What this error means is that you tried to send more data than you tried to receive. Specifically, you sent N bytes and tried to receive M, where M<N. MPI does not allow that.

As for the max size of messages that you can send, there are few limits other than the amount of memory that you can allocate to a single process. Theoretically, you can send as large a message as you can have a buffer in your process (assuming that there's some memory left over for Open MPI's internal state and buffering). Open MPI sends large messages in fragments, so in the common case, we only need to be able to have a bunch of fragments allocated at any time in order to keep the network busy.


On Nov 20, 2006, at 2:19 PM, Miquel Dotcom wrote:

Hello,
I'm using openMPI for a paralelization of a fortran90 code. I came accross an error - when I try to send a matrix 400x450 of real*8 (double) I get following error:

[masada:05620] *** An error occurred in MPI_Recv
[masada:05620] *** on communicator MPI_COMM_WORLD
[masada:05620] *** MPI_ERR_TRUNCATE: message truncated
[masada:05620] *** MPI_ERRORS_ARE_FATAL (goodbye)
forrtl: error (78): process killed (SIGTERM)

I understand that the amount of data that can be send by one MPI_SEND call is somehow limited - what is this limitation? can it be somehow augmented? best regards, Michael

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