[Octave-bug-tracker] [bug #55885] Wrong sparse LU permutation matrix with vector option

[Rik]

Update of bug #55885 (project octave):

                  Status:                    None => Works For Me           

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Follow-up Comment #1:

According to the documentation, when called with 4-outputs


[L, U, P, Q] = lu (S)


the resulting decomposition is


P*S*Q = L*U


When called with the "vector" argument, the resulting decomposition is


S(P,Q) = L*U


So to test, I should have


S(P,Q) - L*U = 0



octave:25> S = sprand (5,5,0.3);
octave:26> [L,U,P,Q] = lu (S, 'vector');
octave:27> S(P,Q) - L*U
ans =

Compressed Column Sparse (rows = 5, cols = 5, nnz = 0 [0%])


So this looks correct to me.

For the second point, it makes no difference for indexing whether the vectors
are row or column vectors.


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