Nathan, Is is sufficient? Multiple windows can be created on a communicator. So I think PID + CID is not sufficient.
Possible fixes: - The root process creates a filename with a random number and broadcast it in the communicator. - Use per-communicator counter and use it in the filename. Regards, Takahiro Kawashima, MPI development team, Fujitsu > Hmm, I think you are correct. There may be instances where two different > local processes may use the same CID for different communicators. It > should be sufficient to add the PID of the current process to the > filename to ensure it is unique. > > -Nathan > > On Tue, Feb 02, 2016 at 09:33:29PM +0900, Gilles Gouaillardet wrote: > > Nathan, > > the sm osc component uses communicator CID to name the file that will be > > used to create shared memory segments. > > if I understand and correctly, two different communicators coming from > > the > > same MPI_Comm_split might share the same CID, so CID (alone) cannot be > > used to generate a unique per communicator file name > > Makes sense ? > > Cheers, > > Gilles > > > > ---------- Forwarded message ---------- > > From: Peter Wind <peter.w...@met.no> > > Date: Tuesday, February 2, 2016 > > Subject: [OMPI users] shared memory under fortran, bug? > > To: us...@open-mpi.org > > > > Enclosed is a short (< 100 lines) fortran code example that uses shared > > memory. > > It seems to me it behaves wrongly if openmpi is used. > > Compiled with SGI/mpt , it gives the right result. > > > > To fail, the code must be run on a single node. > > It creates two groups of 2 processes each. Within each group memory is > > shared. > > The error is that the two groups get the same memory allocated, but they > > should not. > > > > Tested with openmpi 1.8.4, 1.8.5, 1.10.2 and gfortran, intel 13.0, intel > > 14.0 > > all fail. > > > > The call: > > call MPI_Win_allocate_shared(win_size, disp_unit, MPI_INFO_NULL, > > comm_group, cp1, win, ierr) > > > > Should allocate memory only within the group. But when the other group > > allocates memory, the pointers from the two groups point to the same > > address in memory. > > > > Could you please confirm that this is the wrong behaviour? > > > > Best regards, > > Peter Wind > > > program shmem_mpi > > > > ! > > ! in this example two groups are created, within each group memory is > > shared. > > ! Still the other group get allocated the same adress space, which it > > shouldn't. > > ! > > ! Run with 4 processes, mpirun -np 4 a.out > > > > > > use mpi > > > > use, intrinsic :: iso_c_binding, only : c_ptr, c_f_pointer > > > > implicit none > > ! include 'mpif.h' > > > > integer, parameter :: nsize = 100 > > integer, pointer :: array(:) > > integer :: num_procs > > integer :: ierr > > integer :: irank, irank_group > > integer :: win > > integer :: comm = MPI_COMM_WORLD > > integer :: disp_unit > > type(c_ptr) :: cp1 > > type(c_ptr) :: cp2 > > integer :: comm_group > > > > integer(MPI_ADDRESS_KIND) :: win_size > > integer(MPI_ADDRESS_KIND) :: segment_size > > > > call MPI_Init(ierr) > > call MPI_Comm_size(comm, num_procs, ierr) > > call MPI_Comm_rank(comm, irank, ierr) > > > > disp_unit = sizeof(1) > > call MPI_COMM_SPLIT(comm, irank*2/num_procs, irank, comm_group, ierr) > > call MPI_Comm_rank(comm_group, irank_group, ierr) > > ! print *, 'irank=', irank, ' group rank=', irank_group > > > > if (irank_group == 0) then > > win_size = nsize*disp_unit > > else > > win_size = 0 > > endif > > > > call MPI_Win_allocate_shared(win_size, disp_unit, MPI_INFO_NULL, > > comm_group, cp1, win, ierr) > > call MPI_Win_fence(0, win, ierr) > > > > call MPI_Win_shared_query(win, 0, segment_size, disp_unit, cp2, ierr) > > > > call MPI_Win_fence(0, win, ierr) > > CALL MPI_BARRIER(comm, ierr)! allocations finished > > ! print *, 'irank=', irank, ' size ', segment_size > > > > call c_f_pointer(cp2, array, [nsize]) > > > > array(1)=0;array(2)=0 > > CALL MPI_BARRIER(comm, ierr)! > > 77 format(4(A,I3)) > > if(irank<num_procs/2)then > > if (irank_group == 0)array(1)=11 > > CALL MPI_BARRIER(comm, ierr) > > print 77, 'Group 0, rank', irank, ': array ', array(1), ' ',array(2) > > CALL MPI_BARRIER(comm, ierr)!Group 1 not yet start writing > > CALL MPI_BARRIER(comm, ierr)!Group 1 finished writing > > print 77, 'Group 0, rank', irank, ': array ', array(1),' ',array(2) > > if(array(1)==11.and.array(2)==0)then > > print *,irank,' correct result' > > else > > print *,irank,' wrong result' > > endif > > else > > CALL MPI_BARRIER(comm, ierr) > > CALL MPI_BARRIER(comm, ierr)!Group 0 finished writing > > print 77, 'Group 1, rank', irank, ': array ', array(1),' ',array(2) > > if (irank_group == 0)array(2)=22 > > CALL MPI_BARRIER(comm, ierr) > > print 77, 'Group 1, rank', irank, ': array ', array(1),' ',array(2) > > if(array(1)==0.and.array(2)==22)then > > print *,irank,' correct result' > > else > > print *,irank,' wrong result' > > endif > > endif > > > > call MPI_Finalize(ierr) > > > > end program
