Ricardo,

you can use the find_element(i,j) member function, that returns a pointer to the element when it exists and 0 otherwise.

Also for filling sparse matrices, I would suggest taking a look at Gunter's wiki:

http://ublas.sourceforge.net/refdoc/classboost_1_1numeric_1_1ublas_1_1compressed__matrix.html

and playing a bit with the various sparse matrix types.

I find that for FEA, it is usually more efficient to use a generalized_vector_of_vector to assemble the matrix and then copy that into a compressed_matrix, to send it to a solver. Of course this process heavily depends on problem size.

Best,
Nasos


> From: rrossi@cimne.upc.edu
> To: ublas@lists.boost.org
> Date: Thu, 12 Aug 2010 14:21:58 +0200
> Subject: [ublas] simple question on CSR matrix
>
> Dear list,
>
> i have a CSR matrix, of which i preallocated the zeros doing
> push_back
>
> is there a way to ensure that if i access
> A(i,j) and i,j is not in the graph an error is thrown? i mean... i would
> prefer an error (even segfault) than ublas silently attempting to resize
> the matrix
>
> any hint is very welcome
>
> thank you
> Riccardo
>
> --
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