Re: large sparse matrix

[David Bateman]

Carlo de Falco wrote:
> 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
What are the sizes of A, B and E?

D.


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