Dear Nasos, thank you for the quick answer.

I will consider using the find functions.

concerning the construction of the matrix we are actually using our own version of vector of vectors. If you are interested you can have a look to our implementation at the link

http://kratos.cimne.upc.es/trac/browser/kratos/kratos/solving_strategies/builder_and_solvers/residualbased_elimination_builder_and_solver.h

from line 965

what you may find of interest is the first touch approach we use for the matrix in openmp context. This has a very important effect on performance on numa machines, starting from line 1034 in the same file

in any case thanks a lot for your attention

Riccardo

On Thu, 12 Aug 2010 10:01:35 -0400, Nasos Iliopoulos <nasos_i@hotmail.com> wrote:

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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