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Re: [Getfem-users] submatrix addressing and assignment of this to a csr

From: Andriy Andreykiv
Subject: Re: [Getfem-users] submatrix addressing and assignment of this to a csr matrix
Date: Wed, 4 May 2011 11:42:05 +0200

Hi Umut,

Regarding the assignment, probably the easiest way is:
if A and B are your matrices and you want to place a part of A into a
part of B (or the whole A into part of B, or any combinations)

gmm::copy(  gmm::sub_matrix(A, gmm::sub_interval(startAX, sizeAX),
gmm::sub_interval(startAY, sizeAY)),
                   gmm::sub_matrix(B, gmm::sub_interval(startBX,
sizeBX), gmm::sub_interval(startBY, sizeBY))   )
of course the sizes should match: sizeAXY=sizeBXY etc. .

besides the intervals you can use sorted and unsorted indices

regarding the iterating on the components of a matrix read:

Best regards,

2011/5/3 Umut Tabak <address@hidden>:
> Dear all,
> I was using ublas for some matrix interfacing operations however they lack
> an efficient addressing scheme for a submatrix. Since gmm++ is designed to
> be used in a FE framework, I thought that it could give me what  I like.
> Here is my goal: I would like assign to some sparse matrices which I have
> the structure, the nnz info for rows or so, I also read the documentation
> and sub_index seems to be the answer and later on sub_matrix returns a
> reference to a matrix.
> So the questions are
> + what would be the most efficient way to assign this matrix(or the
> reference) to a csr or csc matrix?
> + what would be the most efficient way to iterate over the nnz of this newly
> generated matrix?
> Best wishes,
> Umut
> _______________________________________________
> Getfem-users mailing list
> address@hidden

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