[mpich-discuss] Buffered send and tcp on Windows

[Mikko Lyly]

>>You are sending 1000 integers = 4000 bytes. The buffer is 10000 bytes, so it
>>has room for only 2 bsends.
>>
>>Rajeev
>
>Thank you for the reply.
>
>But isn't the buffer size in the test case 40000 bytes (10000 integers have been allocated for the send buffer)? It should be plenty enough for 3 times 1000 integers?

I'm sorry, you are of course right.

The correct line to attach the buffer should be

  CALL MPI_BUFFER_ATTACH(send_buf, sizeof(send_buf), rc)

Sorry for the inconvenience.

Mikko






>________________________________________
>From: owner-mpich-discuss at mcs.anl.gov [owner-mpich-discuss at mcs.anl.gov] On Behalf Of Rajeev Thakur [thakur at mcs.anl.gov]
>Sent: Friday, August 29, 2008 9:57 PM
>To: mpich-discuss at mcs.anl.gov
>Subject: RE: [mpich-discuss] Buffered send and tcp on Windows

>You are sending 1000 integers = 4000 bytes. The buffer is 10000 bytes, so it
>has room for only 2 bsends.
>
>Rajeev

Thank you for the reply.

But isn't the buffer size in the test case 40000 bytes (10000 integers have been allocated for the send buffer)? It should be plenty enough for 3 times 1000 integers?

Mikko



> -----Original Message-----
> From: owner-mpich-discuss at mcs.anl.gov
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Mikko Lyly
> Sent: Friday, August 29, 2008 1:45 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: [mpich-discuss] Buffered send and tcp on Windows
>
> Dear all,
>
> I have a small question related to MPICH2 1.0.7, and I was
> hoping if you could help me to understand the case a little
> bit better.
>
> Attached to this mail (see below) is a small sample program
> in f90, which fails to run both on Linux and Windows when
> executed as follows:
>
> $ mpiexec -localonly 4 test
>
> It runs fine for n=1,2,3.  For  n=4 and grater, I get:
>
> Fatal error in MPI_Bsend: Invalid buffer pointer, error stack:
> MPI_Bsend(182).......: MPI_Bsend(buf=0023EE50, count=1000,
> MPI_INTEGER, dest=3, tag=1000, MPI_COMM_WORLD) failed
> MPIR_Bsend_isend(342): Insufficient space in Bsend buffer;
> requested 4000; total buffer size is 10000
>
> I fail to understand, why is the buffer size not sufficient
> (sending 3000, bufsize is 10000), and why the error is
> "requested 4000"?
>
> Thank you and have a very nice weekend,
> Mikko Lyly
>
>
> PROGRAM test
>   IMPLICIT NONE
>   INCLUDE 'mpif.h'
>   INTEGER :: receiver, sender, rc, ntasks, id
>   INTEGER :: status(MPI_STATUS_SIZE)
>   INTEGER, PARAMETER :: send_buf_size = 10000
>   INTEGER, PARAMETER :: data_buf_size = 1000
>   INTEGER :: send_buf(send_buf_size)
>   INTEGER :: data_buf(data_buf_size)
>
>   CALL MPI_INIT(rc)
>   CALL MPI_COMM_SIZE(MPI_COMM_WORLD, ntasks, rc)
>
>   CALL MPI_COMM_RANK(MPI_COMM_WORLD, id, rc)
>   CALL MPI_BUFFER_ATTACH(send_buf, send_buf_size, rc)
>
>   ! Sending (ntasks-1) times 1000 integers (buffer size is 10000):
>   DO receiver = 0, ntasks-1
>      IF(receiver /= id) THEN
>         PRINT *, 'Send:', id, '->', receiver
>         CALL MPI_BSEND(data_buf, data_buf_size, MPI_INTEGER,
> receiver, 1000, MPI_COMM_WORLD, rc)
>      END IF
>   END DO
>
>   ! Receiving (ntasks-1) times 1000 integers:
>   DO sender = 0, ntasks-1
>      IF(sender /= id) THEN
>         PRINT *, 'Recv:', sender, '->', id
>         CALL MPI_RECV(data_buf, data_buf_size, MPI_INTEGER,
> sender, 1000, MPI_COMM_WORLD, status, rc)
>      END IF
>   END DO
>
>   CALL MPI_FINALIZE(rc)
>
> END PROGRAM test
>
>