[Numpy-discussion] Byte aligned arrays

Nathaniel Smith njs@pobox....
Wed Dec 19 12:48:29 CST 2012

On Wed, Dec 19, 2012 at 6:25 PM, Henry Gomersall <heng@cantab.net> wrote:
> On Wed, 2012-12-19 at 19:03 +0100, Francesc Alted wrote:
> <snip>
>> > Finally, I think there is significant value in auto-aligning the
>> array
>> > based on an appropriate inspection of the cpu capabilities (or
>> > alternatively, a function that reports back the appropriate SIMD
>> > alignment). Again, this makes it easier to wrap libraries that may
>> > function with any alignment, but benefit from optimum alignment.
>> Hmm, NumPy seems to return data blocks that are aligned to 16 bytes
>> on
>> systems (Linux and Mac OSX):
> <snip>
> That is not true at least under Windows 32-bit. I think also it's not
> true for Linux 32-bit from my vague recollections of testing in a
> virtual machine. (disclaimer: both those statements _may_ be out of
> date).
> But yes, under Linux 64-bit I always get my arrays aligned to 16 bytes.

Currently numpy just uses whatever the system malloc() returns, so the
alignment guarantees are entirely determined by your libc.


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