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clusterlin: support fixing linearizations (feature)

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This also updates FixLinearization to just be a thin wrapper around Linearize.
In a future commit, FixLinearization will be removed entirely.
This commit is contained in:
Pieter Wuille
2025-10-23 19:16:50 -04:00
parent 755f0900a2
commit 01ffcf464a
3 changed files with 44 additions and 54 deletions
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44
src/test/fuzz/cluster_linearize.cpp
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@@ -998,35 +998,40 @@ FUZZ_TARGET(clusterlin_linearize)
DepGraph<TestBitSet> depgraph;
uint64_t rng_seed{0};
uint64_t iter_count{0};
uint8_t make_connected{1};
uint8_t flags{7};
try {
reader >> VARINT(iter_count) >> Using<DepGraphFormatter>(depgraph) >> rng_seed >> make_connected;
reader >> VARINT(iter_count) >> Using<DepGraphFormatter>(depgraph) >> rng_seed >> flags;
} catch (const std::ios_base::failure&) {}
bool make_connected = flags & 1;
// The following 3 booleans have 4 combinations:
// - (flags & 6) == 0: do not provide input linearization.
// - (flags & 6) == 2: provide potentially non-topological input.
// - (flags & 6) == 4: provide topological input linearization, but do not claim it is
// topological.
// - (flags & 6) == 6: provide topological input linearization, and claim it is topological.
bool provide_input = flags & 6;
bool provide_topological_input = flags & 4;
bool claim_topological_input = (flags & 6) == 6;
// 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);
}
if (provide_input) {
old_linearization = ReadLinearization(depgraph, reader, /*topological=*/provide_topological_input);
if (provide_topological_input) SanityCheck(depgraph, old_linearization);
}
// Invoke Linearize().
iter_count &= 0x7ffff;
auto [linearization, optimal, cost] = Linearize(depgraph, iter_count, rng_seed, old_linearization);
auto [linearization, optimal, cost] = Linearize(depgraph, iter_count, rng_seed, old_linearization, /*is_topological=*/claim_topological_input);
SanityCheck(depgraph, linearization);
auto chunking = ChunkLinearization(depgraph, linearization);
// Linearization must always be as good as the old one, if provided.
if (!old_linearization.empty()) {
// Linearization must always be as good as the old one, if provided and topological (even when
// not claimed to be topological).
if (provide_topological_input) {
auto old_chunking = ChunkLinearization(depgraph, old_linearization);
auto cmp = CompareChunks(chunking, old_chunking);
assert(cmp >= 0);
@@ -1231,12 +1236,11 @@ FUZZ_TARGET(clusterlin_fix_linearization)
// 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 linearization was entirely topological, FixLinearization cannot worsen it.
if (topo_prefix == linearization.size()) {
assert(linearization == linearization_fixed);
auto chunking = ChunkLinearization(depgraph, linearization);
auto chunking_fixed = ChunkLinearization(depgraph, linearization_fixed);
auto cmp = CompareChunks(chunking_fixed, chunking);
assert(cmp >= 0);
}
}