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Test the NUFFT adjoint against the scale of its inner products #169

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Merged
mcencini merged 1 commit into from
Nov 3, 2026
Merged

Test the NUFFT adjoint against the scale of its inner products #169

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14 changes: 10 additions & 4 deletions tests/test_finufft.py
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,12 @@ def _inner(a, b):
return torch.vdot(a.flatten(), b.flatten()).real.item()


def _assert_adjoint_pair(ax, y, x, ahy, rel):
"""<Ax, y> equals <x, A^H y> to `rel` of |Ax| |y|, the scale of either side."""
scale = torch.linalg.vector_norm(ax).item() * torch.linalg.vector_norm(y).item()
assert abs(_inner(ax, y) - _inner(x, ahy)) <= rel * scale


@requires_finufft
def test_matches_an_explicit_dft_on_a_radial_trajectory():
n = 64
Expand Down Expand Up @@ -135,7 +141,7 @@ def test_adjoint_identity_holds():
A = linop.NUFFT(traj, (1, n, n), toeplitz=False)
x = torch.randn(*A.ishape, dtype=torch.complex64)
y = torch.randn(*A.oshape, dtype=torch.complex64)
assert _inner(A(x), y) == pytest.approx(_inner(x, A.adjoint(y)), rel=1e-3)
_assert_adjoint_pair(A(x), y, x, A.adjoint(y), rel=1e-3)


@requires_finufft
Expand Down Expand Up @@ -235,7 +241,7 @@ def test_the_substituted_operator_is_its_own_adjoint_pair(in_tools):
ax = bartorch.nufft(x, traj)
ahy = bartorch.nufft_adjoint(y, traj, (1, n, n))

assert _inner(ax, y) == pytest.approx(_inner(x, ahy), rel=1e-4)
_assert_adjoint_pair(ax, y, x, ahy, rel=1e-4)


@requires_finufft
Expand All @@ -256,7 +262,7 @@ def test_weights_multiply_the_transform_and_their_conjugate_its_adjoint(in_tools
k = torch.randn(spokes, n, 1, dtype=torch.complex64)
adjoint = bartorch.nufft_adjoint(k, traj, (1, n, n), p=weights)
forward = bartorch.nufft(x, traj, p=weights)
assert _inner(forward, k) == pytest.approx(_inner(x, adjoint), rel=1e-4)
_assert_adjoint_pair(forward, k, x, adjoint, rel=1e-4)


@requires_finufft
Expand Down Expand Up @@ -1972,7 +1978,7 @@ def test_encoding_axes_behind_a_batch_are_transformed_a_batch_item_at_a_time():
y = torch.randn(*A.oshape, dtype=torch.complex64)
torch.testing.assert_close(A(x), torch.stack([one(x[c]) for c in range(coils)]))
torch.testing.assert_close(A.adjoint(y), torch.stack([one.adjoint(y[c]) for c in range(coils)]))
assert _inner(A(x), y) == pytest.approx(_inner(x, A.adjoint(y)), rel=1e-3)
_assert_adjoint_pair(A(x), y, x, A.adjoint(y), rel=1e-3)


def test_a_failed_install_is_reported_as_the_refusal_it_leads_to(monkeypatch, caplog):
Expand Down
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