[scilab-Users] Sparse preprocessing

[Stephane Mottelet]

Pedro Ledoux <p_ledoux at yahoo.com.br> a écrit :

> The method of finite diferences frequently give us systens of sparse  
> matrix. Are you using this one? I had some recent experience with  
> it. When the sparse matrix has a 3 diagonal behavior the most  
> eficient thing I tested was thomas method. But We can't use it when  
> the non 0 elements has no pattern :/
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>  I've used the finite difference method to solve a problem of the  
> propagation of a wave in a wave guide. In this the sparse system to  
> a "L" shaped wave guide gave me a sparse matrix with no pattern to  
> non 0 elements. In the case of waveguide it lead me to a eigenvalue  
> problem. Unfortunately I didn't found a function like eig() from  
> Matlab, is there something similat in Scilab?

the functions you might be interested in are "spec" and "bdiag"

S.

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>
> --- Em sáb, 2/10/10, Wojciech Artichowicz <w_artichowicz at o2.pl> escreveu:
>
> De: Wojciech Artichowicz <w_artichowicz at o2.pl>
> Assunto: [scilab-Users] Sparse preprocessing
> Para: users at lists.scilab.org
> Data: Sábado, 2 de Outubro de 2010, 7:30
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> Hello,
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> Fluid mechanics computations often lead to sparse
> matrix systems.  Scilab has marvellous sparse functions, however
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> I cannot find any function for sparse preprocessing. For
> example:
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> I have built quite big system with sparse matrix with
> no explicit pattern of non-zero elements. The best way to solve this  
> system is
> to use
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> modified SOR method (my own implementation). My
> question is:
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> Is there any function in Scilab that would remove
> zero entries from diagonal (which isn?t in this case very easy), and that
> would do some additional stuff like
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> placing at diagonal the biggest possible element.
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> If no, is there any well known not too complicated
> algorithm for such a purpose?
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> Thank You in advance,
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> Regards,
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> W.A.
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