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Subject: Re: [OMPI users] OpenMPI how large its buffer size ?
From: jody (jody.xha_at_[hidden])
Date: 2010-07-12 06:31:08


Hi
> mpi_irecv(workerNodeID, messageTag, bufferVector[row][column])
OpenMPI contains no function of this form.
There is MPI_Irecv, but it takes a different number of arguments.

Or is this a boost method?
If yes, i guess you have to make sure that the
bufferVector[row][column] is large enough...
Perhaps there is a boost forum you can check out if the problem persists

Jody

On Sun, Jul 11, 2010 at 10:13 AM, Jack Bryan <dtustudy68_at_[hidden]> wrote:
> thanks for your reply.
> The message size is 72 bytes.
> The master sends out the message package to each 51 nodes.
> Then, after doing their local work, the worker node send back the same-size
> message to the master.
> Master use vector.push_back(new messageType) to receive each message from
> workers.
> Master use the
> mpi_irecv(workerNodeID, messageTag, bufferVector[row][column])
> to receive the worker message.
> the row is the rankID of each worker, the column is index for  message from
> worker.
> Each worker may send multiple messages to master.
> when the worker node size is large, i got MPI_ERR_TRUNCATE error.
> Any help is appreciated.
> JACK
> July 10  2010
>
> ________________________________
> Date: Sat, 10 Jul 2010 23:12:49 -0700
> From: eugene.loh_at_[hidden]
> To: users_at_[hidden]
> Subject: Re: [OMPI users] OpenMPI how large its buffer size ?
>
> Jack Bryan wrote:
>
> The master node can receive message ( the same size)  from 50 worker nodes.
> But, it cannot receive message from 51 nodes. It caused "truncate error".
>
> How big was the buffer that the program specified in the receive call?  How
> big was the message that was sent?
>
> MPI_ERR_TRUNCATE means that you posted a receive with an application buffer
> that turned out to be too small to hold the message that was received.  It's
> a user application error that has nothing to do with MPI's internal
> buffers.  MPI's internal buffers don't need to be big enough to hold that
> message.  MPI could require the sender and receiver to coordinate so that
> only part of the message is moved at a time.
>
> I used the same buffer to get the message in 50 node case.
> About ""rendezvous" protocol", what is the meaning of "the sender sends a
> short portion "?
> What is the "short portion", is it a small mart of the message of the sender
> ?
>
> It's at least the message header (communicator, tag, etc.) so that the
> receiver can figure out if this is the expected message or not.  In
> practice, there is probably also some data in there as well.  The amount of
> that portion depends on the MPI implementation and, in practice, the
> interconnect the message traveled over, MPI-implementation-dependent
> environment variables set by the user, etc.  E.g., with OMPI over shared
> memory by default it's about 4Kbytes (if I remember correctly).
>
> This "rendezvous" protocol" can work automatically in background without
> programmer
> indicates in his program ?
>
> Right.  MPI actually allows you to force such synchronization with
> MPI_Ssend, but typically MPI implementations use it automatically for
> "plain" long sends as well even if the user didn't not use MPI_Ssend.
>
> The "acknowledgement " can be generated by the receiver only when the
> corresponding mpi_irecv is posted by the receiver ?
>
> Right.
>
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