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Re: fastest way to element-by-element multiply matix by vector?
From: |
David Bateman |
Subject: |
Re: fastest way to element-by-element multiply matix by vector? |
Date: |
Wed, 20 Jun 2007 09:47:36 +0200 |
User-agent: |
Thunderbird 1.5.0.7 (X11/20060921) |
Michael Creel wrote:
>
> Thanks for the script! The results (second run), with Octave 2.9.12 on
> AMD 64 X2 CPU @2000MHz running 64 bit Kubuntu 7.04 are:
> ( n, k) A.*repmat(b,1,k) diag(b)*A spdiag(b)*A
> ( 100, 100) 0.0180 s 0.0010 s 0.0060 s
> ( 100, 200) 0.0010 s 0.0020 s 0.0010 s
> ( 100, 500) 0.0030 s 0.0040 s 0.0020 s
> ( 100,1000) 0.0030 s 0.0080 s 0.0040 s
> ( 100,2000) 0.0060 s 0.0150 s 0.0080 s
> ( 200, 100) 0.0010 s 0.0040 s 0.0010 s
> ( 200, 200) 0.0020 s 0.0060 s 0.0020 s
> ( 200, 500) 0.0030 s 0.0140 s 0.0040 s
> ( 200,1000) 0.0060 s 0.0260 s 0.0070 s
> ( 200,2000) 0.0120 s 0.0520 s 0.0150 s
> ( 500, 100) 0.0010 s 0.0200 s 0.0020 s
> ( 500, 200) 0.0030 s 0.0360 s 0.0040 s
> ( 500, 500) 0.0070 s 0.0830 s 0.0110 s
> ( 500,1000) 0.0140 s 0.1620 s 0.0190 s
> ( 500,2000) 0.0290 s 0.3160 s 0.0410 s
> (1000, 100) 0.0030 s 0.0760 s 0.0030 s
> (1000, 200) 0.0060 s 0.1350 s 0.0080 s
> (1000, 500) 0.0130 s 0.3150 s 0.0180 s
> (1000,1000) 0.0240 s 0.6129 s 0.0370 s
> (1000,2000) 0.0570 s 1.1948 s 0.0820 s
> (2000, 100) 0.0060 s 0.3080 s 0.0090 s
> (2000, 200) 0.0120 s 0.5599 s 0.0160 s
> (2000, 500) 0.0240 s 1.2648 s 0.0370 s
> (2000,1000) 0.0460 s 2.4296 s 0.0750 s
> (2000,2000) 0.1090 s 4.8293 s 0.1670 s
> octave:3>
>
> To my taste, the first option wins, though the third is competitive.
> Thanks again, M.
>
I get the reverse and the third option wins.. The third option also has
a big memory advantage for large matrices..
D.
--
David Bateman address@hidden
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Re: fastest way to element-by-element multiply matix by vector?, Benjamin Lindner, 2007/06/20