8000 BUG: log1p output has less precision for the real part of small complex inputs · Issue #21105 · numpy/numpy · GitHub
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BUG: log1p output has less precision for the real part of small complex inputs #21105

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vmagno opened this issue Feb 22, 2022 · 1 comment
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BUG: log1p output has less precision for the real part of small complex inputs #21105

vmagno opened this issue Feb 22, 2022 · 1 comment
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@vmagno
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vmagno commented Feb 22, 2022

Describe the issue:

The real part of the output of numpy.log1p is rounded down to zero when the real part of a complex input is less than about 1e-15. This does not occur for the imaginary part of a complex input/output, or when the input is real.
For example:

>>> import numpy as np
>>> np.log1p(1e-14 + 1e-14j)
(9.992007221626358e-15+9.9999999999999e-15j)
>>> np.log1p(1e-16 + 1e-16j)
1e-16j
>>> np.log1p(1e-16)
1e-16
>>> np.log1p(1e-16j)
1e-16j

This occurs on Linux with numpy version 1.22.2, and python version 3.10.2

Reproduce the code example:

import numpy as np
np.log1p(1e-14 + 1e-14j)
np.log1p(1e-16 + 1e-16j)
np.log1p(1e-16)
np.log1p(1e-16j)

Error message:

No response

NumPy/Python version information:

1.22.2 3.10.2 (main, Jan 15 2022, 19:56:27) [GCC 11.1.0]
@seberg
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seberg commented Nov 19, 2022

Identical to the newer gh-22609, closing this one as there is some activity.

@seberg seberg closed this as completed Nov 19, 2022
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