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Re: new snapshot?
From: |
John W. Eaton |
Subject: |
Re: new snapshot? |
Date: |
Fri, 26 Feb 2010 06:01:20 -0500 |
On 26-Feb-2010, Michael D. Godfrey wrote:
| I built the current system on Fedora 12 x86_64 with default
| settings and got only one test failure:
|
| >>>>> processing /data/d/src/octave/hg/octave/scripts/sparse/svds.m
| ***** testif HAVE_ARPACK
| [u2,s2,v2,flag] = svds(a,k,0);
| s2 = diag(s2);
| assert(flag,!1);
| assert(s(k:-1:1), s2, 1e-10);
| !!!!! test failed
| assert (s (k:-1:1),s2,1e-10) expected
| 38.060
| 38.060
| 38.034
| 38.034
| 38.015
| 38.015
| 38.004
| but got
| 38.060
| 38.034
| 38.034
| 38.015
| 38.015
| 38.004
| 38.004
| maximum absolute error 0.0263523 exceeds tolerance 1e-10
| The version of arpack is: arpack-2.1-12.fc12.x86_64
| Looks like an indexing error.
It could be. Here's what I know. The test calls svds. The call to
svds in eigs is sometimes returning
s =
0.95151
0.95085
0.95085
0.95038
0.95038
0.95009
0.95009
-0.95009
-0.95009
-0.95038
-0.95038
-0.95085
-0.95085
-0.95151
(apparently this is the result we expect) but sometimes it is
returning
s =
0.95085
0.95085
0.95038
0.95038
0.95009
0.95009
-0.95009
-0.95009
-0.95038
-0.95038
-0.95085
-0.95085
-0.95151
-0.95151
and other times it is returning
s =
0.95151
0.95151
0.95085
0.95085
0.95038
0.95038
0.95009
0.95009
-0.95009
-0.95009
-0.95038
-0.95038
-0.95085
-0.95085
A slightly simpler test script that should demonstrate this problem
directly without needing svds is
z = sparse (100, 100);
d = repmat (1/40, [1, 98]);
b = sparse (eye (100) + diag (d, 2) + diag (d, -2));
m = [z, b; b', z];
b_sigma = sparse (1, 1);
b_opts.tol = sparse (1, 1, 1e-10/40/sqrt(2));
b_opts.disp = 0;
b_opts.maxit = 300;
[V, s, flag] = eigs (m, 14, b_sigma, b_opts);
s = diag (s)
That's as far as I've been able to get so far. I don't know whether
the problem is in the way we are using arpack to compute he
eigenvalues, or if it is in arpack itself.
jwe
- new snapshot?, (continued)
- new snapshot?, John W. Eaton, 2010/02/18
- Re: new snapshot?, Jaroslav Hajek, 2010/02/18
- Re: new snapshot?, John W. Eaton, 2010/02/18
- Re: new snapshot?, David Bateman, 2010/02/18
- Re: new snapshot?, John W. Eaton, 2010/02/24
- Re: new snapshot?, Jaroslav Hajek, 2010/02/25
- Re: new snapshot?, John W. Eaton, 2010/02/25
- Re: new snapshot?, John W. Eaton, 2010/02/25
- Re: new snapshot?, Søren Hauberg, 2010/02/25
- Re: new snapshot?, Michael D. Godfrey, 2010/02/26
- Re: new snapshot?,
John W. Eaton <=
- Re: new snapshot?, Michael D. Godfrey, 2010/02/26
- Re: new snapshot?, Jaroslav Hajek, 2010/02/26
- Re: new snapshot?, Michael D. Godfrey, 2010/02/26
- Re: new snapshot?, John W. Eaton, 2010/02/26
- Re: new snapshot?, Michael D. Godfrey, 2010/02/26
- Re: new snapshot?, Michael D. Godfrey, 2010/02/26
- Re: new snapshot?, Michael D. Godfrey, 2010/02/26
- Re: new snapshot?, David Bateman, 2010/02/28
- Re: new snapshot?, Michael D. Godfrey, 2010/02/28
Re: new snapshot?, Benjamin Lindner, 2010/02/18