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[Octave-bug-tracker] [bug #45944] eig(X, 'nobalance') does not exist in
From: |
Nir Krakauer |
Subject: |
[Octave-bug-tracker] [bug #45944] eig(X, 'nobalance') does not exist in Octave vs. Matlab |
Date: |
Sun, 7 Mar 2021 12:16:35 -0500 (EST) |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:86.0) Gecko/20100101 Firefox/86.0 |
Follow-up Comment #4, bug #45944 (project octave):
You can try looking at [1], which gives some examples (involving larger
matrices) where balancing influences the answer noticeably.
Also, Octave's current eig function [2] has a test case where balancing
changes the answer (albeit probably only by something on the order of roundoff
error):
## "balance" is always default
## so the results with and without "balance" should be the same
## while in this case "nobalance" should produce different result
%!test
%! A = [3 -2 -0.9 0; -2 4 1 -0; -0 0 -1 0; -0.5 -0.5 0.1 1];
%! [V1, D1] = eig (A);
%! [V2, D2] = eig (A, "balance");
%! [V3, D3] = eig (A, "nobalance");
%! assert (V1, V2)
%! assert (D1, D2)
%! assert (isequal (V2, V3), false)
[1] http://www.sci.wsu.edu/math/faculty/watkins/pdfiles/balbad.pdf
[2] https://hg.savannah.gnu.org/hgweb/octave/file/tip/libinterp/corefcn/eig.cc
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