Hi all,
I would like to learn more about communcation mode and wonder if
there are any codes for demonstrating the differences between each mode.
Thinking about the following case, a all-to-all communication performed
in a loop
for (t=0; t<NC; t++) // NC computers in the parallel network
{
if (t!=myrank) // don't send the message to myself
{
if (t<myrank) // avoid deadlock
{
// N stands for the size of buffer to be sent or received, N>100
MPI_Send(send_buf, N, MPI_INT, to, stag, MPI_COMM_WORLD);
MPI_Recv(recv_buf, N, MPI_INT, from, rtag, MPI_COMM_WORLD,
MPI_STATUS_IGNORE);
}
else
{
MPI_Recv(recv_buf, N, MPI_INT, from, rtag, MPI_COMM_WORLD,
MPI_STATUS_IGNORE);
MPI_Send(send_buf, N, MPI_INT, to, stag, MPI_COMM_WORLD);
}
}
}
In the above code, blocking send/receive in stand mode have been used.
I have few questions about the send/recive process.
1) Because the send/recive procedure are run in a loop, for blocking
methods, will the loop pause until the current send/receive procedure
are finished?
2) If nonblocking send/recv are imposed, will the loop go on without
waiting the send/recv's finish? If so, how can I make sure the
each node receive the correct data (i.e. each send-receive procedure go
without any problem)?
3) Will the answer of 1) 2) change in other communcation mode?
Thanks in advance.
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