问题与mpi_gather

我写了一个简单的代码来自己熟悉与mpi_gather：问题与mpi_gather

program main 
    use mpi 
    implicit none 
    integer :: myid, ierror, root_id, nprocs, ii 
    logical :: boolean 
    logical, dimension(:), allocatable :: all_booleans 

    call mpi_init(ierror) 
    call mpi_comm_rank(mpi_comm_world,myid,ierror) 
    call mpi_comm_size(mpi_comm_world, nprocs, ierror) 

    if(myid==0) then 
     print '(A9,I2)', "nprocs = ", nprocs 
     print*, "************************************************************" 
     print*, "From each processor" 
    end if 
    call mpi_barrier(mpi_comm_world,ierror) 

    boolean = .FALSE. 
    root_id = 10 
    if(myid==root_id) then 
     boolean = .TRUE. 
     allocate(all_booleans(0:nprocs-1)) 
    end if 

    print '(A7,I2,A11,L2)', "myid = ", myid, " boolean = ", boolean 
    call mpi_barrier(mpi_comm_world,ierror) 

    call mpi_gather(boolean, 1, mpi_logical, all_booleans, nprocs, mpi_logical, root_id,   & 
       & mpi_comm_world, ierror) 

    call mpi_barrier(mpi_comm_world,ierror) 
    if(myid==root_id) then 
     print*, "******************************************************************" 
     print *, "From the root processor, proC# : ", myid 
     do ii=0,nprocs-1 
      print '(A9,I2,A3,L2)', "processor ", ii, " = ", all_booleans(ii) 
     end do 
    end if 
    call mpi_barrier(mpi_comm_world,ierror) 

    if(myid==root_id) then 
     print*, "******************************************************************" 
     print*, "From each processor" 
    end if 
    call mpi_barrier(mpi_comm_world,ierror) 
    print '(A7,I2,A11,L2)', "myid = ", myid, " boolean = ", boolean 
    call mpi_barrier(mpi_comm_world,ierror) 

    call mpi_finalize(ierror) 

end program main

我使用mpiifort从ifort 14.0.2版本：

nprocs = 12 
************************************************************ 
From each processor 
myid = 0 boolean = F 
myid = 1 boolean = F 
myid = 3 boolean = F 
myid = 4 boolean = F 
myid = 5 boolean = F 
myid = 6 boolean = F 
myid = 7 boolean = F 
myid = 8 boolean = F 
myid = 9 boolean = F 
myid = 10 boolean = T 
myid = 11 boolean = F 
myid = 2 boolean = F 
****************************************************************** 
From the root processor, proC# :   10 
processor 0 = F 
processor 1 = T 
processor 2 = F 
processor 3 = T 
processor 4 = T 
processor 5 = T 
processor 6 = T 
processor 7 = T 
processor 8 = T 
processor 9 = T 
processor10 = T 
processor11 = T 
****************************************************************** 
From each processor 
myid = 0 boolean = F 
myid = 1 boolean = F 
myid = 2 boolean = F 
myid = 3 boolean = F 
myid = 4 boolean = F 
myid = 5 boolean = F 
myid = 6 boolean = F 
myid = 7 boolean = F 
myid = 8 boolean = F 
myid = 9 boolean = F 
myid = 10 boolean = T 
myid = 11 boolean = F

我设置变量boolean到.TRUE.仅用于根处理器（这里是proc 10）。然后我将所有boolean值收集到数组all_booleans到根处理器。当我输出all_booleans的值时，除了myid = 10之外，我预计会得到.FALSE.，但情况并非如此。我究竟做错了什么？

来源

2016-03-21 solalito

'调用mpi_gather（布尔值，1，mpi_logical，all_booleans，nprocs，mpi_logical，root_id，MPI_COMM_WORLD，IERROR）'是错误的。它应该读取'调用mpi_gather（布尔，1，mpi_logical，all_booleans，1，mpi_logical，root_id，mpi_comm_world，错误）' – Gilles

你有mpi_gather的参数有点不对。从http://www.mpich.org/static/docs/v3.2/www3/MPI_Gather.html为recv_count它说

recvcount 任何单一接收元素个数（整数，只有从根本显著）

注意一字单。因此，如果你改变你的呼叫

call mpi_gather(boolean, 1, mpi_logical, all_booleans, 1, mpi_logical, root_id,   & 
      & mpi_comm_world, ierror)

它为我工作：

Wot now? mpif90 gath.f90 
Wot now? mpirun -np 12 ./a.out 
nprocs = 12 
************************************************************ 
From each processor 
myid = 11 boolean = F 
myid = 3 boolean = F 
myid = 7 boolean = F 
myid = 8 boolean = F 
myid = 0 boolean = F 
myid = 4 boolean = F 
myid = 9 boolean = F 
myid = 10 boolean = T 
myid = 6 boolean = F 
myid = 2 boolean = F 
myid = 5 boolean = F 
myid = 1 boolean = F 
****************************************************************** 
From the root processor, proC# :   10 
processor 0 = F 
processor 1 = F 
processor 2 = F 
processor 3 = F 
processor 4 = F 
processor 5 = F 
processor 6 = F 
processor 7 = F 
processor 8 = F 
processor 9 = F 
processor10 = T 
processor11 = F 
****************************************************************** 
From each processor 
myid = 6 boolean = F 
myid = 11 boolean = F 
myid = 0 boolean = F 
myid = 2 boolean = F 
myid = 1 boolean = F 
myid = 3 boolean = F 
myid = 7 boolean = F 
myid = 9 boolean = F 
myid = 5 boolean = F 
myid = 10 boolean = T 
myid = 4 boolean = F 
myid = 8 boolean = F

来源

2016-03-21 12:00:01

是不是有点多余？即我期望'sendcount'和'recvcount'将始终是相同的 – solalito

数据类型不一定是相同的。是的，疯狂在于这条路线，但它是被允许的......对于基本类型并不是那么有趣，但是当涉及派生类型时，它可能有其用途。 –

@solalito，双方的基本数据类型（也称为类型签名）的计数和排序必须匹配。但是这些基本数据类型可以不同地分组为例如派生数据类型。 –

问题与mpi_gather

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