MPI_Type_struct − Creates a struct data type -- use of this routine is deprecated.
#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) |
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 |
count |
Number of blocks (integer) also number of entries in arrays array_of_types, array_of_displacements, and array_of_blocklengths. |
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).
newtype |
New datatype (handle). |
|||
IERROR |
Fortran only: Error status (integer). |
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 generalizes 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.
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Standard originally made vague statements about padding and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 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);
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
);
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ functions 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.
MPI_Type_create_struct
MPI_Type_create_hindexed