidate set.
*
* Complexity: O(N * 2^N).
*/
SetInfo<SetType> FindCandidateSet() const noexcept
{
// Best solution so far.
SetInfo<SetType> best{m_todo, m_depgraph.FeeRate(m_todo)};
// The number of combinations to try.
uint64_t limit = (uint64_t{1} << m_todo.Count()) - 1;
// Try the transitive closure of every non-empty subset of m_todo.
for (uint64_t x = 1; x < limit; ++x) {
// If bit number b is set in x, then the remaining ancestors of the b'th remaining
// transaction in m_todo are included.
SetType txn;
auto x_shifted{x};
for (auto i : m_todo) {
if (x_shifted & 1) txn |= m_depgraph.Ancestors(i);
x_shifted >>= 1;
}
SetInfo cur(m_depgraph, txn & m_todo);
if (cur.feerate > best.feerate) best = cur;
}
return best;
}
};
/** A simple linearization algorithm.
*
* This matches Linearize() in interface and behavior, though with fewer optimizations, lacking
* the ability to pass in an existing linearization, and linearizing by simply finding the
* consecutive remaining highest-feerate topological subset using SimpleCandidateFinder.
*/
template<typename SetType>
std::pair<std::vector<DepGraphIndex>, bool> SimpleLinearize(const DepGraph<SetType>& depgraph, uint64_t max_iterations)
{
std::vector<DepGraphIndex> linearization;
SimpleCandidateFinder finder(depgraph);
SetType todo = depgraph.Positions();
bool optimal = true;
while (todo.Any()) {
auto [candidate, iterations_done] = finder.FindCandidateSet(max_iterations);
if (iterations_done == max_iterations) optimal = false;
depgraph.AppendTopo(linearization, candidate.transactions);
todo -= candidate.transactions;
finder.MarkDone(candidate.transactions);
max_iterations -= iterations_done;
}
return {std::move(linearization), optimal};
}
/** An even simpler linearization algorithm that tries all permutations.
*
* This roughly matches SimpleLinearize() (and Linearize) in interface and behavior, but always
* tries all topologically-valid transaction orderings, has no way to bound how much work it does,
* and always finds the optimal. With an O(n!) complexity, it should only be used for small
* clusters.
*/
template<typename SetType>
std::vector<DepGraphIndex> ExhaustiveLinearize(const DepGraph<SetType>& depgraph)
{
// The best linearization so far, and its chunking.
std::vector<DepGraphIndex> linearization;
std::vector<FeeFrac> chunking;
std::vector<DepGraphIndex> perm_linearization;
// Initialize with the lexicographically-first linearization.
for (DepGraphIndex i : depgraph.Positions()) perm_linearization.push_back(i);
// Iterate over all valid permutations.
do {
/** What prefix of perm_linearization is topological. */
DepGraphIndex topo_length{0};
TestBitSet perm_done;
while (topo_length < perm_linearization.size()) {
auto i = perm_linearization[topo_length];
perm_done.Set(i);
if (!depgraph.Ancestors(i).IsSubsetOf(perm_done)) break;
++topo_length;
}
if (topo_length == perm_linearization.size()) {
// If all of perm_linearization is topological, check if it is perhaps our best
// linearization so far.
auto perm_chunking = ChunkLinearization(depgraph, perm_linearization);
auto cmp = CompareChunks(perm_chunking, chunking);
// If the diagram is better, or if it is equal but with more chunks (because we
// prefer minimal chunks), consider this better.
if (linearization.empty() || cmp > 0 || (cmp == 0 && perm_chunking.size() > chunking.size())) {
linearization = perm_linearization;
chunking = perm_chunking;
}
} else {
// Otherwise, fast forward to the last permutation with the same non-topological
// prefix.
auto first_non_topo = perm_linearization.begin() + topo_length;
assert(std::is_sorted(first_non_topo + 1, perm_linearization.end()));
std::reverse(first_non_topo + 1, perm_linearization.end());
}
} while(std::next_permutation(perm_linearization.begin(), perm_linearization.end()));
return linearization;
}
/** Stitch connected components together in a DepGraph, guaranteeing its corresponding cluster is connected. */
template<typename BS>
void MakeConnected(DepGraph<BS>& depgraph)
{
auto todo = depgraph.Positions();
auto comp = depgraph.FindConnectedComponent(todo);
Assume(depgraph.IsConnected(comp));
todo -= comp;
while (todo.Any()) {
auto nextcomp = depgraph.FindConnectedComponent(todo);
Assume(depgraph.IsConnected(nextcomp));
depgraph.AddDependencies(BS::Singleton(comp.Last()), nextcomp.First());
todo -= nextcomp;
comp = nextcomp;
}
}
/** Given a dependency graph, and a todo set, read a topological subset of todo from reader. */
template<typename SetType>
SetType ReadTopologicalSet(const DepGraph<SetType>& depgraph, const SetType& todo, SpanReader& reader, bool non_empty)
{
// Read a bitmask from the fuzzing input. Add 1 if non_empty, so the mask is definitely not
// zero in that case.
