Thank you for your suggestion, I tried this solution, but it doesn't work. In fact, the headnode doesn't participate the computing and communication, it only malloc a large a memory, and when the loop in every PS3 is over, the headnode gather the data from every PS3.
The strange thing is that sometimes the program can work well, but when reboot the system, without any change to the program, it can't work, so I think it should be some mechanism in OpenMPI that can configure to let the program work well.
 
Lin

From: users-bounces@open-mpi.org [mailto:users-bounces@open-mpi.org] On Behalf Of Doug Reeder
Sent: 2009年7月7日 10:49
To: Open MPI Users
Subject: Re: [OMPI users] Configuration problem or network problem?

Lin,

Try -np 16 and not running on the head node.

Doug Reeder
On Jul 6, 2009, at 7:08 PM, Zou, Lin (GE, Research, Consultant) wrote:

Hi all,
    The system I use is a PS3 cluster, with 16 PS3s and a PowerPC as a headnode, they are connected by a high speed switch.
    There are point-to-point communication functions( MPI_Send and MPI_Recv ), the data size is about 40KB, and a lot of computings which will consume a long time(about 1 sec)in a loop.The co-processor in PS3 can take care of the computation, the main processor take care of point-to-point communication,so the computing and communication can overlap.The communication funtions should return much faster than computing function.
    My question is that after some circles, the time consumed by communication functions in a PS3 will increase heavily, and the whole cluster's sync state will corrupt.When I decrease the computing time, this situation just disappeare.I am very confused about this.
I think there is a mechanism in OpenMPI that cause this case, does everyone get this situation before?
I use "mpirun --mca btl tcp, self -np 17 --hostfile ...", is there something i should added?
Lin
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