[petsc-users] Efficient interaction of local and distributed Mat/Vec

[Thomas Witkowski]

In my FETI-DP code, there are many interactions between local and  
distributed data structures (matrices, vectors). Mainly, there is on  
each rank a matrix mat_bb (MATSEQAIJ) representing the local subdomain  
problem (without the primal nodes). In my implementation, the  
corresponding vector f_b is a distributed VECMPI. Thus, on each rank  
the local part of f_b corresponds to the size of the local matrix  
mat_bb. For each solution with mat_bb and the right-hand-side f_b, my  
code creates a temporary vector f_b_seq (VECSEQ), creates two IS (for  
the global indices in f_b and the local in f_b_seq), and copy the  
values from f_b to f_b_seq with a VecScatter. After the solution with  
m_b_b, the same is done the other way round.

This works fine. My question: Is this the best/most efficient way to  
do it with PETSc? I'm not really sure. It's a lot of code and I do not  
like the idea of coping the same value from one date structure to  
another one just to make them "compatible" in some way.

Thanks for any suggestions,

Thomas