#include "mpi.h"
int MPI_Type_struct( count, blocklens, indices, old_types, newtype )
int count;
int blocklens[];
MPI_Aint indices[];
MPI_Datatype old_types[];
MPI_Datatype *newtype;
The MPI standard originally made vague statements about padding and alignment; this was intended to allow the simple definition of structures that could be sent with a count greater than one. For example,
struct { int a; char b; } foo;
may have sizeof(foo) > sizeof(int) + sizeof(char); for example,
sizeof(foo) == 2*sizeof(int). The initial version of the MPI standard
defined the extent of a datatype as including an epsilon that would have
allowed an implementation to make the extent an MPI datatype
for this structure equal to 2*sizeof(int). However, since different systems
might define different paddings, a clarification to the standard made epsilon
zero. Thus, if you define a structure datatype and wish to send or receive
multiple items, you should explicitly include an MPI_UB entry as the
last member of the structure. For example, the following code can be used
for the structure foo
blen[0] = 1; indices[0] = 0; oldtypes[0] = MPI_INT;
blen[1] = 1; indices[1] = &foo.b - &foo; oldtypes[1] = MPI_CHAR;
blen[2] = 1; indices[2] = sizeof(foo); oldtypes[2] = MPI_UB;
MPI_Type_struct( 3, blen, indices, oldtypes, &newtype );
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.
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_struct.c