[Octave-bug-tracker] [bug #43875] warning: matrix singular to machine precision for triangular matrices

[Rik]

Follow-up Comment #3, bug #43875 (project octave):

Seems to work, although there is one oddity.  The warning about the matrix
being singular is printed out just once for the initial matrix A.  Subsequent
left divisions do not produce another warning.  On the other hand, every left
division of the U matrix produces a warning.  This is probably something to do
with the matrix type caching.


octave:1> A = [1,2,3;4,5,6;7,8,9];
octave:2> A \ ones (3,1);
warning: matrix singular to machine precision, rcond = 1.54198e-18
octave:3> A \ ones (3,1);
octave:4> A \ ones (3,1);
octave:5> [L,U] = lu (A);
octave:6> U \ ones (3,1);
warning: matrix singular to machine precision, rcond = 2.59052e-18
octave:7> U \ ones (3,1);
warning: matrix singular to machine precision, rcond = 2.59052e-18
octave:8> U \ ones (3,1);
warning: matrix singular to machine precision, rcond = 2.59052e-18




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