From help-octave-request at bevo dot che dot wisc dot edu Sat Jan 17 18:55:50 2004
Subject: Re: Octave and threaded ATLAS and FFTW
From: "Henry F. Mollet" <mollet at pacbell dot net>
To: "Dmitri A. Sergatskov" <dmitri at unm dot edu>,    "John W. Eaton" <jwe@bevo.che.wisc.edu>
CC: Octave_post <help-octave at bevo dot che dot wisc dot edu>
Date: Sat, 17 Jan 2004 16:52:21 -0800

With a 400 Mhz Power PC G3 the two items tested take considerably longer. I
can understand a factor of 2000/400 = 5. Not that I need the speed, but does
it imply that vecLib (with BLAS and LAPACk) in Mac OS X Dev Tools is about
4-10 times slower compared to  ATLAS 2.6.0?
Henry

octave:1> tic; t1=cputime ; a=rand(2000); t2=cputime ; toc
ans = 5.0177
octave:2> t2-t1
ans = 3.1200 % ca. 20 times longer
octave:3> tic; t1=cputime ; b=inv(a); t2=cputime ; toc
ans = 87.499
octave:4> t2-t1
ans = 72.130 % ca. 39 times longer


on 1/16/04 4:03 PM, Dmitri A. Sergatskov at dmitri at unm dot edu wrote:

> John W. Eaton wrote:
> 
>> I think it would be worth an attempt just to see what happens, but I
>> don't have time (or the need) to do it myself.  If you do it, please
>> post your results to the list.
> 
> I did compile octave 2.1.50 with pthreaded atlas. Though it mostly work
> and some benchmarks show improvements. E.g. from (in)famous Octave2 benchmark
> (which was discussed on octave-maint. list)
> 
> "normal" ATLAS:
> 700x700 cross-product matrix (b = a' * a)___________ (sec): 0.2713
> 
> "pthreded" ATLAS
> 
> 700x700 cross-product matrix (b = a' * a)___________ (sec): 0.1727
> 
> I am not quite sure yet those are real numbers since I discovered that
> "cputime" does not work as expected any more (at least not as I expected):
> 
> octave:2> tic; t1=cputime ; a=rand(2000); t2=cputime ; toc
> ans = 0.16871
> octave:3> t2-t1
> ans = 0.16000
> (That is probably close enough)
> 
> octave:4> tic; t1=cputime ; b=inv(a); t2=cputime ; toc
> ans = 7.3011
> octave:5> t2-t1
> ans = 1.8600
> (7.3 seems more real here)
> 
> octave:9> tic; t1=cputime ; c=b*a; t2=cputime ; toc
> ans = 2.9955
> octave:10> t2-t1
> ans = 0
> (Well...)
> 
> octave:12> tic; t1=cputime ; ifft(fft(a)); t2=cputime ; toc
> ans = 1.5286
> octave:13> t2-t1
> ans = 1.5000
> 
> (Looks OK again)
> 
> So all BLAS/LAPACK benchmarks which use "cputime" are greatly improved :)
> (Octave2 uses tic; toc method.)
> 
> Frankly, by reading ATLAS docs, I do not understand why would I get any
> improvements
> since ATLAS by itself will not spawn separate tasks...
> 
>> Thanks,
>> 
>> jwe
> 
> Sincerely,
> Dmitri.
> 
> p.s.
> 
> The tests done on AthlonMPx2 2000 MHz. Octave2 is from
> http://www.sciviews.org/other/benchmark.htm
> ATLAS 2.6.0 which I compiled myself.
> 
> 
> 
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