compound operators

[Fredrik Lingvall]

Jaroslav Hajek wrote:
> Another changeset uploaded; the symmetric cases A'*A, A*A', A.'*A and
> A*A.' are now mapped to xSYRK and ZHERK. With these, the benchmark
> becomes more impressive:
>
> n = 50; m = 505000; a = rand(m,n); tic; c = a'*a; toc; clear
>
> with current Octave:
>
> Elapsed time is 4.24332 seconds.
>
> with the new changeset:
>
> Elapsed time is 0.916971 seconds.
>
> i.e. a 462% speed-up (this is, of course, caused by the fact that
> DSYRK not only avoids transposing and operates more cache coherently,
> just like DGEMM('T','N',...), but also calculates only half of the
> matrix)
>   

Super! I have been waiting for this one - no more need for my 
specialized oct-functions to do this.

/Fredrik

-- 
Fredrik Lingvall, PhD                                                              
E-mail: fl at ifi.uio.no, fredrik.lingvall at gmail.com
Web:    http://folk.uio.no/fl/