[Numpy-discussion] Openmp support (was numpy's future (1.1 and beyond): which direction(s) ?)

Charles R Harris charlesr.harris@gmail....
Sat Mar 22 13:12:17 CDT 2008


On Sat, Mar 22, 2008 at 12:01 PM, James Philbin <philbinj@gmail.com> wrote:

> >  gcc keeps advancing autovectorization.  Is manual vectorization worth
> the
> >  trouble?
>
> Well, the way that the ufuncs are written at the moment,
> -ftree-vectorize will never kick in due to the non-constant strides.
> To get this to work, one has to special case out unary strides. Even
> with constant strides -ftree-vectorize often produces sub-optimal code
> as it has to make very conservative assumptions about the content of
> variables (it can do better if -fstrict-aliasing is used, but I think


Numpy would die with strict-aliasing because it relies on casting char
pointers to various types. It might be possible to use void pointers, but
that would be a major do over and it isn't clear what the strides and
offsets, currently in char units, would become.

Chuck
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