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test(pt_expt): tolerance for test_default_fallback (CUDA scatter nondeterminism) #5508

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Merged
njzjz merged 1 commit into from
Jun 9, 2026
Merged

test(pt_expt): tolerance for test_default_fallback (CUDA scatter nondeterminism) #5508

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16 changes: 14 additions & 2 deletions source/tests/pt_expt/utils/test_neighbor_list.py
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Original file line number Diff line number Diff line change
Expand Up @@ -476,7 +476,17 @@ def test_pt_expt_multiframe_equivalence(name: str) -> None:

@pytest.mark.parametrize("name", list(ALL_MODELS)) # descriptor family
def test_default_fallback(name: str) -> None:
"""``neighbor_list=None`` equals an explicit DefaultNeighborList byte-for-byte."""
"""``neighbor_list=None`` dispatches to the same DefaultNeighborList builder.

``None`` and an explicit ``DefaultNeighborList()`` are the identical builder
(``call_common`` does ``builder = nl if nl is not None else DefaultNeighborList()``),
so the two forward passes are the *same computation*; on CPU they are
bit-identical. We compare with a tight tolerance rather than exact equality
because the two passes are independent forward evaluations, and on CUDA the
GNN message-passing scatter (atomic adds) is not bit-reproducible run-to-run,
so the virial can differ by ~1 ULP between the passes (a real dispatch bug
would differ by orders of magnitude more).
"""
coord_np, atype_np, box_np = _system()
md = get_model(copy.deepcopy(ALL_MODELS[name])).to(env.DEVICE)
md.eval()
Expand All @@ -492,8 +502,10 @@ def test_default_fallback(name: str) -> None:
).requires_grad_(True)
outs[tag] = md.forward(coord_t, atype_t, box=box_t, do_atomic_virial=True, **kw)
for k in ("energy", "force", "virial"):
np.testing.assert_array_equal(
np.testing.assert_allclose(
outs["none"][k].detach().cpu().numpy(),
outs["explicit"][k].detach().cpu().numpy(),
rtol=1e-10,
atol=1e-12,
err_msg=f"{name} {k}",
)
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