Re: indexing expression performance

[Thomas Weber]

Am Donnerstag, den 15.01.2009, 13:57 +0100 schrieb Jaroslav Hajek:
> On Thu, Jan 15, 2009 at 1:48 PM, Francesco Potortì <address@hidden> wrote:
> > I had written:
> >>>Also, Francesco, I forgot to do the obvious thing and test your examples
> >>>with 3.1.51. At least on my machine, it looks like the performance has been
> >>>reversed by the latest dense indexing improvements.
> >>>
> >>>octave:1> kk=rand(156,222,1,44,8);
> >>>octave:2> t=cputime; for ii=1:44, for jj=1:8, mm=kk(:,:,:,ii,jj); endfor,
> >>>endfor, cputime-t
> >>>ans =  0.072004
> >>>octave:3> cp=[1,cumprod(size(kk)(1:end-1))]; len=156*222; t=cputime; for
> >>>ii=1:44, for jj=1:8,base=sum(([1,1,1,ii,jj]-1).*cp); 
> >>>mm=kk(base+1:base+len);
> >>>endfor, endfor, cputime-t
> >>>ans =  0.12401
> >>
> >>Wonderful!  This will make my code more readable as soon as I upgrade :)
> >
> > Hm.  I installed Octave 3.1.51 from Debian's "experimental" (I never got
> > round to finding the time to build Octave myself).  I use an amd64 box.
> > Unfortunately, I see no big difference with 3.0.1 :(
> >
> > The timings of the first test versus the second on my box are:
> > - 5.1s versus 0.30s with 3.0.1
> > - 5.2s versus 0.27s with 3.1.51
> >
> > So apparently I am not benefitting from the 3.1.51 dense indexing 
> > improvements.
> >
> 
> The dense indexing improvements started with
> http://hg.savannah.gnu.org/hgweb/octave/rev/7cbe01c21986
> dated 20th October and lots of bugfixes afterwards. I don't think this
> was in the 3.1.51 snapshot which I think was done in late July. There
> was no 3.1.52 so far. So, if you want these, development sources are
> your only resort.

I'd vote for a new snapshot. Or, if you can give me a mercurial id where
sources are in a reasonable[1] shape, we can use that for a new snapshot
package in Debian.

[1]  Reasonable by whatever metric you choose.

        Thomas