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