[Octave-bug-tracker] [bug #56232] Octave crash when inverting an empty sparse matrix.

[Marco Caliari]

Follow-up Comment #34, bug #56232 (project octave):

For a sparse singular matrix, it is not clear to me what matlab does:


>> inv(sparse([1,0;1,0]))
Warning: Matrix is singular to working precision. 

ans =

   (1,1)        1
   (2,1)     -Inf
   (2,2)      Inf
>> inv(sparse([1,2;0,0]))
Warning: Matrix is singular to working precision. 

ans =

   (1,1)      NaN
   (2,1)      NaN
   (1,2)     -Inf
   (2,2)      Inf


For the same examples, in the full form, matlab gives a matrix of Inf. The
same does octave. I would suggest that octave gives a sparse matrix of Inf.
There are five cases in which tinverse gives the division by zero error. It
should be enough to modify them in such a way that a sparse matrix of Inf is
returned.

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