Non Blocking communication in MPI and MPI Wait Issue. Not all information is passed correctly?

Either rank 0 or 1 could still be sending data after this block of code has been executed (as you don't wait on the send request object). This could cause problems if you modify the data before it has finished sending.

For every call to a non-blocking MPI call, there has to be a corresponding wait. You are missing one wait per process.

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