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

[Umut Tabak]

On 05/04/2011 11:42 AM, Andriy Andreykiv wrote:
> 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)
> do:
>
> 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. .
>    
Hi Andriy,

I could not really understand the internals of the library but there is 
a general rule-of-thumb, I suppose. If you are doing a write related 
operation than that should be done with copy and if you would like to do 
some kind of matrix-vector multiplication then you should use csr or csc 
formats where you should copy your gmm::row_matrix< 
gmm::wsvector<double> > K for instance into a csr matrix. Am I right on 
this?

As an experienced user, could you please comment on this?

Thanks for the above tip, by the way.

Umut