我想将处理器1的派生类型xyzBuffer复制到处理器0的xyz。我尝试使用MPI_GATHER：
call MPI_GATHERV(xyzBuffer,1,inewtype,xyz,1, dispGather,inewtype,0,icomm,ierr)
但处理器0的内存位不会被写入：似乎MPI_GATHER不允许收集派生类型。我使用了MPI_ISEND / MPI_IRECV，但程序挂起在以下代码行：
if ( iproc == 1 ) then
call MPI_ISEND(xyz,1,inewtype,1,itag,icomm,ireq,ierr)
call MPI_WAIT(ireq,istatus,ierr)
else if ( iproc == 0 ) then
call MPI_IRECV(xyz,1,inewtype,0,itag,icomm,ireq,ierr)
call MPI_WAIT(ireq,istatus,ierr)
end if
这些方法是否不适用于派生类型？
以下是完整的程序。我在测试MPI_ISEND，MPI_IRECV块时注释掉了MPI_GATHER，反之亦然。
program type_derived_gather
use nodeinfo
implicit none
include 'mpif.h'
integer(4) :: ierr
integer(4) :: istatus(MPI_STATUS_SIZE)
integer(4) :: i
integer(4) :: j
integer(4) :: iblock(8)
integer(4) :: idisp(8)
integer(4) :: itype(8)
integer(4) :: inewtype
integer(4) :: iextent
integer(4) :: itag
integer(4) :: ireq, isend, irecv
integer(4) :: dispGather ! for root
TYPE :: newXYZ
integer :: x, u
integer :: y, v
integer :: z, w
integer,dimension(3) :: uvw
END TYPE
TYPE (newXYZ) :: xyzBuffer
TYPE (newXYZ) :: xyz
call MPI_INIT(ierr)
icomm = MPI_COMM_WORLD
call MPI_COMM_SIZE(icomm,nproc,ierr)
call MPI_COMM_RANK(icomm,iproc,ierr)
if (iproc == 1) then
xyz%x = 1
xyz%y = 2
xyz%z = 3
xyz%u = 4
xyz%v = 5
xyz%w = 6
xyz%uvw = (/10,10,10/)
else
xyz%x = 0
xyz%y = 0
xyz%z = 0
xyz%u = 0
xyz%v = 0
xyz%w = 0
xyz%uvw = (/0,0,0/)
endif
! Derived type
iblock(1) = 1
iblock(2) = 1
iblock(3) = 1
iblock(4) = 1
iblock(5) = 1
iblock(6) = 1
iblock(7) = 3
iblock(8) = 1
idisp(1) = 0 ! in bytes
idisp(2) = 4*1 ! in bytes
idisp(3) = 4*2 ! in bytes
idisp(4) = 4*3 ! in bytes
idisp(5) = 4*4 ! in bytes
idisp(6) = 4*5 ! in bytes
idisp(7) = 4*6 ! in bytes
idisp(8) = 4*9 ! in bytes
itype(1) = MPI_INTEGER
itype(2) = MPI_INTEGER
itype(3) = MPI_INTEGER
itype(4) = MPI_INTEGER
itype(5) = MPI_INTEGER
itype(6) = MPI_INTEGER
itype(7) = MPI_INTEGER
itype(8) = MPI_UB
call MPI_TYPE_STRUCT(8,iblock,idisp,itype,inewtype,ierr)
call MPI_TYPE_EXTENT(inewtype,iextent,ierr)
write(6,*)'newtype extent = ',iextent
call MPI_TYPE_COMMIT(inewtype,ierr)
itag = 1
dispGather = 0
do j = 1, 2
if ( j == 2 ) then
! Gather
call MPI_GATHERV(xyzBuffer,1,inewtype,xyz,1, dispGather,inewtype,0,icomm,ierr)
! Isend Irecv
if ( iproc == 1 ) then
call MPI_ISEND(xyz,1,inewtype,1,itag,icomm,isend,ierr)
write(6,*)'end send'
call MPI_WAIT(isend,istatus,ierr)
else if ( iproc == 0 ) then
call MPI_IRECV(xyz,1,inewtype,0,itag,icomm,irecv,ierr)
write(6,*)'end receive'
call MPI_WAIT(irecv,istatus,ierr)
end if
! Output
end if
call MPI_BARRIER(icomm,ierr)
if ( iproc == 0 )write(6,*)'iproc = ',iproc
if ( iproc == 0 ) write(6,*)xyz
call MPI_BARRIER(icomm,ierr)
if ( iproc == 1 )write(6,*)'iproc = ',iproc
