[Numpy-discussion] numexpr with the new iterator

Mark Wiebe mwwiebe at gmail.com
Mon Jan 10 11:54:16 EST 2011

On Mon, Jan 10, 2011 at 2:05 AM, Francesc Alted <faltet at pytables.org> wrote:

> <snip>
> Your patch looks mostly fine to my eyes; good job!  Unfortunately, I've
> been unable to compile your new_iterator branch of NumPy:
> numpy/core/src/multiarray/multiarraymodule.c:45:33: fatal error:
> new_iterator_pywrap.h: El fitxer o directori no existeix
> Apparently, you forgot to add the new_iterator_pywrap.h file.

Oops,  that's added now.

> My idea would be to merge your patch in numexpr and make the new
> `evaluate_iter()` the default (i.e. make it `evaluate()`).  However, by
> looking into the code, it seems to me that unaligned arrays (this is an
> important use case when operating with columns of structured arrays) may
> need more fine-tuning for Intel platforms.  When I can compile the
> new_iterator branch, I'll give a try at unaligned data benchs.

The aligned case should just be a matter of conditionally removing the
NPY_ITER_ALIGNED flag in two places.

The new code also needs support for the reduce operation.  I didn't look too
closely at the code for that, but a nested iteration pattern is probably
appropriate.  If the inner loop is just allowed to be one dimension, it
could be done without actually creating the inner iterator.

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