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Topic: speeding up ACCUMARRAY
Replies: 12   Last Post: Nov 15, 2012 3:35 AM

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Matt J

Posts: 4,996
Registered: 11/28/09
Re: speeding up ACCUMARRAY
Posted: Nov 14, 2012 12:40 PM
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"Matt J" wrote in message <k80bi9$isp$1@newscl01ah.mathworks.com>...
> "Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <k7vfli$da4$1@newscl01ah.mathworks.com>...
> > "Matt J" wrote in message <k7ulhl$iod$1@newscl01ah.mathworks.com>...
> >

> > >In fact, the sparse matrix multiplication is probably even handicapped relative to accumarray, since it has to search through x for the appropriate x(J),
> >
> > There is no such step in sparse multiplication.

> =============
>
> Meaning that y=A*x is generated by looping over columns of A instead of rows? Even if so, how would that explain the speed difference?

================

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.



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