uint64_t mask{0};
try {
reader >> VARINT(mask);
} catch(const std::ios_base::failure&) {}
if (mask != uint64_t(-1)) mask += non_empty;
SetType ret;
for (auto i : todo) {
if (!ret[i]) {
if (mask & 1) ret |= depgraph.Ancestors(i);
mask >>= 1;
}
}
ret &= todo;
// While mask starts off non-zero if non_empty is true, it is still possible that all its low
// bits are 0, and ret ends up being empty. As a last resort, use the in-todo ancestry of the
// first todo position.
if (non_empty && ret.None()) {
Assume(todo.Any());
ret = depgraph.Ancestors(todo.First()) & todo;
Assume(ret.Any());
}
return ret;
}
/** Given a dependency graph, construct any valid linearization for it, reading from a SpanReader. */
template<typename BS>
std::vector<DepGraphIndex> ReadLinearization(const DepGraph<BS>& depgraph, SpanReader& reader, bool topological=true)
{
std::vector<DepGraphIndex> linearization;
TestBitSet todo = depgraph.Positions();
// In every iteration one transaction is appended to linearization.
while (todo.Any()) {
// Compute the set of transactions to select from.
TestBitSet potential_next;
if (topological) {
// Find all transactions with no not-yet-included ancestors.
for (auto j : todo) {
if ((depgraph.Ancestors(j) & todo) == TestBitSet::Singleton(j)) {
potential_next.Set(j);
}
}
} else {
// Allow any element to be selected next, regardless of topology.
potential_next = todo;
}
// There must always be one (otherwise there is a cycle in the graph).
assert(potential_next.Any());
// Read a number from reader, and interpret it as index into potential_next.
uint64_t idx{0};
try {
reader >> VARINT(idx);
} catch (const std::ios_base::failure&) {}
idx %= potential_next.Count();
// Find out which transaction that corresponds to.
for (auto j : potential_next) {
if (idx == 0) {
// When found, add it to linearization and remove it from todo.
linearization.push_back(j);
assert(todo[j]);
todo.Reset(j);
break;
}
--idx;
}
}
return linearization;
}
/** Given a dependency graph, construct a tree-structured graph.
*
* Copies the nodes from the depgraph, but only keeps the first parent (even direction)
* or the first child (odd direction) for each transaction.
*/
template<typename BS>
DepGraph<BS> BuildTreeGraph(const DepGraph<BS>& depgraph, uint8_t direction)
{
DepGraph<BS> depgraph_tree;
for (DepGraphIndex i = 0; i < depgraph.PositionRange(); ++i) {
if (depgraph.Positions()[i]) {
depgraph_tree.AddTransaction(depgraph.FeeRate(i));
} else {
// For holes, add a dummy transaction which is deleted below, so that non-hole
// transactions retain their position.
depgraph_tree.AddTransaction(FeeFrac{});
}
}
depgraph_tree.RemoveTransactions(BS::Fill(depgraph.PositionRange()) - depgraph.Positions());
if (direction & 1) {
for (DepGraphIndex i : depgraph.Positions()) {
auto children = depgraph.GetReducedChildren(i);
if (children.Any()) {
depgraph_tree.AddDependencies(BS::Singleton(i), children.First());
}
}
} else {
for (DepGraphIndex i : depgraph.Positions()) {
auto parents = depgraph.GetReducedParents(i);
if (parents.Any()) {
depgraph_tree.AddDependencies(BS::Singleton(parents.First()), i);
}
}
}
return depgraph_tree;
}
} // namespace
FUZZ_TARGET(clusterlin_depgraph_sim)
{
// Simulation test to verify the full behavior of DepGraph.
