[Octave-bug-tracker] [bug #47415] out of memory with factorized sparse matrix using mldivide

[Carlo de Falco]

Follow-up Comment #7, bug #47415 (project octave):

I also tried the following:

Octave 4.1+

>> [l, u, p] = lu (A);
>> issparse (p)
ans = 0
>> issparse (-p)
ans = 0
-verbaitim-

Matlab

>> [l, u, p] = lu (A);
>> issparse (-p)
ans =
     1
>> issparse (p) 
ans =
     1
-verbaitim-

this difference makes sense because AFAIK Matlab, unlike Octave
does not have a specific permutation matrix class, but should we also return
true for issparse when applied to a permutation (or diagonal) matrix? should
unary minus applied to a permutation matrix return a sparse rahter than full
matrix?



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