int MPI_Type_indexed(int count, const int *array_of_blocklengths, const int *array_of_displacements, MPI_Datatype oldtype, MPI_Datatype * newtype)
This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.
The array_of_displacements are displacements, and are based on a zero origin. A common error is to do something like to following
integer a(100) integer array_of_blocklengths(10), array_of_displacements(10) do i=1,10 array_of_blocklengths(i) = 1 10 array_of_displacements(i) = 1 + (i-1)*10 call MPI_TYPE_INDEXED(10,array_of_blocklengths,array_of_displacements,MPI_INTEGER,newtype,ierr) call MPI_TYPE_COMMIT(newtype,ierr) call MPI_SEND(a,1,newtype,...)expecting this to send "a(1),a(11),..." because the array_of_displacements have values "1,11,...". Because these are displacements from the beginning of "a", it actually sends "a(1+1),a(1+11),...".
If you wish to consider the displacements as array_of_displacements into a Fortran array, consider declaring the Fortran array with a zero origin
All MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.