[Octave-bug-tracker] [bug #60738] logm returning incorrect result with some real non-symmetric matrices

[Markus Mützel]

Follow-up Comment #7, bug #60738 (project octave):

Thanks for the patch. (Unfortunately, it didn't apply for me.)

I pushed the part of it that adds the tolerance to the check for real negative
values in a complex vector here:
https://hg.savannah.gnu.org/hgweb/octave/rev/fe06c183cc4e

Additionally, I pushed a patch that fixes e.g. `logm (zeros (3))` here:
https://hg.savannah.gnu.org/hgweb/octave/rev/4778b21b1386

I'm not sure about the impact of the other changes in your patch. Maybe those
should better go to the default branch?
I tried `logm(ones(3))` in Matlab and it gives a different result:

>> logm(ones(3))
Warning: Principal matrix logarithm is not defined for A with nonpositive real
eigenvalues. A non-principal matrix logarithm is returned. 
> In logm (line 63) 

ans =

-24.713572198920126 + 2.094395102393196i   13.566584297695865 -
1.047197551196598i   12.245600189892365 - 1.047197551196598i
 13.566584297695865 - 1.047197551196598i  -24.713572198920119 +
2.094395102393195i   12.245600189892361 - 1.047197551196597i
 12.245600189892365 - 1.047197551196598i   12.245600189892361 -
1.047197551196597i  -23.392588091116618 + 2.094395102393195i


I don't know if one or the other is "more correct" though.


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