Re: benchmarks - sort

[David Bateman]

Well, for the hell of it I programmed a simple sort oct-file to test 
what would be faster (IEEE754 integer compare or floating point compare
with checking for Inf and NaN), you can check the attached oct-file.
One complication of IEEE754 is the symmetry of negative and postive numbers.
This means that positive and negative tests need to be treated seperately, as
opposed to a 2's complement respresentation 

The code at the moment is only for a row vector and is attached the example
I used was

a=randn(1,100000); a(1) = NaN; a(2) = -Inf; a(3) = Inf; tic; mysort(a); t = 
toc; tic; mysort(a,1); t1= toc; t, t1

And I got the result

t = 0.27054
t1 = 0.23212

showing that IEEE754 integer compares are about 20% faster....  Well
IEEE754 is faster, but it is certainly not a factor of 10 faster...
Seems like we need to look elsewhere for this order of magnitude
increase...

Regards
D.


According to Schloegl Alois <address@hidden> (on 01/06/04):
> Zitat von Paul Kienzle <address@hidden>:
> 
> >
> > Paul Thomas pointed me to these benchmarks.  Anybody want to do
> > something about them?
> >
> >     http://www.sciviews.org/other/benchmark.htm
> >
> 
> ...
> 
> >
> > I.C Matlab 0.89  - Octave 7.77
> >      b = sort(a);
> >
> > Octave's sort is surprisingly slow.  3x worse than any other package
> > mentioned.  Anyone know a fast stable sort algorithm?
> >
> 
> 
> One reason, for the bad performance of the sort algorithm might be the 
> exception
> handling of NaNs. See also
> http://www.octave.org/octave-lists/archive/bug-octave.2001/msg00047.html
> 
> Sorting on the binary level might be helpful, because the bit patterns of the
> IEEE754 numbers provide the correct sorting order. This is
> -inf < -1 < 0 < 1 < inf < NaN
> 
> Just my few thougths.
> 
> 
> Alois
> 

-- 
David Bateman                                address@hidden
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mysort.cc
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