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Subject: [OMPI users] AlltoallV (with some zero send count values)
From: Timothy Stitt (Timothy.Stitt.9_at_[hidden])
Date: 2012-03-06 16:43:11


Hi all,

Can anyone tell me whether it is legal to pass zero values for some of the send count elements in an MPI_AlltoallV() call? I want to perform an all-to-all operation but for performance reasons do not want to send data to various ranks who don't need to receive any useful values. If it is legal, can I assume the implementation is smart enough to not send messages when the send count is 0?

FYI: my tests show that AlltoallV operations with various send count values set to 0...hangs.

Thanks,

Tim.