Lisandro Dalcin <[email protected]> writes: >> I'm not sure of this suggested change, in that a >> "bad for MPI-IO" workload (like each rank randomly seeking around a big >> file) might not be better with rank 0 acting as a service rank. >> > > Please note my main question is unrelated to MPI-IO. It is about the > original POSIX-based implementation of binary viewers. For mode READ, all > processes open the file (with the open() system call), but in the current > implementation, only process zero ever reads the file (unless the user gets > the file descriptor and start issuing low-level PetscBinaryRead() calls). > So I do not see the point of opening the file on all processes (and then > stress metadata servers on parallel filesystem), if we are not going to > ever read from rank != 0. Let's just fix things to open the file at rank==0 > only.
Okay, this much I agree on. If a rank doesn't actually read, it shouldn't open the file to read.
