Hi everyone, I have a question about how MPI works. Currently I have a job running on MPI on the mode master_slave, I mean that every slave executes a separate task without communicate with the others slaves, once a slave-node finishes, it sends a warning to the master and then the master delivers another job to the free slave. Now, the master is in a do-loop with a parameter say k and I wish to deliver jobs from k_init to k_end; but here is the catch. By some strange reason, at the middle of the do-loop on k, one slave finishes running the task, but never it never warns the master that it finishes, I mean: Call ProgramaCentral(kRank) ! Some slave node executes succesfully the task Call MPI_Send( masterBuf, 3, MPI_INTEGER, 0, 0, MPI_COMM_WORLD, ierrMPI ) ! Some slave never warns the master It appears that it get stuck in the limbo between these two lines.