[petsc-users] How to obtain the local matrix from a global matrix in DMDA?

[Jed Brown]

Could you explain more of what you mean by "local matrix"? If you're thinking of finite elements, then that doesn't exist and can't readily be constructed except at assembly time (see MATIS, for example). If you mean an overlapping block, then MatGetSubMatrix() or MatGetSubMatrices(), as used inside PCASM. If you mean only the diagonal block, then see MatGetDiagonalBlock(). 

liluo <liluo at um.edu.mo> writes:

> Dear developers,
>
>
> I created a DMDA object and obtain the local vector from a global vector by using DMGlobalToLocalBegin/End.
>
> How can I obtain the corresponding local matrix from the global matrix?
>
> In my case, the global matrix is of MPIBAIJ type created by DMCreateMatrix(da,MATBAIJ,&A);
>
>
> Bests,
>
> LI