Re: Very slow filter.cc

[David Bateman]

address@hidden wrote:

> Thanks for your comment, David,
>
> From: David Bateman <address@hidden>
>  
>
> > What was going to be my first step was to compile three different 
> > versions of octave.
> > These being 2.1.50, 2.1.57 and 2.1.64, which correspond to the last 
> > three testing releases. The first before NDArray's were integrated, the 
> > second when NDArray's were integrated, but the filter function wasn't 
> > changed to use them and the last with the filter function converted to 
> > NDArray's. Getting the times of the test case you propose for these 
> > three build, would really confirm your problem.
> >    
>
> I tried octave-2.1.50 and octave-2.1.57. It took the same time as
> octave-2.1.64. It means NDarray support in both filter.cc and octave
> is not the slowing factor, is it right?
>
> Also, I carefully compared filter.cc of octave-2.1.50 and
> octave-2.0.17. It seems there is no difference in filtering algorithm
> itself. I realized that the slow filter.cc comes from more essential
> part of octave-2.1.x.
>  
Hi Akira,

Then this indeed means that the NDArray support is not the cause of the 
problem. This might point to a deeper problem, but it is difficult to 
see what. It might also just be a problem with the time measurement 
under 2.0.17, or on your machine. Did you do a sanity check on the 
numbers? You measured 14.7 and 1.62 seconds. Are these the wall-times 
that these really took? you might also try

t = cputime; y = filter(b,1,x); cputime - t

rather than using tic/toc and see if there is better consistency between 
2.0.17 and the 2.1.x versions...

If the problem remains, the next step woul dbe to profile the two 
versions of octave to figure out what is taking the time. Though that is 
likely to take a lot of effort...

Regards
David



--
David Bateman                                address@hidden
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