Fix fractional centers in CircularConvolve #471
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Additional details and impacted files@@ Coverage Diff @@
## main #471 +/- ##
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- Coverage 94.57% 94.56% -0.02%
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Files 90 90
Lines 5585 5584 -1
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- Hits 5282 5280 -2
- Misses 303 304 +1
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bwohlberg
reviewed
Nov 15, 2023
scico/test/linop/test_circconv.py
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| def test_fractional_center(self): | ||
| """A fractional center should keep outputs real""" | ||
| x, _ = uniform(minval=-1, maxval=1, shape=(4, 5), key=self.key) | ||
| h, _ = uniform(minval=-1, maxval=1, shape=(2, 2), key=self.key) |
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It would be a bit better to not discard the key returned by the first call to unform, instead using it as the second key.
bwohlberg
approved these changes
Nov 15, 2023
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Using a fractional filter center for a
CircularConvolveoperator currently gives nonsense results. This PR adds a test for this nonsense (checking that the imaginary part of the result of filtering is small) and changes the way centers are handled to fix the problem. Relevant references:F. Candocia and J. C. Principe, "Comments on "Sinc interpolation of discrete periodic signals," in IEEE Transactions on Signal Processing, vol. 46, no. 7, pp. 2044-2047, July 1998, doi: 10.1109/78.700979.
"S. -C. Pei and Y. -C. Lai, "Closed Form Variable Fractional Time Delay Using FFT," in IEEE Signal Processing Letters, vol. 19, no. 5, pp. 299-302, May 2012, doi: 10.1109/LSP.2012.2191280.