MPI_Type_struct(3) Open MPI MPI_Type_struct(3)NAMEMPI_Type_struct - Creates a struct data type -- use of this routine is
deprecated.
SYNTAXC Syntax
#include <mpi.h>
int MPI_Type_struct(int count, int *array_of_blocklengths,
MPI_Aint *array_of_displacements, MPI_Datatype *array_of_types,
MPI_Datatype *newtype)
Fortran Syntax
INCLUDE 'mpif.h'
MPI_TYPE_STRUCT(COUNT, ARRAY_OF_BLOCKLENGTHS,
ARRAY_OF_DISPLACEMENTS, ARRAY_OF_TYPES,
NEWTYPE, IERROR)
INTEGER COUNT, ARRAY_OF_BLOCKLENGTHS(*)
INTEGER ARRAY_OF_DISPLACEMENTS(*)
INTEGER ARRAY_OF_TYPES(*), NEWTYPE, IERROR
INPUT PARAMETERS
count Number of blocks (integer) also number of entries in arrays
array_of_types, array_of_displacements, and array_of_block‐
lengths.
array_of_blocklengths
Number of elements in each block (array).
array_of_displacements
Byte displacement of each block (array).
array_of_types
Type of elements in each block (array of handles to datatype
objects).
OUTPUT PARAMETERS
newtype New datatype (handle).
IERROR Fortran only: Error status (integer).
DESCRIPTION
Note that use of this routine is deprecated as of MPI-2. Use
MPI_Type_create_struct instead.
This deprecated routine is not available in C++.
MPI_Type_struct is the most general type constructor. It further gener‐
alizes MPI_Type_hindexed in that it allows each block to consist of
replications of different datatypes.
Example: Let type1 have type map
{(double, 0), (char, 8)}
with extent 16. Let B = (2, 1, 3), D = (0, 16, 26), and T = (MPI_FLOAT,
type1, MPI_CHAR). Then a call to MPI_Type_struct(3, B, D, T, newtype)
returns a datatype with type map
{(float, 0), (float,4), (double, 16), (char, 24),
(char, 26), (char, 27), (char, 28)}
That is, two copies of MPI_FLOAT starting at 0, followed by one copy of
type1 starting at 16, followed by three copies of MPI_CHAR, starting at
26. (We assume that a float occupies 4 bytes.)
For more information, see section 3.12.1 of the MPI-1.1 Standard.
NOTES
If an upperbound is set explicitly by using the MPI datatype MPI_UB,
the corresponding index must be positive.
The MPI-1 Standard originally made vague statements about padding and
alignment; this was intended to allow the simple definition of struc‐
tures 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);
defining the extent of a datatype as including an epsilon, which 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 );
ERRORS
Almost all MPI routines return an error value; C routines as the value
of the function and Fortran routines in the last argument. C++ func‐
tions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; 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.
SEE ALSO
MPI_Type_create_struct
MPI_Type_create_hindexed
1.7.4 Feb 04, 2014 MPI_Type_struct(3)
