[Numpy-discussion] Psyco MA?

[Paul F D. <pa...@pf...>]

{ CC to GvR just to show why I'm +1 on the if-PEP. I liked this in =
another
language I used to use; Perl ? }

Perhaps knowlegeable persons could comment on the feasibility of coding =
MA
(masked arrays) in straight Python and then using Psyco on it? The =
existing
implementation is in pure python and uses Numeric to represent the two
arrays it holds (the data and sometimes a mask) in each object. A great =
deal
of wasted motion is devoted to preparing Numeric arrays so as to avoid
operations on masked elements.=20

It could have been written a lot simpler if performance didn't dictate
trying to leverage off Numeric. In straight Python one can imagine an =
add,
for example, that was roughly:
    for k in 0<=3D k < len(a.data):
       result.mask[k] =3D a.mask[k] or b.mask[k]
       result.data[k] =3D a.data[k] if result.mask[k] else a.data[k] +
b.data[k]

(using the new if expression PEP just to confuse the populace)

It seems to me that this might be competitive given the numbers someone
posted before. Alas, I can't remember who was the original poster, but =
I'd
guess they might have a good guess.

> -----Original Message-----
> From: num...@li...=20
> [mailto:num...@li...] On=20
> Behalf Of Chris Barker
> Sent: Friday, February 07, 2003 10:34 AM
> To: fa...@op...; num...@li...
> Subject: Re: [Psyco-devel] RE: [Numpy-discussion] Interesting=20
> Psyco/Numeric/Numarray comparison
>=20
>=20
> Francesc Alted wrote:
>=20
> > For this task may be is worth to consider using Pyrex
> > (http://www.cosc.canterbury.ac.nz/~greg/python/Pyrex/) for=20
> that. From=20
> > the
> > website:
> >=20
> > """Pyrex lets you write code that mixes Python and C data types any=20
> > way you want, and compiles it into a C extension for Python."""
>=20
> I've been keeping my eye on Pyrex for a while now, but have=20
> not yet had enough of a use for it to justify tryin git out.=20
> I do ahve a question that I ahve not foudn the answer to on=20
> the web, which could make a big difference to how useful it is to me:
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> Is Pyrex aware of Numeric Arrays?
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> I imagine it could use them just fine, using the generic=20
> Python sequence get item stuff, but that would be a whole lot=20
> lower performance than if it understood the Numeric API and=20
> could access the data array directly. Also, how does it deal=20
> with multiple dimension indexing ( array[3,6,2] ) which the=20
> standard python sequence types do not support?
>=20
> As I think about this, I think your suggestion is fabulous.=20
> Pyrex (or a
> Pyrex-like) language would be a fabulous way to write code=20
> for NumArray, if it really made use of the NumArray API.
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> Thanks for your input,
>=20
> -Chris
>=20
> --=20
> Christopher Barker, Ph.D.
> Oceanographer
>                                     	=09
> NOAA/OR&R/HAZMAT         (206) 526-6959   voice
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> Chr...@no...
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