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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: 4,997
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$isp$>...
> "Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <k7vfli$da4$>...
> > "Matt J" wrote in message <k7ulhl$iod$>...
> >

> > >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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