Question

我有程序，我正在使用MPI进行并行化。我附加了测试代码，它将数组分解为沿着给定数量的处理器的多个分段，然后我使用广播来组合来自所有进程的结果并将其分配给所有进程。当所有处理器的分发不相同并导致广播失败时，会出现此问题。我附上了以下代码，它适用于6个进程，但不适用于8个进程。

  program main

  include 'mpif.h'

  integer i, rank, nprocs, count, start, stop, nloops
  integer err, n1
  REAL srt, sp
  REAL b(1,1:10242)
  REAL c(1,1:10242)
  integer, Allocatable :: jjsta(:), jjlen(:)
  allocate (jjsta(0:nprocs-1),jjlen(0:nprocs-1))
  call MPI_Init(ierr)


  call MPI_Comm_rank(MPI_COMM_WORLD, rank, ierr)
  call MPI_Comm_size(MPI_COMM_WORLD, nprocs, ierr)

  n1 = 10242
  call para_range(1,n1,nprocs,rank,start,stop)
  jjsta(rank) = start
  jjlen(rank) = stop -start +1
  srt = MPI_WTIME()
  do i=start,stop
    c(1,i) = i
  enddo
  sp =MPI_WTIME()
  print *,"Process ",rank," performed ", jjlen(rank), &
         " iterations of the loop."
  !      CALL MPI_ALLGATHERV(c(1,jjsta(rank)), jjlen(rank), MPI_REAL,&
  !          b,jjlen(rank),jjsta(rank)+jjlen(rank)+1,MPI_REAL,MPI_COMM_WORLD,ierr)
  CALL MPI_BCAST(c(1,jjsta(rank)), jjlen(rank), MPI_REAL,&
       rank, MPI_COMM_WORLD, ierr)

  call MPI_Finalize(ierr)
  deallocate(jjsta,jjlen)
  end program main


subroutine para_range(n1, n2, nprocs, irank, ista, iend)
integer(4) :: n1 ! Lowest value of iteration variable
integer(4) :: n2 ! Highest value of iteration variable
integer(4) :: nprocs ! # cores
integer(4) :: irank ! Iproc (rank)
integer(4) :: ista ! Start of iterations for rank iproc
integer(4) :: iend ! End of iterations for rank iproc
iwork1 = ( n2 -n1 + 1 ) / nprocs
!    print *, iwork1
iwork2 = MOD(n2 -n1 + 1, nprocs)
!    print *, iwork2
ista = irank* iwork1 + n1 + MIN(irank, iwork2)
iend = ista + iwork1 -1
if (iwork2 > irank) iend = iend + 1
return
end subroutine para_range

当我使用8个处理器运行它时，MPI_Bcast已经注释掉了，这就是它打印出来并且它可以正常工作

 Process             2  performed          1280  iterations of the loop.
 Process             1  performed          1281  iterations of the loop.
 Process             4  performed          1280  iterations of the loop.
 Process             5  performed          1280  iterations of the loop.
 Process             3  performed          1280  iterations of the loop.
 Process             6  performed          1280  iterations of the loop.
 Process             0  performed          1281  iterations of the loop.
 Process             7  performed          1280  iterations of the loop.

但是当我尝试将所有结果和广播结合起来时，这就是我得到的错误

Fatal error in MPI_Bcast:
Message truncated, error stack:
MPI_Bcast(1128)...................: MPI_Bcast(buf=0x2af182d8d028, count=1280, MPI_REAL, root=4, MPI_COMM_WORLD) failed
knomial_2level_Bcast(1268)........:
MPIDI_CH3U_Receive_data_found(259): Message from rank 0 and tag 2 truncated; 5124 bytes received but buffer size is 5120
Process             4  performed          1280  iterations of the loop.

我还尝试了MPI_Allgatherv将结果合并到数组b中，我得到以下错误：

Fatal error in MPI_Allgatherv:
Message truncated, error stack:
MPI_Allgatherv(1050)................: MPI_Allgatherv(sbuf=0x635df8, scount=1280, MPI_REAL,     rbuf=0x62bde8, rcounts=0x2b3ff297b244, displs=0x7fff3ebc1fb0, MPI_REAL, MPI_COMM_WORLD) failed
MPIR_Allgatherv(243)................:
MPIC_Sendrecv(117)..................:
MPIDI_CH3U_Request_unpack_uebuf(631): Message truncated; 5124 bytes received but buffer size is  5120

将数组合并到我时的问题似乎是它没有更新正在发送的数组的长度。我似乎无法弄清楚如何解决问题，任何帮助将不胜感激。谢谢。

MPI Fortran同步数据

0 个答案: