8000 BUG: Inaccurate `log1p` for small complex input · Issue #22609 · numpy/numpy · GitHub
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BUG: Inaccurate log1p for small complex input #22609

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mfkasim1 opened this issue Nov 17, 2022 · 0 comments · May be fixed by #22611 or #26798
Open

BUG: Inaccurate log1p for small complex input #22609

mfkasim1 opened this issue Nov 17, 2022 · 0 comments · May be fixed by #22611 or #26798
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00 - Bug

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@mfkasim1
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Describe the issue:

The reason for log1p existence is to provide a more numerically stable function for small input, compared to log(1 + x).
If the input is real valued, np.log1p can serve its purpose.
However, when the input is complex and small, np.log1p loses its accuracy.

Reproduce the code example:

import numpy as np
print(np.log1p(1e-18 + 1e-18j))  # wrongly produces 1e-18j, should be 1e-18 + 1e-18j

Error message:

No response

NumPy/Python version information:

1.23.4 3.9.15 (main, Nov 4 2022, 16:13:54) [GCC 11.2.0]

Context for the issue:

No response
@mfkasim1 mfkasim1 linked a pull request Nov 17, 2022 that will close this issue
Open
@seberg seberg mentioned this issue Nov 19, 2022
Closed
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Aug 14, 2023
@WarrenWeckesser
BUG: umath: Fix log1p for complex inputs.
2511f87 
Reimplement the complex log1p function.  Use the log1p trick from Theorem 4
of Goldberg's paper "What every computer scientist should know about
floating-point arithmetic".  Include special handling of an input with
imaginary part 0.0 to ensure the sign of the imaginary part of the result
is correct and consistent with the complex log function.

Closes numpygh-22609.
@WarrenWeckesser WarrenWeckesser mentioned this issue Aug 14, 2023
Closed
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 5, 2024
@WarrenWeckesser
BUG: umath: Fix log1p for complex inputs.
27b99f6 
Reimplement the complex log1p function.  Use the log1p trick from Theorem 4
of Goldberg's paper "What every computer scientist should know about
floating-point arithmetic".  Include special handling of an input with
imaginary part 0.0 to ensure the sign of the imaginary part of the result
is correct and consistent with the complex log function.

Closes numpygh-22609.
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 18, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
4791801 
Closes numpygh-22609
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 18, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
5c2a847 
Closes numpygh-22609

[skip circle]
@WarrenWeckesser WarrenWeckesser mentioned this issue Jun 18, 2024
Closed
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 22, 2024
@WarrenWeckesser
BUG: umath: Fix log1p for complex inputs.
2b1ca5e 
Reimplement the complex log1p function.  Use the log1p trick from Theorem 4
of Goldberg's paper "What every computer scientist should know about
floating-point arithmetic".  Include special handling of an input with
imaginary part 0.0 to ensure the sign of the imaginary part of the result
is correct and consistent with the complex log function.

Closes numpygh-22609.
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 22, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
1bebfe8 
Closes numpygh-22609
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 22, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
749acb3 
Closes numpygh-22609
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 26, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
4bcb4a1 
Closes numpygh-22609
@WarrenWeckesser WarrenWeckesser linked a pull request Jun 26, 2024 that will close this issue
Open
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 26, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
342a04a 
Closes numpygh-22609
WarrenWeckesser added a commit to WarrenWeckesser/numpy that referenced this issue Jun 27, 2024
@WarrenWeckesser
Rewrite complex log1p to improve precision.
33860e6 
Closes numpygh-22609
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