[Numpy-discussion] Numpy 1.9.1, zeros and alignement

Julian Taylor jtaylor.debian at googlemail.com
Tue Nov 18 13:40:39 EST 2014


< 1.9 lies about alignment it doesn't actually check for new arrays.

is the array aligned?

On 18.11.2014 19:37, David Cournapeau wrote:
> Additional point: it seems to always return aligned data on 1.8.1 (same
> platform/compiler/everything).
> 
> On Tue, Nov 18, 2014 at 6:35 PM, David Cournapeau <cournape at gmail.com
> <mailto:cournape at gmail.com>> wrote:
> 
>     It is on windows 32 bits, but I would need to make this work for
>     complex (pair of double) as well.
> 
>     Is this a bug (I  assumed array creation methods would always create
>     aligned arrays for their type) ? Seems like quite a bit of code out
>     there would assume this (scipy itself does for example).
> 
>     (the context is > 100 test failures on scipy 0.14.x on top of numpy
>     1.9., because f2py intent(inout) fails on work arrays created by
>     zeros, this is a windows-32 only failure).
> 
>     David
> 
>     On Tue, Nov 18, 2014 at 6:26 PM, Julian Taylor
>     <jtaylor.debian at googlemail.com
>     <mailto:jtaylor.debian at googlemail.com>> wrote:
> 
>         On 18.11.2014 19:20, David Cournapeau wrote:
>         > Hi,
>         >
>         > I have not followed closely the changes that happen in 1.9.1,
>         but was
>         > surprised by the following:
>         >
>         > x = np.zeros(12, "d")
>         > assert x.flags.aligned # fails
>         >
>         > This is running numpy 1.9.1 built on windows with VS 2008. Is it
>         > expected that zeros may return a non-aligned array ?
>         >
> 
>         what is the real alignment of the array? Are you on 32 bit or 64
>         bit?
>         What is the alignment of doubles in windows (linux its 4 byte on
>         32 bit
>         8 byte on 64 bit (% special compiler flags)?
>         print x.__array_interface__["data"]
> 
>         there are problems with complex types but doubles should be
>         aligned even
>         on 32 bit.
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> 
> 
> 
> 
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