Sorry, I seem to have misread your post. You're not actually invoking
MPI_Alltoall or MPI_Alltoallv. Please disregard my last post.....
Simon.
On 26/04/2013 23:14, Stephan Wolf wrote:
Hi,
I have encountered really bad performance when all the nodes send data
to all the other nodes. I use Isend and Irecv with multiple
outstanding sends per node. I debugged the behavior and came to the
following conclusion: It seems that one sender locks out all other
senders for one receiver. This sender releases the receiver only when
there are no more sends posted or a node with lower rank, wants to
send to this node (deadlock prevention). As a consequence, node 0
sends all its data to all nodes, while all others are waiting, then
node 1 sends all the data, …
What is the rationale behind this behaviour and can I change it by
some MCA parameter?
Thanks
Stephan
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