You are asked by the Posting Guide to provide a reproducible example and to post in plain text (because HTML gets mangled). I would guess your problem has nothing to do with multiplication, but without the code there is no way to say for sure. -- Sent from my phone. Please excuse my brevity.
On January 26, 2017 2:21:07 PM PST, ken eagle <eaglek2...@gmail.com> wrote: >Hi all. A question about performance of matrix multiplication. > > > >I have two relatively large matrices: > > > >A is 100x3072, all integers 0-255, not sparse > >B is 1016x3072, all integers 0-255, not sparse > > > >The command z<-B %*% t(A) works fine and takes roughly 0.2 seconds . >If I >add one row to B, the same command takes 2.4 seconds; at 1050 rows in >B, >the command is up to almost 4 seconds. Just trying to understand why >the >big slowdown is occurring, especially since the matrices I actually >want to >multiply have 1000 and 5000 rows, not 100 and 1017. > > > >Thanks, > >Ken > > > >(Macbook Pro running 10.11.6, 16Gb, R v 3.3.1) > > [[alternative HTML version deleted]] > >______________________________________________ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
