On Mon, Jun 17, 2019 at 8:45 AM Eda Oktay via petsc-users < [email protected]> wrote:
> Hello everyone, > > I am trying to find the off diagonal blocks of a matrix. For example, I > partitioned a 10*10 matrix into 4*4 and 6*6 block sub matrices. I need to > find the other blocks in order to find the number of nonzero elements in > them. > > I tried to use MatGetLocalSubMatrix but I couldn't figure out how to give > iscol and isrow. > isrow would be the rows of your local part of the (CSR) matrix (start:end-1), iscol would be two parts, left (0:start) and right (end:N-1) > Also, from the manual, ı understood that MatSetLocalToGlobalMapping should > be used before this routine > I don't understand what you are referring to, but I am confused about what you are trying to do. Perhaps you can explain what you are trying to accomplish and we can help you with the details. Thanks, Mark > but I couldn't used it properly because before MatGetLocalSuMatrix, the > submatrix doesn't exist. I tried to give zero to all elements so that I can > use Mapping routine, but I got an error saying that it is invalid. > > How can I fix this probelm? > > Thank you, > > Eda >
