[Octave-bug-tracker] [bug #41441] Broadcasting does not behave properly on sparse matrices

[David Spies]

URL:
  <http://savannah.gnu.org/bugs/?41441>

                 Summary: Broadcasting does not behave properly on sparse
matrices
                 Project: GNU Octave
            Submitted by: dspyz
            Submitted on: Mon 03 Feb 2014 03:15:29 AM GMT
                Category: Octave Function
                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: dev
        Operating System: Any

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Details:

Broadcasting doesn't work at all for sparse matrices.  There appears to be no
good workaround

#Doesn't work automatically for sparse matrix with full vector
octave:1> a = sprand(100000,100000,0.00001);
octave:2> b = rand(100000,1);
octave:3> res = a == b;
error: mx_el_eq: nonconformant arguments (op1 is 100000x100000, op2 is
100000x1)

#Doesn't work explicitly for sparse matrix with full vector
octave:9> res = bsxfun(@eq,a,b);
error: out of memory or dimension too large for Octave's index type

#Doesn't work automatically for sparse matrix with sparse vector
octave:9> b = sparse(b);
octave:10> res = a == b;
error: mx_el_eq: nonconformant arguments (op1 is 100000x100000, op2 is
100000x1)

#Doesn't work explicitly for sparse matrix with sparse vector
octave:10> res = bsxfun(@eq,a,b);
error: out of memory or dimension too large for Octave's index type

#Often there's a special-case work-around, but it's generally unwieldy

octave:10> b_mat = diag(b) * spones(a);
octave:11> [i,j] = find(a);
octave:12> res = sparse(i,j,nonzeros(a) == nonzeros(b_mat));





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