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[Octave-bug-tracker] [bug #29768] logm fix
From: |
Jaroslav Hajek |
Subject: |
[Octave-bug-tracker] [bug #29768] logm fix |
Date: |
Fri, 07 May 2010 10:19:46 +0000 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100317 SUSE/3.5.9-0.1.1 Firefox/3.5.9 |
Follow-up Comment #7, bug #29768 (project octave):
I removed the old unconditional error checks because Matlab doesn't seem to
do them either:
>> sqrtm([1 -1 -1; 0 1 -1; 0 1 -1])
ans =
1.0e+08 *
0.0000 1.0183 -1.0183
0 0.5092 -0.5092
0 0.5092 -0.5092
I believe the residual argument is intended to verify the result:
octave:1> [x,err] = sqrtm([1 -1 -1; 0 1 -1; 0 1 -1])
warning: sqrtm: matrix is singular, may not have a square root
x =
1.0000e+00 + 0.0000e+00i -3.0000e+00 - 1.3422e+08i 1.0000e+00 +
1.3422e+08i
0.0000e+00 + 0.0000e+00i 0.0000e+00 - 6.7109e+07i 0.0000e+00 +
6.7109e+07i
0.0000e+00 + 0.0000e+00i 0.0000e+00 - 6.7109e+07i 0.0000e+00 +
6.7109e+07i
err = 1.9640
isntead of computing the exact residual (which can be costly), Matlab also
allows estimating it using a special power method technique. Octave currently
can't.
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