[mpich-discuss] MPICH does not work for quad precision

[Jiancang Zhuang]

I have found that the fortran version mpi_reduce does not work for real*18.
This can be shown by the following program. I have not test the C version
of mpi_reduce.


c-----------------------Fortran code begins -----------------------------
      implicit real*8 (a-h, o-z)
      include 'mpif.h'
      real*16 h1, h


      call mpi_init(ierr)
      call mpi_comm_size(mpi_comm_world, nprocs, ierr)
      call mpi_comm_rank(mpi_comm_world, myrank, ierr)


      h1 = (myrank+4) *2.00000000000000
      write(*,'(''before reduce --'', i4,2f12.8)')myrank, h1,h


      call mpi_reduce(h1,h,1,mpi_long_double,mpi_sum,0,
     &    mpi_comm_world,ierr)
      write(*,'(''after reduce --'',i4,2f12.8)')myrank, h1,h

      call mpi_bcast(h,1,mpi_long_double,0,
     &    mpi_comm_world,ierr)

      write(*,'(''bcastvalue -- '',i4,2f12.8)')myrank, h1,h

      call mpi_finalize(ierr)
       end

c-----------------------Fortran code begins -----------------------------


$ mpif77 a.f -o a.out
$ mpirun -np 3 ./a.out
before reduce --   1 10.00000000  0.00000000
after reduce --   1 10.00000000  0.00000000
before reduce --   2 12.00000000  0.00000000
before reduce --   0  8.00000000  0.00000000
after reduce --   2 12.00000000  0.00000000
after reduce --   0  8.00000000  8.00000000
bcastvalue --    0  8.00000000  8.00000000
bcastvalue --    1 10.00000000  8.00000000
bcastvalue --    2 12.00000000  8.00000000
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