FW: [Numpy-discussion] Speeding up numarray -- questions on its design
perry at stsci.edu
Tue Jan 25 19:52:09 CST 2005
Hmmm, it looks like it was sent only to Chris. My mistake. -- Perry
From: Perry Greenfield [mailto:perry at stsci.edu]
Sent: Tuesday, January 18, 2005 5:58 PM
To: Chris Barker
Cc: Perry Greenfield
Subject: Re: [Numpy-discussion] Speeding up numarray -- questions on its
On Jan 18, 2005, at 12:43 PM, Chris Barker wrote:
> Hi all,
> This discussion has brought up a question I have had for a while:
> Can anyone provide a one-paragraph description of what numarray does
> that gives it better large-array performance than Numeric?
It has two aspects: one is speed, but for us it was more about memory.
It is likely faster (for simpler cases, i.e., ones that don't involve
strides, byteswaps or type conversions) because the C code for the loop
is as simple as can be resulting in better optimizations. But we
haven't done careful research on that. It has a number of aspects that
lessen memory demands:
1) fewer temporaries created, particularly for type conversions.
2) avoids the memory wasting scalar type coercions that Numeric has.
3) allows use of memory mapping. This one is at the moment not a strong
advantage due to the fact that the current limit is due to Python.
Interesting large arrays sizes are bumping into the Python limit making
this less useful. But when this goes away (this year I hope) it is
again a useful tool for minimizing memory demands.
There are other advantages, but these are the primary ones that relate
to large array performance that I recall offhand (Todd may recall
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