8000 16-byte algined memory for NumPy development · Issue #7013 · numpy/numpy · GitHub
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16-byte algined memory for NumPy development #7013

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bashtage opened this issue Jan 15, 2016 · 3 comments
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16-byte algined memory for NumPy development #7013

bashtage opened this issue Jan 15, 2016 · 3 comments

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@bashtage
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Does anyone have any insights on getting 16 byte aligned memory (at least on x86/_64 systems)? I saw #1165 and #1166 but this doesn't seem to have gone anywhere.

I have implemented dSFMT as an alternative to the random-kit generator in an attempt at general structure for RandomState here https://github.com/bashtage/ng-numpy-randomstate/ . Unfortunately I can't use -DHAVE_SSE2 since on occasion the allocated memory is not aligned.

The obvious solution is to over allocate memory to ensure that the key array si 16-byte aligned, but this feels clumsy at best. If anyone has experience with this it would be appreciated.
@bashtage
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Found this reference for working with FFTW which suggests that overallocation and manual alignment is solution.

@juliantaylor
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btw. on x86_64 systems allocated memory is always 16 byte aligned
also modern intel and amd cpus don't care much about alignment anymore, that ended with the haswell

@bashtage
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Thanks - I'm surprised I missed #5312 which is almost exactly what I need, and done better than my one-off-solution.

I think alignment still matters when interfacing with 3rd party code which uses SSE2 intrinsics that require alignment (short of rewriting SSE2 parts of the code).

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