FuzzedDataProvider provider(buffer.data(), buffer.size());
/** Real DepGraph being tested. */
DepGraph<TestBitSet> real;
/** Simulated DepGraph (sim[i] is std::nullopt if position i does not exist; otherwise,
* sim[i]->first is its individual feerate, and sim[i]->second is its set of ancestors. */
std::array<std::optional<std::pair<FeeFrac, TestBitSet>>, TestBitSet::Size()> sim;
/** The number of non-nullopt position in sim. */
DepGraphIndex num_tx_sim{0};
/** Read a valid index of a transaction from the provider. */
auto idx_fn = [&]() {
auto offset = provider.ConsumeIntegralInRange<DepGraphIndex>(0, num_tx_sim - 1);
for (DepGraphIndex i = 0; i < sim.size(); ++i) {
if (!sim[i].has_value()) continue;
if (offset == 0) return i;
--offset;
}
assert(false);
return DepGraphIndex(-1);
};
/** Read a valid subset of the transactions from the provider. */
auto subset_fn = [&]() {
auto range = (uint64_t{1} << num_tx_sim) - 1;
const auto mask = provider.ConsumeIntegralInRange<uint64_t>(0, range);
auto mask_shifted = mask;
TestBitSet subset;
for (DepGraphIndex i = 0; i < sim.size(); ++i) {
if (!sim[i].has_value()) continue;
if (mask_shifted & 1) {
subset.Set(i);
}
mask_shifted >>= 1;
}
assert(mask_shifted == 0);
return subset;
};
/** Read any set of transactions from the provider (including unused positions). */
auto set_fn = [&]() {
auto range = (uint64_t{1} << sim.size()) - 1;
const auto mask = provider.ConsumeIntegralInRange<uint64_t>(0, range);
TestBitSet set;
for (DepGraphIndex i = 0; i < sim.size(); ++i) {
if ((mask >> i) & 1) {
set.Set(i);
}
}
return set;
};
/** Propagate ancestor information in sim. */
auto anc_update_fn = [&]() {
while (true) {
bool updates{false};
for (DepGraphIndex chl = 0; chl < sim.size(); ++chl) {
if (!sim[chl].has_value()) continue;
for (auto par : sim[chl]->second) {
if (!sim[chl]->second.IsSupersetOf(sim[par]->second)) {
sim[chl]->second |= sim[par]->second;
updates = true;
}
}
}
if (!updates) break;
}
};
/** Compare the state of transaction i in the simulation with the real one. */
auto check_fn = [&](DepGraphIndex i) {
// Compare used positions.
assert(real.Positions()[i] == sim[i].has_value());
if (sim[i].has_value()) {
// Compare feerate.
assert(real.FeeRate(i) == sim[i]->first);
// Compare ancestors (note that SanityCheck verifies correspondence between ancestors
// and descendants, so we can restrict ourselves to ancestors here).
assert(real.Ancestors(i) == sim[i]->second);
}
};
auto last_compaction_pos{real.PositionRange()};
LIMITED_WHILE(provider.remaining_bytes() > 0, 1000) {
int command = provider.ConsumeIntegral<uint8_t>() % 4;
while (true) {
// Iterate decreasing command until an applicable branch is found.
if (num_tx_sim < TestBitSet::Size() && command-- == 0) {
// AddTransaction.
auto fee = provider.ConsumeIntegralInRange<int64_t>(-0x8000000000000, 0x7ffffffffffff);
auto size = provider.ConsumeIntegralInRange<int32_t>(1, 0x3fffff);
FeeFrac feerate{fee, size};
// Apply to DepGraph.
auto idx = real.AddTransaction(feerate);
// Verify that the returned index is correct.
assert(!sim[idx].has_value());
for (DepGraphIndex i = 0; i < TestBitSet::Size(); ++i) {
if (!sim[i].has_value()) {
assert(idx == i);
break;
}
}
// Update sim.
sim[idx] = {feerate, TestBitSet::Singleton(idx)};
++num_tx_sim;
break;
} else if (num_tx_sim > 0 && command-- == 0) {
// AddDependencies.
DepGraphIndex child = idx_fn();
auto parents = subset_fn();
// Apply to DepGraph.
real.AddDependencies(parents, child);
// Apply to sim.
sim[child]->second |= parents;
break;
} else if (num_tx_sim > 0 && command-- == 0) {
// Remove transactions.
auto del = set_fn();
// Propagate all ancestry information before deleting anything in the simulation (as
// intermediary transactions may be deleted which impact connectivity).
anc_update_fn();
// Compare the state of the transactions being deleted.
for (auto i : del) check_fn(i);
// Apply to DepGraph.
real.RemoveTransactions(del);
// Apply to sim.
for (DepGraphIndex i = 0; i < sim.size(); ++i) {
if (sim[i].has_value()) {
if (del[i]) {
--num_tx_sim;
sim[i] = std::nullopt;
} else {
sim[i]->second -= del;
}
}
}
break;
} else if (command-- == 0) {
// Compact.
const size_t mem_before{real.DynamicMemoryUsage()};
real.Compact();
const size_t mem_after{real.DynamicMemoryUsage()};
assert(real.PositionRange() < last_compaction_pos ? mem_after < mem_before : mem_after <= mem_before);
last_compaction_pos = real.PositionRange();
break;
}
}
}
// Compare the real obtained depgraph against the simulation.
anc_update_fn();
for (DepGraphIndex i = 0; i < sim.size(); ++i) check_fn(i);
assert(real.TxCount() == num_tx_sim);
// Sanity check the result (which includes round-tripping serialization, if applicable).
SanityCheck(real);
}
FUZZ_TARGET(clusterlin_depgraph_serialization)
{
// Verify that any deserialized depgraph is acyclic and roundtrips to an identical depgraph.
