[OMPI users] MPI_Isend delay

[dave fournier]

I have a master-slave setup. I have noticed that when I send a message 
from the master to the slave
processes using MPI_Isend it never gets sent until I encounter an 
MPI_recv  in the master process.
As a result rhe slave processes are wasting time waiting for the 
message.  If I use MPI_Send
instead of MPI_Isend all works fine.  I don't understand what is going 
on here.