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Re: Random access loops performing slowly
From: |
David Bateman |
Subject: |
Re: Random access loops performing slowly |
Date: |
Mon, 15 Oct 2007 10:16:04 +0200 |
User-agent: |
Thunderbird 1.5.0.7 (X11/20060921) |
Bhaskar Mehta wrote:
> Dear All,
> I have being doing some form of matrix factorization, where I iterate through
> all non zeros of a sparse matrix
> I use find/spfind to find all non zeros and then update two separate matrices
> with the found indices
>
> [i j vals]=find(Z);
> For k=1:length(i)
> ## access U(i(k),:):
> ## access V(j(k),: );
> end
>
> U, V are zeros(N,2), and zeros(M,2) respectively, where size(Z) is M x N.
>
>
> Such loops such *extremely* slowly: 10 seconds on a fast server vs 0.3
> seconds on a laptop with Matlab.
> When more than one access is made in a loop to U(i(k),:): ), the speed is
> even slower. I have provided an example of a loop which runs even slower.
>
> I additionally get an error with octave → “error: can't perform indexing
> operations for <unknown type> type”
>
> Can any wise guys help me with this? I would be much obliged.
> Best regards,
> Bhaskar
>
>
>
See the thread
http://www.nabble.com/Speedup-of-random-indesing-of-sparse-matrices-%28comparison-to-scilab%29-tf4595574.html#a13123915
I believe this issue is addressed in 2.9.15.. Please try that version
and report again. Unfortunately without the input file in your example I
can't test it to prove that it is fixed..
D.
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David Bateman address@hidden
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