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Re: A faster sum
From: |
Victor Eijkhout |
Subject: |
Re: A faster sum |
Date: |
Sat, 21 May 2005 16:33:30 -0400 |
On May 21, 2005, at 4:19 PM, Keith Goodman wrote:
So does it make sense to modify the built-in function sum to use
matrix multiplication?
I wouldn't do it.
I'm still a bit surprised. The multiplication approach takes twice as
many operations, but it's probably faster because it uses Atlas, which
tries to optimize use of bandwidth, cache lines, number of registers
&c. Since the memory behaviour is more important than the actual
efficiency of operations (to a degree), I guess the Atlas matrix-vector
multiply will be more efficient.
However, this depends on all sorts of assumptions about architecture.
I'd leave the code the way it is, and preserve this as a bit of 'octave
folklore'.
V.
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-------------------------------------------------------------
- A faster sum, Keith Goodman, 2005/05/21
- Re: A faster sum, Victor Eijkhout, 2005/05/21
- Re: A faster sum, Keith Goodman, 2005/05/21
- Re: A faster sum, Mike Miller, 2005/05/21
- Re: A faster sum, Victor Eijkhout, 2005/05/21
- Re: A faster sum, Keith Goodman, 2005/05/21
- Re: A faster sum,
Victor Eijkhout <=
- Re: A faster sum, Mike Miller, 2005/05/21
- Re: A faster sum, John W. Eaton, 2005/05/21