Re: svds test failure

[Rik]

On 07/31/2012 07:02 AM, address@hidden wrote:
>
> No, you're not. There issue is that svds has a test that is
> nondeterministic and sometimes the error is higher than tolerance. One
> the machine that failed, try running "test svds" a few times and see
> how often that fails.
>
> I don't know if we can make this test nondeterministic because the
> randomness comes from ARPACK, not from Octave, so I don't know if we
> can seed it. We could just increase the tolerance.
7/31/12

Melvin,

This issue comes up again and again.  The issue is that ARPACK is an
iterative solution solver and the success or failure can depend on the
initial starting point relative to the solution.  In order to stop
variability in tests, we initialize Octave's random number generators and
then create an initial seed location (which is now always the same) to pass
to ARPACK.  However, even this hasn't fully stopped all failures.  It is
possible that this is due to small machine-dependent round-off errors which
render even the initial seed location slightly different between machines.

I am willing to try one more time on this issue.  I'm attaching a small
patch for svds.m.  Apply it with 'patch -p1 < svds.patch'.  At a shell do
'./run-octave' and try this code:

for i = 1:300
  bm(i) = test ("svds");
endfor
sum (bm)

If the sum is not exactly 300 then some test runs failed and I will be
completely out of ideas.

--Rik

svds.patch
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