Matt J
Posts:
4,976
Registered:
11/28/09
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Re: speeding up ACCUMARRAY
Posted:
Nov 14, 2012 3:27 PM
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"Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <k80spd$ra8$1@newscl01ah.mathworks.com>...
> "Matt J" wrote in message <k80l22$qd5$1@newscl01ah.mathworks.com>...
>
> >
> > Anyway, my point remains. Sparse matrix multiplication has to perform multiplications with the x(j) somewhere, whereas accumarray, in my tests, does not. So sparse mult. is further handicapped.
>
> 1) Sparse internally access memory via integer indexing. Your accumarray has to cast doubles (firs input) to integers.
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Precasting to uint32 does seem to help!
> 2) Sparse multiplication engine might benefice multi-threading, and other low-level optimization.
>
> Accumarray is not slow. Just sparse is fast.
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Seems like a false distinction to me. ;)
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