#include "mpi.h" int MPI_Type_indexed( int count, int blocklens[], int indices[], MPI_Datatype old_type, MPI_Datatype *newtype )
count  number of blocks  also number of entries in indices and blocklens
 
blocklens  number of elements in each block (array of nonnegative integers)
 
indices  displacement of each block in multiples of old_type (array of
integers)
 
old_type  old datatype (handle)

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.
The indices are displacements, and are based on a zero origin. A common error is to do something like to following
integer a(100) integer blens(10), indices(10) do i=1,10 blens(i) = 1 10 indices(i) = 1 + (i1)*10 call MPI_TYPE_INDEXED(10,blens,indices,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 indices 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 indices into a Fortran array, consider declaring the Fortran array with a zero origin
integer a(0:99)
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_Errhandler_set; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error.
Location:type_ind.c