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clusterlin: minimize chunks (feature)

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After the normal optimization process finishes, and finds an optimal
spanning forest, run a second process (while computation budget remains)
to split chunks into minimal equal-feerate chunks.
This commit is contained in:
Pieter Wuille
2025-10-14 16:15:19 -04:00
parent abc6a3a4eb
commit da56ef239b
5 changed files with 235 additions and 29 deletions
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32
src/test/fuzz/cluster_linearize.cpp
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@@ -914,7 +914,8 @@ FUZZ_TARGET(clusterlin_sfl)
// Function to test the state.
std::vector<FeeFrac> last_diagram;
auto test_fn = [&](bool is_optimal = false) {
bool was_optimal{false};
auto test_fn = [&](bool is_optimal = false, bool is_minimal = false) {
if (rng.randbits(4) == 0) {
// Perform sanity checks from time to time (too computationally expensive to do after
// every step).
@@ -930,13 +931,21 @@ FUZZ_TARGET(clusterlin_sfl)
assert(cmp_lin >= 0);
// If we're in an allegedly optimal state, they must match.
if (is_optimal) assert(cmp_lin == 0);
// If we're in an allegedly minimal state, they must also have the same number of
// segments.
if (is_minimal) assert(diagram.size() == lin_diagram.size());
}
// Verify that subsequent calls to GetDiagram() never get worse/incomparable.
if (!last_diagram.empty()) {
auto cmp = CompareChunks(diagram, last_diagram);
assert(cmp >= 0);
// If the last diagram was already optimal, the new one cannot be better.
if (was_optimal) assert(cmp == 0);
// Also, if the diagram was already optimal, the number of segments can only increase.
if (was_optimal) assert(diagram.size() >= last_diagram.size());
}
last_diagram = std::move(diagram);
was_optimal = is_optimal;
};
if (load_linearization) {
@@ -963,7 +972,15 @@ FUZZ_TARGET(clusterlin_sfl)
test_fn();
if (!sfl.OptimizeStep()) break;
}
// Loop until minimal.
test_fn(/*is_optimal=*/true);
sfl.StartMinimizing();
while (true) {
test_fn(/*is_optimal=*/true);
if (!sfl.MinimizeStep()) break;
}
test_fn(/*is_optimal=*/true, /*is_minimal=*/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.
@@ -975,6 +992,9 @@ FUZZ_TARGET(clusterlin_sfl)
auto simple_cmp = CompareChunks(last_diagram, simple_diagram);
assert(simple_cmp >= 0);
if (simple_optimal) assert(simple_cmp == 0);
// If the diagram matches, we must also have at least as many segments (because the SFL state
// and its produced diagram are minimal);
if (simple_cmp == 0) assert(last_diagram.size() >= simple_diagram.size());
// We can compare with any arbitrary linearization, and the diagram must be at least as good as
// each.
@@ -983,6 +1003,7 @@ FUZZ_TARGET(clusterlin_sfl)
auto read_diagram = ChunkLinearization(depgraph, read_lin);
auto cmp = CompareChunks(last_diagram, read_diagram);
assert(cmp >= 0);
if (cmp == 0) assert(last_diagram.size() >= read_diagram.size());
}
}
@@ -1052,12 +1073,9 @@ FUZZ_TARGET(clusterlin_linearize)
// 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());
// 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);