[Octave-bug-tracker] [bug #29770] Wrong determinat

[David Bateman]

Follow-up Comment #3, bug #29770 (project octave):

You are dealing with values in the matrix that are approximately 10, and so
an error of at least 10*eps or larger is to be expected, where eps is the
machine precision. For IEEE754 double precision 10*eps is 2.2204e-15 which is
very close to the error you are seeing. So really a rounding error of this
size is absolutely normal and correct.

Why the change between your versions of Octave 3.0.5 and 3.2.3 you asked. I
suspect you changed the version of LAPACK you used with Octave between the two
versions and the matrix factorisation used in calculating the determinant was
done slightly differently between the two cases. I suspect you used a generic
NETLIB lapack with 3.0.5 and an optimised ATLAS version with 3.2.3..

D.


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