Hi, I am confusing to the allocation for a parallel matrix in PETSC manual,
"If PETSC DECIDE is not used for the arguments m and n, then the user must ensure that they are chosen to be compatible with the vectors. To do this, one first considers the matrix-vector product y = Ax. The m that is used in the matrix creation routine MatCreateMPIAIJ() must match the local size used in the vector creation routine VecCreateMPI() for y. Likewise, the n used must match that used as the local size in VecCreateMPI() for x." Since the process holds all the columns, why does it only hold part of vector x? Is it convenient for the matrix vector multiplication? Thanks. Yixun
