Matt J
Posts:
4,996
Registered:
11/28/09


Re: speeding up ACCUMARRAY
Posted:
Nov 14, 2012 3:27 PM


"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. ==================
Precasting to uint32 does seem to help!
> 2) Sparse multiplication engine might benefice multithreading, and other lowlevel optimization. > > Accumarray is not slow. Just sparse is fast. ================
Seems like a false distinction to me. ;)

