On 31 Aug 2009, at 21:53, David Bateman wrote:

`Yes, but the configuration of SuiteSparse in terms of the pivot
``threshold is the default that TIm Davis sets for Octave and whatever
``mathworks chose to use for matlab. So don't expect exactly the behavior.
`

I see...

In Octave what does
matrix_type(A)
give?

>> matrix_type (A)
ans = Positive Definite
>>

`If it doesn't flag your matrix as PD then there might be an issue
``with the detection of the matrix and PD and the solver used in Octave
``will be LU.
`

on the other hand what surprises me is that:
>> issparse (B)
ans = 1
>> matrix_type (B)
ans = Rectangular
>> issparse (A)
ans = 1

`>> mat = [A B' spalloc(rows(A),1,0); B spalloc(rows(B),columns(A),1)
``E'; spalloc(columns(A),1,1) E 0];
`>> matrix_type (mat)
ans = Full
>> issparse (mat)
ans = 1
why is mat marked as full???

Also, what does the code
[R, p, q] = chol(A);
nnz(R)

work for Octave and Matlab?

I tried this in Octave, after 30 min it did not finish yet...
I will only be able to try it on Matlab tomorrow.

If so what is the value of NNZ of the factorization in both cases.
Regards
David

Thanks,
Carlo