[Octave-bug-tracker] [bug #36104] determinant of a sparse zero matrix

[Marco Caliari]

URL:
  <http://savannah.gnu.org/bugs/?36104>

                 Summary: determinant of a sparse zero matrix
                 Project: GNU Octave
            Submitted by: caliari
            Submitted on: Thu 05 Apr 2012 19:39:42 GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.6.0
        Operating System: GNU/Linux

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Details:

Dear all,

I found the following:


A=sparse(0);
B=sparse(zeros(0,1),zeros(0,1),1,1,1);
A==B
ans = Compressed Column Sparse (rows = 1, cols = 1, nnz = 1 [100%])

  (1, 1) ->  1
det(A)
ans = 0
det(B)
error: det: SparseMatrix::determinant symbolic factorization failed


So, A e B are equal, but it is not possible to compute the determinant of B.
The definition of B is weird, I know, but it is precisely what you get from


B = sprand(1,1,0);


This bug is present at least since 3.0.5. By the way, in Matlab A and B
coincides and have the same zero determinant.

Marco




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