// Construct a graph by deserializing.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
DepGraphIndex par_code{0}, chl_code{0};
try {
reader >> Using<DepGraphFormatter>(depgraph) >> VARINT(par_code) >> VARINT(chl_code);
} catch (const std::ios_base::failure&) {}
SanityCheck(depgraph);
// Verify the graph is a DAG.
assert(depgraph.IsAcyclic());
// Introduce a cycle, and then test that IsAcyclic returns false.
if (depgraph.TxCount() < 2) return;
DepGraphIndex par(0), chl(0);
// Pick any transaction of depgraph as parent.
par_code %= depgraph.TxCount();
for (auto i : depgraph.Positions()) {
if (par_code == 0) {
par = i;
break;
}
--par_code;
}
// Pick any ancestor of par (excluding itself) as child, if any.
auto ancestors = depgraph.Ancestors(par) - TestBitSet::Singleton(par);
if (ancestors.None()) return;
chl_code %= ancestors.Count();
for (auto i : ancestors) {
if (chl_code == 0) {
chl = i;
break;
}
--chl_code;
}
// Add the cycle-introducing dependency.
depgraph.AddDependencies(TestBitSet::Singleton(par), chl);
// Check that we now detect a cycle.
assert(!depgraph.IsAcyclic());
}
FUZZ_TARGET(clusterlin_components)
{
// Verify the behavior of DepGraphs's FindConnectedComponent and IsConnected functions.
// Construct a depgraph.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
std::vector<DepGraphIndex> linearization;
try {
reader >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
TestBitSet todo = depgraph.Positions();
while (todo.Any()) {
// Pick a transaction in todo, or nothing.
std::optional<DepGraphIndex> picked;
{
uint64_t picked_num{0};
try {
reader >> VARINT(picked_num);
} catch (const std::ios_base::failure&) {}
if (picked_num < todo.Size() && todo[picked_num]) {
picked = picked_num;
}
}
// Find a connected component inside todo, including picked if any.
auto component = picked ? depgraph.GetConnectedComponent(todo, *picked)
: depgraph.FindConnectedComponent(todo);
// The component must be a subset of todo and non-empty.
assert(component.IsSubsetOf(todo));
assert(component.Any());
// If picked was provided, the component must include it.
if (picked) assert(component[*picked]);
// If todo is the entire graph, and the entire graph is connected, then the component must
// be the entire graph.
if (todo == depgraph.Positions()) {
assert((component == todo) == depgraph.IsConnected());
}
// If subset is connected, then component must match subset.
assert((component == todo) == depgraph.IsConnected(todo));
// The component cannot have any ancestors or descendants outside of component but in todo.
for (auto i : component) {
assert((depgraph.Ancestors(i) & todo).IsSubsetOf(component));
assert((depgraph.Descendants(i) & todo).IsSubsetOf(component));
}
// Starting from any component element, we must be able to reach every element.
for (auto i : component) {
// Start with just i as reachable.
TestBitSet reachable = TestBitSet::Singleton(i);
// Add in-todo descendants and ancestors to reachable until it does not change anymore.
while (true) {
TestBitSet new_reachable = reachable;
for (auto j : new_reachable) {
new_reachable |= depgraph.Ancestors(j) & todo;
new_reachable |= depgraph.Descendants(j) & todo;
}
if (new_reachable == reachable) break;
reachable = new_reachable;
}
// Verify that the result is the entire component.
assert(component == reachable);
}
// Construct an arbitrary subset of todo.
uint64_t subset_bits{0};
try {
reader >> VARINT(subset_bits);
} catch (const std::ios_base::failure&) {}
TestBitSet subset;
for (DepGraphIndex i : depgraph.Positions()) {
if (todo[i]) {
if (subset_bits & 1) subset.Set(i);
subset_bits >>= 1;
}
}
// Which must be non-empty.
if (subset.None()) subset = TestBitSet::Singleton(todo.First());
// Remove it from todo.
todo -= subset;
}
// No components can be found in an empty subset.
assert(depgraph.FindConnectedComponent(todo).None());
}
FUZZ_TARGET(clusterlin_make_connected)
{
// Verify that MakeConnected makes graphs connected.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
try {
reader >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
MakeConnected(depgraph);
SanityCheck(depgraph);
assert(depgraph.IsConnected());
}
FUZZ_TARGET(clusterlin_chunking)
{
// Verify the correctness of the ChunkLinearization function.
// Construct a graph by deserializing.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
try {
reader >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
// Read a valid linearization for depgraph.
auto linearization = ReadLinearization(depgraph, reader);
// Invoke the chunking functions.
auto chunking = ChunkLinearization(depgraph, linearization);
auto chunking_info = ChunkLinearizationInfo(depgraph, linearization);
// Verify consistency between the two functions.
assert(chunking.size() == chunking_info.size());
for (size_t i = 0; i < chunking.size(); ++i) {
assert(chunking[i] == chunking_info[i].feerate);
assert(SetInfo(depgraph, chunking_info[i].transactions) == chunking_info[i]);
}
// Verify that chunk feerates are monotonically non-increasing.
for (size_t i = 1; i < chunking.size(); ++i) {
assert(!(chunking[i] >> chunking[i - 1]));
}
// Naively recompute the chunks (each is the highest-feerate prefix of what remains).
