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[Octave-bug-tracker] [bug #53258] test pcg.m fail
From: |
Rik |
Subject: |
[Octave-bug-tracker] [bug #53258] test pcg.m fail |
Date: |
Thu, 8 Mar 2018 07:53:42 -0500 (EST) |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) Gecko/20100101 Firefox/55.0 |
Follow-up Comment #10, bug #53258 (project octave):
I like Carlo's and Cristiano's idea to take this up at OctConf 2018.
I did make a lot of changes, but the big one that was necessary to resolve
this report was to change what the BIST tests were looking for. See the small
diff below
%! ## solve small diagonal system
%!
%! N = 10;
-%! A = diag ([1:N]); b = rand (N, 1);
-%! X = A \ b; # X is the true solution
-%! [x, flag] = pcg (A, b, [], N+1);
-%! assert (norm (x - X) / norm (X), 0, 1e-10);
+%! A = diag ([1:N]);
+%! b = rand (N, 1);
+%! [x, flag] = pcg (A, b, [], 2*N);
+%! assert (norm (A*x - b) / norm (b), 0, 1e-6);
In the original, the relative error in the solution X is checked. But the pcg
algorithm doesn't guarantee any such results so there were occasional failures
in the BIST tests.
In the modified version, I look at the residuals (Ax - b) normalized by the
magnitude of b [/ norm (b)]. This is the stopping criteria used by pcg itself
so as long as flag==0 the tolerance of 1e-6 will have been met.
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- [Octave-bug-tracker] [bug #53258] test pcg.m fail, (continued)
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Dmitri A. Sergatskov, 2018/03/02
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/06
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/07
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/07
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Dmitri A. Sergatskov, 2018/03/07
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Dmitri A. Sergatskov, 2018/03/07
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Cristiano Dorigo, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail,
Rik <=
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Carlo de Falco, 2018/03/08
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Marco Caliari, 2018/03/09
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Marco Caliari, 2018/03/09
- [Octave-bug-tracker] [bug #53258] test pcg.m fail, Rik, 2018/03/09