Re: [ublas] simple question on CSR matrix

Subject: Re: [ublas] simple question on CSR matrix
From: rrossi_at_[hidden]
Date: 2010-08-12 11:05:20

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  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_at_[hidden]
> To:
ublas_at_[hidden]
> 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
> 
> -- 
>
________________________________________________________________
> Riccardo
Rossi, Ph.D, Civil Engineer
> member of the Kratos Group:
kratos.cimne.upc.es
> Centro Internacional de Métodos Numéricos en
Ingeniería (CIMNE)
> Universidad Politécnica de Cataluña (UPC)
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C-1, campus Norte UPC
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> Tel.
([phone]
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