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[Octave-bug-tracker] [bug #63384] Error for "inv(NaN)" with LAPACK 3.11.


From: Markus Mützel
Subject: [Octave-bug-tracker] [bug #63384] Error for "inv(NaN)" with LAPACK 3.11.0
Date: Mon, 21 Nov 2022 08:57:25 -0500 (EST)

Follow-up Comment #22, bug #63384 (project octave):

Maybe, this is caused by "rcond" now being returned as 0 (instead of NaN)
together with this in our code:

      if ((calc_cond || mattype.ishermitian ()) && rcon == 0.0)
        ret = Matrix (rows (), columns (),
                      octave::numeric_limits<double>::Inf ());


The documentation for dgecon says about rcond:
https://netlib.org/lapack/explore-html/dd/d9a/group__double_g_ecomputational_ga188b8d30443d14b1a3f7f8331d87ae60.html
>           RCOND is DOUBLE PRECISION
>           The reciprocal of the condition number of the matrix A,
>           computed as RCOND = 1/(norm(A) * norm(inv(A))).

So, rcond *should* be NaN in this case if I understand correctly...



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