BUG: Fix rfft for even input length. #26354
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WarrenWeckesser
added
component: numpy.fft
C++
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mac failure is an unrelated heisenbug |
charris
reviewed
Apr 27, 2024
numpy/fft/tests/test_pocketfft.py
Outdated
| def test_rfft_even(self): | ||
| x = np.arange(8) | ||
| y = np.fft.rfft(x, 4) | ||
| assert_allclose(y, [6.0, -2.0+2.0j, -2.0], rtol=1e-14) |
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Could use the same sort of test as for the odd case, I like comparing to the full complex fft case.
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Thanks Warren. |
mhvk
reviewed
Apr 27, 2024
| @@ -183,12 +183,15 @@ rfft_impl(char **args, npy_intp const *dimensions, npy_intp const *steps, | |||
| * Pocketfft uses FFTpack order, R0,R1,I1,...Rn-1,In-1,Rn[,In] (last | |||
| * for npts odd only). To make unpacking easy, we place the real data | |||
| * offset by one in the buffer, so that we just have to move R0 and | |||
| * create I0=0. Note that copy_data will zero the In component for | |||
| * create I0=0. Note that copy_input will zero the In component for | |||
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This is weird - so, the statement I made in the comment is not true? I'll try to have a quick look, but in any case the fix clearly works.
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#26359 does a follow-up that ensures the code actually does what the comment states. Would be nice to have both this one and #26359 be in 2.0.0.... Must admit that overall rewriting the fft routines in terms of ufuncs has been more of an experience in how hard it is to write bug-free code than I would have liked... Sorry all! |
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Closes gh-26349