[Octave-bug-tracker] [bug #43519] eigs really slow compared to Matlab

[John W. Eaton]

Follow-up Comment #6, bug #43519 (project octave):

Here is what I see:


octave:1> more off
octave:2> function doit (L)
>   a=rand(L)>0.95;
>   b=a+a'+0.001*eye(L);
>   c=sparse(b);
>   tic; e=eigs(b); toc
>   tic; e=eigs(c); toc 
> endfunction
octave:3> for L = 1:6
>   doit (L*1000)
> endfor
Elapsed time is 0.561315 seconds.
Elapsed time is 0.104919 seconds.
Elapsed time is 3.02288 seconds.
Elapsed time is 0.599574 seconds.
Elapsed time is 9.07814 seconds.
Elapsed time is 1.80241 seconds.
Elapsed time is 15.431 seconds.
Elapsed time is 3.10979 seconds.
Elapsed time is 29.1392 seconds.
Elapsed time is 5.99817 seconds.
Elapsed time is 50.4954 seconds.
Elapsed time is 9.98989 seconds.
octave:4> version
ans = 3.8.2


My system has 16GB of memory.

To see whether it is actually CPU time used or time spent by the system
swapping, I recommend using cputime instead of tic/toc since tic/toc measures
wall clock time, not CPU time used.

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