[mpich-discuss] MPI_FILE_read and derived types in fortran.

[Scot Breitenfeld]

Hi,

I created a file in fortran using (which I compiled with mpif90):

PROGRAM writeUstream
  
  IMPLICIT NONE
  INTEGER :: i, ii
  INTEGER, DIMENSION(1:3,1:25) :: buf

  OPEN(UNIT=11, FILE="ustream.demo", FORM="unformatted", STATUS="UNKNOWN", ACCESS="STREAM")

  ii = 1

  DO i=1, 25
     buf(1,i) = ii
     buf(2,i) = ii+1
     buf(3,i) = ii+2
     WRITE(11) buf(1:3,i)
     ii = ii + 3
  ENDDO
  CLOSE(UNIT=11)

END PROGRAM writeUstream

And I’ve made a simple program to read the file (on the same machine) using MPI_FILE_read:

PROGRAM struct

  USE mpi

  IMPLICIT NONE

  INTEGER, PARAMETER :: NELEM = 2
  INTEGER :: numtasks, rank, source, dest, tag, i,  ierr 
  INTEGER :: stat(MPI_STATUS_SIZE) 
  INTEGER :: fh
  INTEGER :: status
  INTEGER(kind=MPI_OFFSET_KIND) :: disp

  INTEGER, DIMENSION(1:3) :: iiaux

  TYPE Particle
     SEQUENCE
     INTEGER, DIMENSION(1:3) :: indx
  END TYPE Particle

  TYPE(Particle), DIMENSION(1:nelem) ::  particles
  INTEGER particletype, oldtypes(1:1), blockcounts(1:1), offsets(1:1), extent 

  CALL MPI_INIT(ierr)
  CALL MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
  CALL MPI_COMM_SIZE(MPI_COMM_WORLD, numtasks, ierr)

  !  Setup description of the 3 MPI_INTEGERS fields x, y, z
  offsets(1) = 0
  oldtypes(1) = MPI_INTEGER
  blockcounts(1) = 3

  !  Now define structured TYPE and commit it  
  CALL MPI_TYPE_STRUCT(1, blockcounts, offsets, oldtypes, particletype, ierr)
  CALL MPI_TYPE_COMMIT(particletype, ierr)

  CALL MPI_File_open(MPI_COMM_WORLD, "ustream.demo", MPI_MODE_RDONLY, MPI_INFO_NULL, fh, ierr)
  
  disp = 0

  CALL MPI_File_set_view(fh, disp, MPI_INTEGER, particletype, "native", MPI_INFO_NULL, ierr)

  particles(1:nelem)%indx = -1

  CALL MPI_File_read(fh, particles, nelem, particletype, status, ierr) 

  PRINT*,"derived type"
  DO i=1,nelem
     PRINT*,particles(i)%indx
  ENDDO

  CALL MPI_File_close(fh, ierr)

  CALL MPI_File_open(MPI_COMM_WORLD, "ustream.demo", MPI_MODE_RDONLY, &
                  MPI_INFO_NULL, fh, ierr)

  CALL MPI_FILE_read(fh,iiaux,3,MPI_INTEGER,status,ierr)

  PRINT*,"No derived type"

  PRINT*,iiaux
  CALL MPI_FILE_read(fh,iiaux,3,MPI_INTEGER,status,ierr)
  PRINT*,iiaux

  CALL MPI_File_close(fh, ierr)

  CALL MPI_FINALIZE(ierr) 
END PROGRAM struct


When I run this program to read the file using just one process, the first two integers of the derived type are not correct, but all the remaining values are correct. All the values when reading them into an integer array is correct. Here is the output:

 derived type
          24           0           3
           4           5           6
 No derived type
           1           2           3
           4           5           6

I don’t get any error from the MPI calls and I used gcc 4.8.1 to compile mpich 3.0.4 on Linux  2.6.18-308.13.1.el5PAE #1 SMP Tue Aug 21 17:50:26 EDT 2012 i686 i686 i386 GNU/Linux
I not exactly sure what is going on.

Thanks,
Scot