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Fix correlated matching boundary component handling #1

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Merged
noajshu merged 1 commit into from
Sep 25, 2025
Merged

Fix correlated matching boundary component handling #1

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8 changes: 6 additions & 2 deletions src/pymatching/sparse_blossom/driver/user_graph.h
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Original file line number Diff line number Diff line change
Expand Up @@ -321,8 +321,12 @@ void iter_dem_instructions_include_correlations(
"Encountered a decomposed error instruction with an undetectable component (0 detectors). "
"This is not supported.");
} else if (num_component_detectors > 0) {
// If the previous error in the decomposition had 1 or 2 detectors, we handle it
handle_dem_error(p, {component->node1, component->node2}, component->observable_indices);
// If the previous error in the decomposition had 1 or 2 detectors, we handle it.
if (component->node2 == SIZE_MAX) {
handle_dem_error(p, {component->node1}, component->observable_indices);
} else {
handle_dem_error(p, {component->node1, component->node2}, component->observable_indices);
}
decomposed_err.components.push_back({});
component = &decomposed_err.components.back();
component->node1 = SIZE_MAX;
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20 changes: 20 additions & 0 deletions tests/matching/decode_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -400,6 +400,26 @@ def test_decode_to_edges_with_correlations():
assert np.array_equal(edges, expected_edges)


def test_correlated_matching_handles_single_detector_components():
stim = pytest.importorskip("stim")
p = 0.1
circuit = stim.Circuit.generated(
code_task="surface_code:rotated_memory_x",
distance=5,
rounds=5,
before_round_data_depolarization=p,
)
circ_str = str(circuit).replace(
f"DEPOLARIZE1({p})", f"PAULI_CHANNEL_1(0, {p}, 0)"
)
noisy_circuit = stim.Circuit(circ_str)
dem = noisy_circuit.detector_error_model(
decompose_errors=True, approximate_disjoint_errors=True
)
m = Matching.from_detector_error_model(dem, enable_correlations=True)
assert m.num_detectors > 0


def test_load_from_circuit_with_correlations():
stim = pytest.importorskip("stim")
circuit = stim.Circuit.generated(
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