title: MPI_Scatter: Why do I have to allocate memory in all the processes?
body: <p>I am dealing with parallelizing Conways' Game of Life using MPI (in c++). I have to read a  (very large) matrix from input, then scatter it in slices row-wise, and then process every slice in parallel. The idea I am following is to let only one process deal with the I/O stuff. In particular, process 0 read from file and saves the initial datas into a say RxC matrix, to be scattered among the process in (R/P)xC "slice matrices".
  Now, when I perform the routine MPI_Scatter, the compiler complaints because the "big matrix" is allocated only in the first process. To make things work I have to allocate the big matrix in all the process, even if those remains blank. Is this ordinary, or I am doing something wrong? Is there a way to avoid allocating a blank, useless matrix for every process?
  Thank you guys!</p>