[Octave-bug-tracker] [bug #40712] Running into index errors with large, 64k square sparse matrices

[Paul Jakma]

URL:
  <http://savannah.gnu.org/bugs/?40712>

                 Summary: Running into index errors with large, 64k square
sparse matrices
                 Project: GNU Octave
            Submitted by: paul
            Submitted on: Tue 26 Nov 2013 16:56:38 GMT
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.6.3
        Operating System: GNU/Linux

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Details:

I have a 64k × 64 matrix, sparse matrix:

spstats(D)
ans =
  Compressed Column Sparse (rows = 1, cols = 64000, nnz = 15892 [25%])
...

I wanted to calculate D^-0.5, however it gives this error:

D = D**-0.5

error: memory exhausted or requested size too large for range of Octave's
index type -- trying to return to prompt

It was suggested to me to on #octave use:

 D(D>0) .^= -0.5

However, this gives the same error. In the end, the following workaround was
found, which does work:

Ds = diag(D);
Ds(Ds > 0) .^= -0.5;
Ds = diag(Ds);

It would be good though if the first 2 ways above worked too. 

While my matrices at the moment are 64k in size, they are likely to grow. They
are actually large graphs, in a 32bit node space. The 64k size will grow and
grow over time. Octave has been extremely useful in helping to analyse these
graphs. It'd be very useful to me if Octave's index type could support
operations on them.





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