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To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Python CPU
Date: Mon, 04 Apr 2011 14:58:20 -0400
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On 4/4/2011 1:14 PM, Terry Reedy wrote:
> On 4/4/2011 5:23 AM, Paul Rubin wrote:
>> Gregory Ewing<greg.ewing@canterbury.ac.nz> writes:
>>> What might help more is having bytecodes that operate on
>>> arrays of unboxed types -- numpy acceleration in hardware.
>>
>> That is an interesting idea as an array or functools module patch.
>> Basically a way to map or fold arbitrary functions over arrays, with a
>> few obvious optimizations to avoid refcount churning. It could have
>> helped with a number of things I've done over the years.
>
> For map, I presume you are thinking of an array.map(func) in system code
> (C for CPython) equivalent to
>
> def map(self,func):
> for i,ob in enumerate(self):
> self[i] = func(ob)
>
> The question is whether it would be enough faster. Of course, what would
> really be needed for speed are wrapped system-coded funcs that map would
> recognize and pass and received unboxed array units to and from. At that
> point, we just about invented 1-D numpy ;-).
>
> I have always thought the array was underutilized, but I see now that it
> only offers Python code space saving at a cost of interconversion time.
> To be really useful, arrays of unboxed data, like strings and bytes,
> need system-coded functions that directly operate on the unboxed data,
> like strings and bytes have. Array comes with a few, but very few,
> generic sequence methods, like .count(x) (a special-case of reduction).

After posting this, I realized that ctypes makes it easy to find and 
wrap functions in a shared library as a Python object (possibly with 
parameter annotations) that could be passed to array.map, etc. No 
swigging needed, which is harder than writing simple C functions. So a 
small extension to array with .map, .filter, .reduce, and a wrapper 
class would be more useful than I thought.


-- 
Terry Jan Reedy