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[Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK ge
From: |
Dan Sebald |
Subject: |
[Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN |
Date: |
Fri, 20 Apr 2018 13:23:25 -0400 (EDT) |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:59.0) Gecko/20100101 Firefox/59.0 |
Follow-up Comment #19, bug #53700 (project octave):
At first I thought there was something wrong about the system setup, i.e.,
this large matrix with numbers much larger than eye() caused an instability
somewhere. However, experimenting a bit, I don't quite understand what is
happening with the number of eigenvalues. Going back to the original test:
octave:2> A = magic (100) / 10 + eye (100);
octave:3> opts.v0 = (1:100)';
octave:4> opts.maxit = 10;
octave:5> d = eigs (A, 10, "sm", opts);
warning: eigs: Only 1 of the 10 requested eigenvalues converged
warning: called from
eigs at line 265 column 18
octave:6> d(d==d)
ans = 1.00000
However, change the requested number of eigenvalues from 10 to 100, i.e., all
the eigenvalues and surprisingly there is no convergence problem:
octave:7> d = eigs (A, 100, "sm", opts);
octave:8> d(d==d)
ans =
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 - 0.00000i
1.00000 + 0.00000i
1.00000 + 0.00000i
-2885.60700 + 0.00000i
2887.60700 + 0.00000i
50006.00000 + 0.00000i
Doing sum(A), every value is 50006, and it probably isn't a coincidence that
the last eigenvalue in the list is 50006. Seems reasonable.
So I'm confused. Why when we request less eigenvalues do we have a less
robust situation? Typically when one puts a restriction on an algorithm it
leads to improved robustness...say if we know some eigenvalues are problematic
we might choose sigma and the number of eigenvalues in a way that squeezes
those problematic eigenvalues out of the picture.
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- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, (continued)
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Mike Miller, 2018/04/19
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Mike Miller, 2018/04/19
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Mike Miller, 2018/04/19
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Mike Miller, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Marco Caliari, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Marco Caliari, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Mike Miller, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN,
Dan Sebald <=
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dmitri A. Sergatskov, 2018/04/20
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/22
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dmitri A. Sergatskov, 2018/04/22
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Marco Caliari, 2018/04/23
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/23
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Marco Caliari, 2018/04/23
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Dan Sebald, 2018/04/23
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, Rik, 2018/04/24
- [Octave-bug-tracker] [bug #53700] eigs test failure related to ARPACK generating real NaN rather than complex NaN+1i*NaN, John W. Eaton, 2018/04/24