Gilles, I see. Thanks!
Takahiro Kawashima, MPI development team, Fujitsu > Kawashima-san, > > we always duplicate the communicator, and use the CID of the duplicated > communicator, so bottom line, > there cannot be more than one window per communicator. > > i will double check about using PID. if a broadcast is needed, i would > rather use the process name of rank 0 in order to avoid a broadcast. > > Cheers, > > Gilles > > On 2/3/2016 8:40 AM, Kawashima, Takahiro wrote: > > 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