auto todo = depgraph.Positions();
for (const auto& [chunk_set, chunk_feerate] : chunking_info) {
assert(todo.Any());
SetInfo<TestBitSet> accumulator, best;
for (DepGraphIndex idx : linearization) {
if (todo[idx]) {
accumulator.Set(depgraph, idx);
if (best.feerate.IsEmpty() || accumulator.feerate >> best.feerate) {
best = accumulator;
}
}
}
assert(chunk_feerate == best.feerate);
assert(chunk_set == best.transactions);
assert(best.transactions.IsSubsetOf(todo));
todo -= best.transactions;
}
assert(todo.None());
}
static constexpr auto MAX_SIMPLE_ITERATIONS = 300000;
FUZZ_TARGET(clusterlin_simple_finder)
{
// Verify that SimpleCandidateFinder works as expected by sanity checking the results
// and comparing them (if claimed to be optimal) against the sets found by
// ExhaustiveCandidateFinder.
//
// Note that SimpleCandidateFinder is only used in tests; the purpose of this fuzz test is to
// establish confidence in SimpleCandidateFinder, so that it can be used in SimpleLinearize,
// which is then used to test Linearize below.
// Retrieve a depgraph from the fuzz input.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
try {
reader >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
// Instantiate the SimpleCandidateFinder to be tested, and the ExhaustiveCandidateFinder it is
// being tested against.
SimpleCandidateFinder smp_finder(depgraph);
ExhaustiveCandidateFinder exh_finder(depgraph);
auto todo = depgraph.Positions();
while (todo.Any()) {
assert(!smp_finder.AllDone());
assert(!exh_finder.AllDone());
// Call SimpleCandidateFinder.
auto [found, iterations_done] = smp_finder.FindCandidateSet(MAX_SIMPLE_ITERATIONS);
bool optimal = (iterations_done != MAX_SIMPLE_ITERATIONS);
// Sanity check the result.
assert(iterations_done <= MAX_SIMPLE_ITERATIONS);
assert(found.transactions.Any());
assert(found.transactions.IsSubsetOf(todo));
assert(depgraph.FeeRate(found.transactions) == found.feerate);
// Check that it is topologically valid.
for (auto i : found.transactions) {
assert(found.transactions.IsSupersetOf(depgraph.Ancestors(i) & todo));
}
// At most 2^(N-1) iterations can be required: the number of non-empty connected subsets a
// graph with N transactions can have. If MAX_SIMPLE_ITERATIONS exceeds this number, the
// result is necessarily optimal.
assert(iterations_done <= (uint64_t{1} << (todo.Count() - 1)));
if (MAX_SIMPLE_ITERATIONS > (uint64_t{1} << (todo.Count() - 1))) assert(optimal);
// SimpleCandidateFinder only finds connected sets.
assert(depgraph.IsConnected(found.transactions));
// Perform further quality checks only if SimpleCandidateFinder claims an optimal result.
if (optimal) {
if (todo.Count() <= 12) {
// Compare with ExhaustiveCandidateFinder. This quickly gets computationally
// expensive for large clusters (O(2^n)), so only do it for sufficiently small ones.
auto exhaustive = exh_finder.FindCandidateSet();
assert(exhaustive.feerate == found.feerate);
}
// Compare with a non-empty topological set read from the fuzz input (comparing with an
// empty set is not interesting).
auto read_topo = ReadTopologicalSet(depgraph, todo, reader, /*non_empty=*/true);
assert(found.feerate >= depgraph.FeeRate(read_topo));
}
// Find a non-empty topologically valid subset of transactions to remove from the graph.
// Using an empty set would mean the next iteration is identical to the current one, and
// could cause an infinite loop.
auto del_set = ReadTopologicalSet(depgraph, todo, reader, /*non_empty=*/true);
todo -= del_set;
smp_finder.MarkDone(del_set);
exh_finder.MarkDone(del_set);
}
assert(smp_finder.AllDone());
assert(exh_finder.AllDone());
}
FUZZ_TARGET(clusterlin_simple_linearize)
{
// Verify the behavior of SimpleLinearize(). Note that SimpleLinearize is only used in tests;
// the purpose of this fuzz test is to establish confidence in SimpleLinearize, so that it can
// be used to test the real Linearize function in the fuzz test below.
// Retrieve an iteration count and a depgraph from the fuzz input.
SpanReader reader(buffer);
uint64_t iter_count{0};
DepGraph<TestBitSet> depgraph;
try {
reader >> VARINT(iter_count) >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
iter_count %= MAX_SIMPLE_ITERATIONS;
// Invoke SimpleLinearize().
auto [linearization, optimal] = SimpleLinearize(depgraph, iter_count);
SanityCheck(depgraph, linearization);
auto simple_chunking = ChunkLinearization(depgraph, linearization);
// If the iteration count is sufficiently high, an optimal linearization must be found.