if ( iproc == 1 ) write(6,*)xyz
end do
call MPI_FINALIZE(ierr)
end program type_derived_gather
当我使用MPI_ISEND和MPI_IRECV块运行时，程序挂起并且输出为：
iproc = 0
0 0 0 0 0 0 0 0 0
end receive
newtype extent = 36
iproc = 1
1 4 2 5 3 6 10 10 10
end send
当MPI_GATHER运行时，我收到带有输出的分段错误：
newtype extent = 36
iproc = 0
0 0 0 0 0 0 0 0 0
newtype extent = 36
iproc = 1
1 4 2 5 3 6 10 10 10
newtype extent = 36
newtype extent = 36
newtype extent = 36
newtype extent = 36
newtype extent = 36
newtype extent = 36
[west0302:17101] *** Process received signal ***
[west0302:17101] Signal: Segmentation fault (11)
[west0302:17101] Signal code: Address not mapped (1)
[west0302:17101] Failing at address: 0x7ff2c8d1ddc0
[west0302:17101] [ 0] /lib64/libpthread.so.0 [0x3d3540eb70]
[west0302:17101] [ 1] /lib64/libc.so.6(memcpy+0xe1) [0x3d3487c321]
[west0302:17101] [ 2] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib64/libmpi.so.0(ompi_convertor_unpack+0x153) [0x2acd5f392093]
[west0302:17101] [ 3] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib/openmpi/mca_pml_ob1.so(mca_pml_ob1_recv_request_progress+0x7d1) [0x2acd6423dd91]
[west0302:17101] [ 4] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib/openmpi/mca_pml_ob1.so [0x2acd6423a4c7]
[west0302:17101] [ 5] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib/openmpi/mca_btl_sm.so(mca_btl_sm_component_progress+0xde2) [0x2acd64ca81c2]
[west0302:17101] [ 6] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib/openmpi/mca_bml_r2.so(mca_bml_r2_progress+0x2a) [0x2acd6444504a]
[west0302:17101] [ 7] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib64/libopen-pal.so.0(opal_progress+0x4a) [0x2acd5f84a9ba]
[west0302:17101] [ 8] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib/openmpi/mca_pml_ob1.so(mca_pml_ob1_recv+0x2b5) [0x2acd64238565]
[west0302:17101] [ 9] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib/openmpi/mca_coll_basic.so(mca_coll_basic_gatherv_intra+0x14a) [0x2acd650bb37a]
[west0302:17101] [10] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib64/libmpi.so.0(MPI_Gatherv+0x1b0) [0x2acd5f3a4170]
[west0302:17101] [11] /n/sw/openmpi-1.2.5-gcc-4.1.2/lib64/libmpi_f77.so.0(mpi_gatherv__+0x134) [0x2acd5f142784]
[west0302:17101] [12] ./type_derived_gather.x(MAIN__+0x342) [0x401742]
[west0302:17101] [13] ./type_derived_gather.x(main+0xe) [0x403fee]
[west0302:17101] [14] /lib64/libc.so.6(__libc_start_main+0xf4) [0x3d3481d994]
[west0302:17101] [15] ./type_derived_gather.x [0x401349]
[west0302:17101] *** End of error message ***
答案 0 :(得分：3)
是的，您当然可以这样做：代码挂在MPI_Isend() / MPI_Irecv()上的问题是您发送/接收错误的进程;你希望1发送到0，0发送到1，而不是1发送到1和0从0接收.0永远不会收到幻像消息（因为它不存在），你就挂了。
