Re: [mpich-discuss] Failed to allocate memory for an unexpected message

16 Jan 2014

      Hi Pavan and Antonio,

I implemented the scheme you suggested and it was much easier than I
thought. Very nice, thanks for your help.

However, I noticed that the execution times were much higher than the cases
in which the failure didn't occur.
Is there any reason, apart from some implementation mistake, to explain
this behavior?

I don't know if it would help, but I am sending below part of the receiver
process Fortran code.

Thanks in advance.

Best regards,
Luiz

c-----------------------------------------------------------------------
      subroutine my_receiver
c     ------------------------------------------------------------------
      (...)

c     Local
c     -----
      integer*4 m_stat(MPI_STATUS_SIZE)

      integer*4 m_request(zrecv)        ! request identifier
for asynchronous receives
      character card(zrecv)*(zbuf)      ! buffer for receiving messages

c     Pre-post RECVs
c     --------------
      do irecv = 1, zrecv
        call MPI_IRECV(card(irecv), zbuf, MPI_CHARACTER,
     .                 MPI_ANY_SOURCE, MPI_ANY_TAG, M_COMM_SDDP,
     .                 m_request(irecv), m_ierr )
      end do !irecv

      do while( keep_receiving )

c       Wait for any of the pre-posted requests to arrive
c       -------------------------------------------------
        call MPI_WAITANY(zrecv, m_request, irecv, m_stat, m_ierr)

c       Process message: disk IO
c       ---------------
        <DO SOMETHING>
        if( SOMETHING_ELSE ) then
          keep_receiving = .false.
        end if

c       Re-post RECV
c       ------------
        call MPI_IRECV(card(irecv), zbuf, MPI_CHARACTER,
     .                 MPI_ANY_SOURCE, MPI_ANY_TAG, M_COMM_SDDP,
     .                 m_request(irecv), m_ierr)

      end do

c     Cancel unused RECVs
c     -------------------
      do irecv = 1, zrecv
        call MPI_CANCEL( m_request(irecv), m_ierr )
      end do !irecv

      (...)

      return
      end

On 1 November 2013 22:14, Luiz Carlos da Costa Junior <[email protected]>wrote:
...
Thanks
On 1 November 2013 22:00, Pavan Balaji <[email protected]> wrote:
...
On Nov 1, 2013, at 4:30 PM, Luiz Carlos da Costa Junior <[email protected]>
wrote:
...
I understand that I will have to have N buffers, one for each posted
MPI_Irecv. I will also have to TEST (using MPI_PROBE or MPI_WAITANY) until
a message comes. The result of this test will identify which one of the
posted MPI_Irecv has actually received the message and then process the
right buffer. Is this correct?
Correct.
...
Should I have to change anything at the sender's processes?
Likely not.  But you need to think through your algorithm to confirm that.
...
At the end, my receiver process receives a message identifying that it
should exit this routine. What should I do with the already posted
MPI_Irecv's? Can I cancel them?
Yes, you can with MPI_CANCEL.
—- Pavan
--
Pavan Balaji
http://www.mcs.anl.gov/~balaji
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Luiz Carlos da Costa Junior

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