[mpich-discuss] MPI_PUT Implementation Bug or Pilot Error?

[Timothy Stitt]

Hi all,

I've come across some strange behavior with a code that uses MPI_PUT(). I can confirm that this problem appears in older MPICH2 v1.4.x releases as well as the latest MPICH v3.0.3 release. I can also confirm that I receive the correct results when using Open MPI.

I am attaching a reproducer code below that simulates the problem I am having (following the code will hopefully explain its purpose better than what I can describe here in a few lines). This case is hardcoded for a 4-process run. For some reason MPICH implementations are losing some data elements and duplicating others after the communication is complete. I would be grateful if someone can confirm whether this is indeed an implementation bug or a subtle problem with how I've implemented the one-sided communication.

Thanks in advance,

Tim.

program reproducer

  use mpi

  implicit none

  integer :: error,dum_com(2),my_rank,i
  integer :: win_values_points, type_integer,NProc=4
  INTEGER(KIND=MPI_ADDRESS_KIND) :: win_values_size, target_disp
  integer,allocatable :: neighbor_values(:), ncount_in(:)

  call MPI_INIT(error)
  call MPI_COMM_RANK(MPI_COMM_WORLD,my_rank,error)

  CALL MPI_Type_size(MPI_INTEGER,type_integer,error)

  ! Calculate Size Of Window (in bytes)
  win_values_size=2*type_integer*NProc

  ! Allocate Window Storage
  allocate(neighbor_values(0:2*Nproc-1))
  neighbor_values=0

  ! Define Input Values
  allocate(ncount_in(NProc))
  if (my_rank .eq. 0) ncount_in = (/1,2,3,4/)
  if (my_rank .eq. 1) ncount_in = (/5,6,7,8/)
  if (my_rank .eq. 2) ncount_in = (/9,10,11,12/)
  if (my_rank .eq. 3) ncount_in = (/13,14,15,16/)

  ! Create Window
  CALL MPI_WIN_CREATE(neighbor_values, win_values_size, type_integer, MPI_INFO_NULL, MPI_COMM_WORLD, win_values_points, error)   ! Create Neighbor Storage Win
dow
  call MPI_Win_Fence(0,win_values_points,error)

  ! Print pre-communication data
  print*,my_rank,ncount_in
  call flush(5)
  call MPI_BARRIER(MPI_COMM_WORLD,error)

  ! Communicate Data Values to all proceses
  do i = 1,4
     target_disp=2*my_rank
     dum_com(1)=ncount_in(i)
     dum_com(2)=99
     CALL MPI_PUT(dum_com,2,MPI_INTEGER,Nproc-i,target_disp,2,MPI_INTEGER,win_values_points,error)
  end do

  call MPI_Win_Fence(0,win_values_points,error)

  ! Print post-communication values
  print *
  print *,my_rank,neighbor_values
  call flush(5)
  call MPI_BARRIER(MPI_COMM_WORLD,error)

  ! Free Window Storage
  call mpi_win_free(win_values_points,error)

  call MPI_FINALIZE(error)

end program reproducer