// SimpleLinearize on k transactions can take up to 2^(k-1) iterations (one per non-empty
// connected topologically valid subset), which sums over k=1..n to (2^n)-1.
const uint64_t n = depgraph.TxCount();
if (n <= 63 && (iter_count >> n)) {
assert(optimal);
}
// If SimpleLinearize claims optimal result, and the cluster is sufficiently small (there are
// n! linearizations), test that the result is as good as every valid linearization.
if (optimal && depgraph.TxCount() <= 8) {
auto exh_linearization = ExhaustiveLinearize(depgraph);
auto exh_chunking = ChunkLinearization(depgraph, exh_linearization);
auto cmp = CompareChunks(simple_chunking, exh_chunking);
assert(cmp == 0);
assert(simple_chunking.size() == exh_chunking.size());
}
if (optimal) {
// Compare with a linearization read from the fuzz input.
auto read = ReadLinearization(depgraph, reader);
auto read_chunking = ChunkLinearization(depgraph, read);
auto cmp = CompareChunks(simple_chunking, read_chunking);
assert(cmp >= 0);
}
}
FUZZ_TARGET(clusterlin_sfl)
{
// Verify the individual steps of the SFL algorithm.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
uint8_t flags{1};
uint64_t rng_seed{0};
try {
reader >> rng_seed >> flags >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
if (depgraph.TxCount() <= 1) return;
InsecureRandomContext rng(rng_seed);
/** Whether to make the depgraph connected. */
const bool make_connected = flags & 1;
/** Whether to load some input linearization into the state. */
const bool load_linearization = flags & 2;
/** Whether that input linearization is topological. */
const bool load_topological = load_linearization && (flags & 4);
// Initialize SFL state.
if (make_connected) MakeConnected(depgraph);
SpanningForestState sfl(depgraph, rng.rand64());
// Function to test the state.
std::vector<FeeFrac> last_diagram;
auto test_fn = [&](bool is_optimal = false) {
if (rng.randbits(4) == 0) {
// Perform sanity checks from time to time (too computationally expensive to do after
// every step).
sfl.SanityCheck(depgraph);
}
auto diagram = sfl.GetDiagram();
if (rng.randbits(4) == 0) {
// Verify that the diagram of GetLinearization() is at least as good as GetDiagram(),
// from time to time.
auto lin = sfl.GetLinearization();
auto lin_diagram = ChunkLinearization(depgraph, lin);
auto cmp_lin = CompareChunks(lin_diagram, diagram);
assert(cmp_lin >= 0);
// If we're in an allegedly optimal state, they must match.
if (is_optimal) assert(cmp_lin == 0);
}
// Verify that subsequent calls to GetDiagram() never get worse/incomparable.
if (!last_diagram.empty()) {
auto cmp = CompareChunks(diagram, last_diagram);
assert(cmp >= 0);
}
last_diagram = std::move(diagram);
};
if (load_linearization) {
auto input_lin = ReadLinearization(depgraph, reader, load_topological);
sfl.LoadLinearization(input_lin);
if (load_topological) {
// The diagram of the loaded linearization forms an initial lower bound on future
// diagrams.
last_diagram = ChunkLinearization(depgraph, input_lin);
} else {
// The input linearization may have been non-topological, so invoke MakeTopological to
// fix it still.
sfl.MakeTopological();
}
} else {
// Invoke MakeTopological to create an initial from-scratch topological state.
sfl.MakeTopological();
}
// Loop until optimal.
test_fn();
sfl.StartOptimizing();
while (true) {
test_fn();
if (!sfl.OptimizeStep()) break;
}
test_fn(/*is_optimal=*/true);
// Verify that optimality is reached within an expected amount of work. This protects against
// hypothetical bugs that hugely increase the amount of work needed to reach optimality.
assert(sfl.GetCost() <= MaxOptimalLinearizationIters(depgraph.TxCount()));
// The result must be as good as SimpleLinearize.
auto [simple_linearization, simple_optimal] = SimpleLinearize(depgraph, MAX_SIMPLE_ITERATIONS / 10);
auto simple_diagram = ChunkLinearization(depgraph, simple_linearization);
auto simple_cmp = CompareChunks(last_diagram, simple_diagram);
assert(simple_cmp >= 0);
if (simple_optimal) assert(simple_cmp == 0);
// We can compare with any arbitrary linearization, and the diagram must be at least as good as
// each.
for (int i = 0; i < 10; ++i) {
auto read_lin = ReadLinearization(depgraph, reader);
auto read_diagram = ChunkLinearization(depgraph, read_lin);
auto cmp = CompareChunks(last_diagram, read_diagram);
assert(cmp >= 0);
}
}
FUZZ_TARGET(clusterlin_linearize)
{
// Verify the behavior of Linearize().
