[Octave-bug-tracker] [bug #47415] out of memory negating a permutation matrix

[Rik]

Follow-up Comment #12, bug #47415 (project octave):

Answering an earlier question: Matlab does not distinguish between 0 and -0
and stores everything as +0.  Octave, for full matrices, does have both +0 and
-0.  Sparse matrices, however, only store +0.

In my view, sparse, permutation, and diagonal matrices are all closer to each
other than they are to full matrices.  Ergo, I also believe that permutation
matrices should behave more like sparse matrices under negation.  In this
case, -P should only negate the non-zero elements of P.  If we're looking for
consistency, this is already what Diagonal matrices do.


z = diag ([1 2 3])
z =

Diagonal Matrix

   1   0   0
   0   2   0
   0   0   3

octave:11> z2 = -z
z2 =

Diagonal Matrix

  -1   0   0
   0  -2   0
   0   0  -3




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