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Subject: [OMPI users] Myid changes to 0 after using a mpi_recv
From: Anton Morgan (amorgan.cartech_at_[hidden])
Date: 2012-04-05 15:39:44


My setup is kinda convoluted unfortunately so this also might be an issue,
but just keep that in the back of your mind for now and assume that is not
the problem. I am using Windows 7 64-bit, with cygwin and compiling using
x86_64-w64-mingw32-gfortran and installed open MPI via
OpenMPI_v1.5.5-1_win64.exe. I have compiled and ran some mpi test programs
I made, but first time using the mpi_send and mpi_recv commands I ran into
this error, or what seems to be an error to me.

Back story: I am trying to run Parallel Pikaia, which is an open source
Genetics Algorithm in Fortran that uses MPI. It should run out of the box
fine, but it does run all processes properly. So I started to troubleshoot
and found that after the first mpi_recv command on the slaves, the myid
changes to 0, but right before the command it is the appropriate myid/rank.
So I made a simple fortran code to test if it was Pikaia or MPI and it
shows to be MPI.

Fortran Code:
c ----------------------------------------------

      program mpi_hello

      implicit none

      include 'mpif.h'

      integer ierr,myid,nproc,rc,flag,nrank,rank
      integer status(MPI_STATUS_SIZE), flag2

c ----------------------------------------------
c Initialize MPI
c ----------------------------------------------
      call mpi_init( ierr )
      call mpi_comm_rank( MPI_COMM_WORLD, myid, ierr )
      call mpi_comm_size( MPI_COMM_WORLD, nproc, ierr )
      nrank=nproc-1

c ----------------------------------------------
c Master portion
c ----------------------------------------------
      if (myid.eq.0) then
         flag=1
         flag2=2
c send two integers to all slaves
         do rank=1,nrank
         call mpi_send( flag, 1, MPI_INTEGER, rank,
     + 1, MPI_COMM_WORLD, ierr )
         print 8, flag, myid
   8 format('Master says, Flag: ',i0.1, ' MyID: ', i0.1)
         call mpi_send( flag2, 1, MPI_INTEGER, rank,
     + 1, MPI_COMM_WORLD, ierr )
         print 10, flag2, myid
   10 format('Master says, Flag2: ',i0.1, ' MyID: ', i0.1)
         enddo
c ----------------------------------------------
c Slave portion
c ----------------------------------------------
      elseif (myid.ne.0) then
c to see ID before mpi_rcv
         print *, 'Slave: ', myid
         call mpi_recv( flag, 1, MPI_INTEGER, 0,
     + 1, MPI_COMM_WORLD, status, ierr )
c check myid after recv which turns to 0 on my environment
         print 9, flag, myid
   9 format('Slave says, Flag: ',i0.1, ' MyID: ', i0.1)
         call mpi_recv( flag2, 1, MPI_INTEGER, 0,
     + 1, MPI_COMM_WORLD, status, ierr )
         print 11, flag2, myid
   11 format('Slave says, Flag2: ',i0.1, ' MyID: ', i0.1)
      endif

      call mpi_finalize(rc)
      stop
      end
c ----------------------------------------------

Simple makefile for my environment:
#
# MPI makefile
#
#INSTALL_DIR = ./
F77 = x86_64-w64-mingw32-gfortran
# Progra~2 because it is located in Program Files (x86)
LIB = -L/cygdrive/c/Progra~2/OpenMPI_v1.5.5-x64/bin
INCLUDE = -I/cygdrive/c/Progra~2/OpenMPI_v1.5.5-x64/include
FFLAGS =
MAKE = make
SHELL = /bin/sh
#
### End User configurable options ###

SRC1 = mpihello
OBJS = $(SRC1).o

pikaia : $(OBJS)
    $(F77) $(FFLAGS) -o mpihello $(OBJS) $(LIB) -lmpi_f77
# rm -f *.o

$(SRC1).o : $(SRC1).f
    $(F77) $(FFLAGS) $(INCLUDE) -c $(SRC1).f

So I am wondering if this is something that is an issue with the current
build of openMPI , if I am missing something or if it's my convoluted
environment. Attached is the source and makefile of what is above and then
my built .exe and a libgcc_s_sjlj-1.dll to run the .exe.

Thank you for the help

-- 
*AMorgan*