// Retrieve an RNG seed, an iteration count, a depgraph, and whether to make it connected from
// the fuzz input.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
uint64_t rng_seed{0};
uint64_t iter_count{0};
uint8_t make_connected{1};
try {
reader >> VARINT(iter_count) >> Using<DepGraphFormatter>(depgraph) >> rng_seed >> make_connected;
} catch (const std::ios_base::failure&) {}
// The most complicated graphs are connected ones (other ones just split up). Optionally force
// the graph to be connected.
if (make_connected) MakeConnected(depgraph);
// Optionally construct an old linearization for it.
std::vector<DepGraphIndex> old_linearization;
{
uint8_t have_old_linearization{0};
try {
reader >> have_old_linearization;
} catch(const std::ios_base::failure&) {}
if (have_old_linearization & 1) {
old_linearization = ReadLinearization(depgraph, reader);
SanityCheck(depgraph, old_linearization);
}
}
// Invoke Linearize().
iter_count &= 0x7ffff;
auto [linearization, optimal, cost] = Linearize(depgraph, iter_count, rng_seed, old_linearization);
SanityCheck(depgraph, linearization);
auto chunking = ChunkLinearization(depgraph, linearization);
// Linearization must always be as good as the old one, if provided.
if (!old_linearization.empty()) {
auto old_chunking = ChunkLinearization(depgraph, old_linearization);
auto cmp = CompareChunks(chunking, old_chunking);
assert(cmp >= 0);
}
// If the iteration count is sufficiently high, an optimal linearization must be found.
if (iter_count > MaxOptimalLinearizationIters(depgraph.TxCount())) {
assert(optimal);
}
// If Linearize claims optimal result, run quality tests.
if (optimal) {
// It must be as good as SimpleLinearize.
auto [simple_linearization, simple_optimal] = SimpleLinearize(depgraph, MAX_SIMPLE_ITERATIONS);
SanityCheck(depgraph, simple_linearization);
auto simple_chunking = ChunkLinearization(depgraph, simple_linearization);
auto cmp = CompareChunks(chunking, simple_chunking);
assert(cmp >= 0);
// If SimpleLinearize finds the optimal result too, they must be equal (if not,
// SimpleLinearize is broken).
if (simple_optimal) assert(cmp == 0);
// Temporarily disabled, as Linearize() currently does not guarantee minimal chunks, even
// when it reports an optimal result. This will be re-introduced in a later commit.
//
// // If simple_chunking is diagram-optimal, it cannot have more chunks than chunking (as
// // chunking is claimed to be optimal, which implies minimal chunks).
// if (cmp == 0) assert(chunking.size() >= simple_chunking.size());
// Compare with a linearization read from the fuzz input.
auto read = ReadLinearization(depgraph, reader);
auto read_chunking = ChunkLinearization(depgraph, read);
auto cmp_read = CompareChunks(chunking, read_chunking);
assert(cmp_read >= 0);
}
}
FUZZ_TARGET(clusterlin_postlinearize)
{
// Verify expected properties of PostLinearize() on arbitrary linearizations.
// Retrieve a depgraph from the fuzz input.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
try {
reader >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
// Retrieve a linearization from the fuzz input.
std::vector<DepGraphIndex> linearization;
linearization = ReadLinearization(depgraph, reader);
SanityCheck(depgraph, linearization);
// Produce a post-processed version.
auto post_linearization = linearization;
PostLinearize(depgraph, post_linearization);
SanityCheck(depgraph, post_linearization);
// Compare diagrams: post-linearization cannot worsen anywhere.
auto chunking = ChunkLinearization(depgraph, linearization);
auto post_chunking = ChunkLinearization(depgraph, post_linearization);
auto cmp = CompareChunks(post_chunking, chunking);
assert(cmp >= 0);
// Run again, things can keep improving (and never get worse)
auto post_post_linearization = post_linearization;
PostLinearize(depgraph, post_post_linearization);
SanityCheck(depgraph, post_post_linearization);
auto post_post_chunking = ChunkLinearization(depgraph, post_post_linearization);
cmp = CompareChunks(post_post_chunking, post_chunking);
assert(cmp >= 0);
// The chunks that come out of postlinearizing are always connected.
auto linchunking = ChunkLinearizationInfo(depgraph, post_linearization);
for (const auto& [chunk_set, _chunk_feerate] : linchunking) {
assert(depgraph.IsConnected(chunk_set));
}
}
FUZZ_TARGET(clusterlin_postlinearize_tree)
{
// Verify expected properties of PostLinearize() on linearizations of graphs that form either
// an upright or reverse tree structure.
// Construct a direction, RNG seed, and an arbitrary graph from the fuzz input.
