[Octave-bug-tracker] [bug #61689] inv of scalar emits a singular matrix warning

[A.R. Burgers]

Follow-up Comment #1, bug #61689 (project octave):

same result for:


octave:1> inv(diag(2))
warning: matrix singular to machine precision
ans = 0.5000


Consistent with that comments in the source code indicate scalars are treated
as diagonal matrices in this context.

The problem I think is in this bit in liboctave/array/dMatrix.cc around line
644 where the rcon argument is not adjusted


  if (typ == MatrixType::Diagonal)  // a scalar is also classified as
Diagonal.
    ret = 1 / (*this);


rcon is left at the 0 initial value set in libinterp/corefcn/inv.cc around
line 81. m.inverse is called at line 170 in inv.cc

Then later in inv.cc rcond_plus_one_eq_one will be true, and the warning will
be triggered.


rcond_plus_one_eq_one = xrcond + 1.0 == 1.0;



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