Juan,

it is possible that the problem is not in MPI - I've seen similar problem on some of our workstations some time ago. Juan, are you sure you can allocate more than 2x 4GB memory of data in non-mpi program on your system?

Thanks,
Jelena

On Wed, 1 Aug 2007, George Bosilca wrote:

Juan,

I have to check to see what's wrong there. We build Open MPI with
full support for data transfer up to sizeof(size_t) bytes. so you
case should be covered. However, there are some known problems with
the MPI interface for data larger than sizeof(int). As an example the
_count field in the MPI_Status structure will be truncated ...

  Thanks,
    george.

On Jul 30, 2007, at 1:47 AM, Juan Carlos Guzman wrote:

Hi,

Does anyone know the maximum buffer size I can use in MPI_Send()
(MPI_Recv) function?. I was doing some testing using two nodes on my
cluster to measure the point-to-point MPI message rate depending on
size. The test program exchanges MPI_FLOAT datatypes between two
nodes. I was able to send up to 4 GB of data (500 Mega MPI_FLOATs)
before the process crashed with a segmentation fault message.

Is the maximum size of the message limited by the sizeof(int) * sizeof
(MPI data type) used in the MPI_Send()/MPI_Recv() functions?

My cluster has openmpi 1.2.3 installed. Each node has 2 x dual core
AMD Opteron and 12 GB RAM.

Thanks in advance.
   Juan-Carlos.
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--
Jelena Pjesivac-Grbovic, Pjesa
Graduate Research Assistant
Innovative Computing Laboratory
Computer Science Department, UTK
Claxton Complex 350
(865) 974 - 6722 (865) 974 - 6321
jpjes...@utk.edu

"The only difference between a problem and a solution is that
 people understand the solution."
                                      -- Charles Kettering

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