if ( iproc == 1 ) then
call MPI_ISEND(xyz,1,inewtype,1,itag,icomm,isend,ierr)
write(6,*)'end send'
call MPI_WAIT(isend,istatus,ierr)
else if ( iproc == 0 ) then
call MPI_IRECV(xyz,1,inewtype,0,itag,icomm,irecv,ierr)
write(6,*)'end receive'
call MPI_WAIT(irecv,istatus,ierr)
end if
应该是
if ( iproc == 1 ) then
call MPI_ISEND(xyz,1,inewtype,0,itag,icomm,isend,ierr)
call MPI_WAIT(isend,istatus,ierr)
else if ( iproc == 0 ) then
call MPI_IRECV(xyz,1,inewtype,1,itag,icomm,irecv,ierr)
call MPI_WAIT(irecv,istatus,ierr)
end if
对于更大的问题，当然可以使用MPI_Type_create_struct()（注意，你应该在Fortran派生数据类型上使用这个更新的例程而不是MPI_Create_struct()。正如@elorenz指出的那样，计算手动偏移不仅单调乏味且容易出错，而且可能不正确;编译器有很大的自由来填充等等，以便有效地进行内存访问。在你的情况下，它可能会起作用，因为它是全部整数，但对于类型对于混合尺寸的领域，你会遇到麻烦。
正确处理方法是使用MPI_Get_address为您计算字段偏移量;下面是一个完整的例子。
program type_derived_gather
use iso_fortran_env
use mpi
implicit none
integer :: ierr
integer, parameter :: nfields=4
integer :: iblock(nfields)
integer(kind=MPI_ADDRESS_KIND) :: start, idisp(nfields)
integer :: itype(nfields)
integer :: inewtype
integer :: nproc, iproc
integer :: i
type :: newXYZ
integer :: id
real(kind=real64) :: x, y, z
end type
type(newXYZ), dimension(:), allocatable :: allxyzs
type(newXYZ) :: locxyz
call MPI_INIT(ierr)
call MPI_COMM_SIZE(MPI_COMM_WORLD,nproc,ierr)
call MPI_COMM_RANK(MPI_COMM_WORLD,iproc,ierr)
locxyz % x = 1.d0*iproc
locxyz % y = 2.d0*iproc
locxyz % z = 3.d0*iproc
locxyz % id = iproc
if (iproc == 0) allocate(allxyzs(nproc))
! everyone builds the type
iblock = 1
itype(1) = MPI_INTEGER
itype(2:4)= MPI_DOUBLE_PRECISION
call MPI_Get_address(locxyz, start, ierr)
call MPI_Get_address(locxyz%id, idisp(1), ierr)
call MPI_Get_address(locxyz%x, idisp(2), ierr)
call MPI_Get_address(locxyz%y, idisp(3), ierr)
call MPI_Get_address(locxyz%z, idisp(4), ierr)
idisp = idisp - start
call MPI_Type_create_struct(nfields,iblock,idisp,itype,inewtype,ierr)
call MPI_Type_commit(inewtype,ierr)
! Now gather the structs
print '(A,I3,A,I3,1X,3(F6.2,1X))', 'Rank ', iproc, ': locxyz = ', locxyz%id, locxyz%x, locxyz%y, locxyz%z
call MPI_Gather(locxyz, 1, inewtype, allxyzs, 1, inewtype, 0, MPI_COMM_WORLD, ierr)
if (iproc == 0) then
print '(A,I3,A)', 'Rank ', iproc, ' has -- '
do i=1, nproc
print '(A,I3,A,I3,1X,3(F6.2,1X))', ' ', i, ': ', allxyzs(i)%id, allxyzs(i)%x, allxyzs(i)%y, allxyzs(i)%z
enddo
deallocate(allxyzs)
end if
call MPI_FINALIZE(ierr)
end program type_derived_gather
答案 1 :(得分：0)
当然，您可以将MPI_Gather（或其他集合体）与派生数据类型一起使用。采用MPI_Datatype参数的任何MPI函数都可以与派生数据类型一起使用。如果你发布一个最小的例子，你如何构造和使用派生数据类型，我们可能会帮助更好。
答案 2 :(得分：0)
是的，它可以。但请确保在数据类型的定义中使用“序列”！否则，编译器可以在类型成员如何在内存中对齐方面获得一些自由。这可能会在复制缓冲区时导致一些混乱的数据。