Hello everyone, I am a novice to Petsc and parallel computing. I have created a mpi sparse matrix A (size n-by-n) and a parallel vector b (size n-by-1). Now I want to modify the diagonal of A by adding the values of vector b. Namely, A(i,i) = A(i,i) + b(i) and all the off-diagonal elements remains the same. I am worrying that when I use MatSetValue or MatSetValues, b(i) may not be accessed by some particular processor since VecGetValues can only get values on the same processor. One possible solution I am thinking is converting vector b to a diagonal matrix B and then do the MatAXPY operation. However, using MatSetValue to set diagonal elements of B, B(i,i) = b(i), still faces the similar problem. Can anyone give me some suggestion? Thanks.
Best, Xiangdong P.S. When I compiled my program, I get warnings like that: warning: return makes pointer from integer without a cast. Actually, these lines are standard Petsc functions like that: ierr = VecCreate(PETSC_COMM_WORLD,&x);CHKERRQ(ierr); ierr = VecDestroy(x); CHKERRQ(ierr); How can I get rid of these warnings? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110427/b1c63a14/attachment.htm>