SpanReader reader(buffer);
uint64_t rng_seed{0};
DepGraph<TestBitSet> depgraph_gen;
uint8_t direction{0};
try {
reader >> direction >> rng_seed >> Using<DepGraphFormatter>(depgraph_gen);
} catch (const std::ios_base::failure&) {}
auto depgraph_tree = BuildTreeGraph(depgraph_gen, direction);
// Retrieve a linearization from the fuzz input.
std::vector<DepGraphIndex> linearization;
linearization = ReadLinearization(depgraph_tree, reader);
SanityCheck(depgraph_tree, linearization);
// Produce a postlinearized version.
auto post_linearization = linearization;
PostLinearize(depgraph_tree, post_linearization);
SanityCheck(depgraph_tree, post_linearization);
// Compare diagrams.
auto chunking = ChunkLinearization(depgraph_tree, linearization);
auto post_chunking = ChunkLinearization(depgraph_tree, post_linearization);
auto cmp = CompareChunks(post_chunking, chunking);
assert(cmp >= 0);
// Verify that post-linearizing again does not change the diagram. The result must be identical
// as post_linearization ought to be optimal already with a tree-structured graph.
auto post_post_linearization = post_linearization;
PostLinearize(depgraph_tree, post_post_linearization);
SanityCheck(depgraph_tree, post_post_linearization);
auto post_post_chunking = ChunkLinearization(depgraph_tree, post_post_linearization);
auto cmp_post = CompareChunks(post_post_chunking, post_chunking);
assert(cmp_post == 0);
// Try to find an even better linearization directly. This must not change the diagram for the
// same reason.
auto [opt_linearization, _optimal, _cost] = Linearize(depgraph_tree, 100000, rng_seed, post_linearization);
auto opt_chunking = ChunkLinearization(depgraph_tree, opt_linearization);
auto cmp_opt = CompareChunks(opt_chunking, post_chunking);
assert(cmp_opt == 0);
}
FUZZ_TARGET(clusterlin_postlinearize_moved_leaf)
{
// Verify that taking an existing linearization, and moving a leaf to the back, potentially
// increasing its fee, and then post-linearizing, results in something as good as the
// original. This guarantees that in an RBF that replaces a transaction with one of the same
// size but higher fee, applying the "remove conflicts, append new transaction, postlinearize"
// process will never worsen linearization quality.
// Construct an arbitrary graph and a fee from the fuzz input.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
int32_t fee_inc{0};
try {
uint64_t fee_inc_code;
reader >> Using<DepGraphFormatter>(depgraph) >> VARINT(fee_inc_code);
fee_inc = fee_inc_code & 0x3ffff;
} catch (const std::ios_base::failure&) {}
if (depgraph.TxCount() == 0) return;
// Retrieve two linearizations from the fuzz input.
auto lin = ReadLinearization(depgraph, reader);
auto lin_leaf = ReadLinearization(depgraph, reader);
// Construct a linearization identical to lin, but with the tail end of lin_leaf moved to the
// back.
std::vector<DepGraphIndex> lin_moved;
for (auto i : lin) {
if (i != lin_leaf.back()) lin_moved.push_back(i);
}
lin_moved.push_back(lin_leaf.back());
// Postlinearize lin_moved.
PostLinearize(depgraph, lin_moved);
SanityCheck(depgraph, lin_moved);
// Compare diagrams (applying the fee delta after computing the old one).
auto old_chunking = ChunkLinearization(depgraph, lin);
depgraph.FeeRate(lin_leaf.back()).fee += fee_inc;
auto new_chunking = ChunkLinearization(depgraph, lin_moved);
auto cmp = CompareChunks(new_chunking, old_chunking);
assert(cmp >= 0);
}
FUZZ_TARGET(clusterlin_fix_linearization)
{
// Verify expected properties of FixLinearization() on arbitrary linearizations.
// Retrieve a depgraph from the fuzz input.
SpanReader reader(buffer);
DepGraph<TestBitSet> depgraph;
try {
reader >> Using<DepGraphFormatter>(depgraph);
} catch (const std::ios_base::failure&) {}
// Construct an arbitrary linearization (not necessarily topological for depgraph).
std::vector<DepGraphIndex> linearization = ReadLinearization(depgraph, reader, /*topological=*/false);
assert(linearization.size() == depgraph.TxCount());
// Determine what prefix of linearization is topological, i.e., the position of the first entry
// in linearization which corresponds to a transaction that is not preceded by all its
// ancestors.
size_t topo_prefix = 0;
auto todo = depgraph.Positions();
while (topo_prefix < linearization.size()) {
DepGraphIndex idx = linearization[topo_prefix];
todo.Reset(idx);
if (todo.Overlaps(depgraph.Ancestors(idx))) break;
++topo_prefix;
}
// Then make a fixed copy of linearization.
auto linearization_fixed = linearization;
FixLinearization(depgraph, linearization_fixed);
// Sanity check it (which includes testing whether it is topological).
SanityCheck(depgraph, linearization_fixed);
// FixLinearization does not modify the topological prefix of linearization.
assert(std::equal(linearization.begin(), linearization.begin() + topo_prefix,
linearization_fixed.begin()));
// This also means that if linearization was entirely topological, FixLinearization cannot have
// modified it. This is implied by the assertion above already, but repeat it explicitly.
if (topo_prefix == linearization.size()) {
assert(linearization == linearization_fixed);
}
}