8000 BUG: exp and log cast float16 to float32 · Issue #13493 · numpy/numpy · GitHub
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toslunar opened this issue May 7, 2019 · 8 comments · Fixed by #13495
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BUG: exp and log cast float16 to float32 #13493

toslunar opened this issue May 7, 2019 · 8 comments · Fixed by #13495
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00 - Bug 06 - Regression

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@toslunar
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toslunar commented May 7, 2019

After #13134 is merged, np.exp and np.log return float32 arrays for float16 inputs. Is the change intended? I could not find docs for it (https://www.numpy.org/devdocs/reference/generated/numpy.exp.html), while it is documented that np.sum casts ints to the default platform integer.

Reproducing code example:

import numpy as np
print(np.exp(np.array([1, 2], np.float16)).dtype)  # => float32
print(np.log(np.array([1, 2], np.float16)).dtype)  # => float32

Numpy/Python version information:

1.17.0.dev0+64b3e67 3.7.1 (default, Nov  6 2018, 21:02:07)
[Clang 10.0.0 (clang-1000.10.44.4)]
@charris charris added this to the 1.17.0 release milestone May 7, 2019
@charris
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charris commented May 7, 2019

Looks like an unintended change. @r-devulap @mattip Thoughts? Maybe we need some tests...

@mattip
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mattip commented May 7, 2019

Adding tests and looking for a fix

@r-devulap
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Looking into it ..

@seberg
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seberg commented May 7, 2019

I am sure you already got it, but it will be because of the linear search of the loops, if the "f,f->f" loops are registered first, they are found instead of the "e,e->e" loops.

@seberg
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seberg commented May 7, 2019

Sorry for the spam. (compare also np.sqrt which currently has a funny loop duplication, but not this issue).

@mattip
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mattip commented May 7, 2019

I thought changing the type to TD('f', astype={'e':'f'}, simd=[('avx2', 'f'), ('avx512f', 'f')]) (adding the astype kwarg) would have solved it, but the test is still failing. Somehow the simd part is not respecting the astype

@mattip
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mattip commented May 7, 2019

Got it, need to not use simd on 'e' which makes sense

@mattip mattip changed the title exp and log cast float16 to float32 BUG: exp and log cast float16 to float32 May 7, 2019
@mattip mattip mentioned this issue May 7, 2019
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@r-devulap
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that was quick! thank you @mattip :)

@r-devulap r-devulap mentioned this issue May 7, 2019
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BUG: test all ufunc.types for return type, fix for exp, log mattip/numpy
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