MPI_Type_get_envelope(3)

NAME
     MPI_Type_get_envelope - Returns the number and type of input arguments

SYNOPSIS
     C:

          #include "mpi.h"

          int MPI_Type_get_envelope(MPI_Datatype datatype, int *num_integers,
          int *num_addresses, int *num_datatypes, int *combiner)


     Fortran:

          INCLUDE "mpif.h" (or USE MPI)

          INTEGER datatype, num_integers, num_addresses,
          num_datatypes, combiner, ierror

          CALL MPI_TYPE_GET_ENVELOPE(datatype, num_integers, num_addresses,
          num_datatypes, combiner, ierror)


DESCRIPTION
     For a specified data type, MPI_Type_get_envelope returns information on
     the number and type of input arguments that were used in the call that
     created the data type. The returned values can be used to provide
     sufficiently large arrays in the decoding routine, MPI_Type_get_contents.
     MPI_Type_get_envelope accepts the following arguments:

     datatype            Specifies the data type to be accessed (handle)

     num_integers        Returns the number of input integers used in the call
                         that constructs the combiner (nonnegative integer)

     num_addresses       Returns the number of input addresses used in the
                         call that constructs the combiner (nonnegative
                         integer)

     num_datatypes       Returns the number of input data types used in the
                         call that constructs the combiner (nonnegative
                         integer)

     combiner            Reflects the MPI data type constructor call that was
                         used in creating the data type (state)

     ierror              Specifies the return code value for successful
                         completion, which is in MPI_SUCCESS.  MPI_SUCCESS is
                         defined in the mpif.h file.
     By requiring that the combiner reflect the constructor used in the
     creation of the data type, the decoded information can be used to
     effectively recreate the calling sequence used in the original creation.
     One call is effectively the same as another when the information obtained
     from MPI_Type_get_contents can be used with either to produce the same
     outcome. In some MPI implementations, C calls, MPI_Type_hindexed and
     MPI_Type_create_hindexed, are always effectively the same, while the
     Fortran call, MPI_TYPE_HINDEXED, is different from either of these.

     The decoded information keeps track of data type duplications. This is
     important for distinguishing between a predefined data type and a
     duplicate of a predefined data type. The former is a constant object that
     cannot be freed; the latter is a derived data type that can be freed.

     The actual arguments used in the creation call for a data type can be
     obtained from the MPI_Type_get_contents call.

SEE ALSO
     MPI_File_open(3), MPI_Type_get_contents(3)