C Syntax

       2003-2025, The Open MPI Community

                                                  Jun 07, 2025                          MPI_TYPE_GET_CONTENTS(3)

       For  the  given  data  type,  MPI_Type_get_envelope  returns  information on the number and type of input
       arguments used in the call that created the data type. The number-of-arguments  values  returned  can  be
       used  to  provide  sufficiently large arrays in the decoding routine MPI_Type_get_contents. This call and
       the meaning of the returned  values  is  described  below.  The  combiner  reflects  the  MPI  data  type
       constructor call that was used in creating datatype.

       The  parameter  datatypemustbeapredefinedunnamedoraderiveddatatype.Thecalliserroneousifdatatypeisapredefinednameddatatype.

       The values given for max_integers,max_addresses,andmax_datatypesmustbeatleastaslargeasthevaluereturnedinnum_integers,num_addresses,andnum_datatypes,respectively,inthecall:ref:`MPI_Type_get_envelope`forthesamedatatypeargument.

       The data types returned in array_of_datatypesarehandlestodata-typeobjectsthatareequivalenttothedatatypesusedintheoriginalconstructioncall.Ifthesewerederiveddatatypes,thenthereturneddatatypesarenewdata-typeobjects,andtheuserisresponsibleforfreeingthesedatatypeswith:ref:`MPI_Type_free`.Ifthesewerepredefineddatatypes,thenthereturneddatatypeisequaltothat(constant)predefineddatatypeandcannotbefreed.

       The  committed  state of returned derived data types is undefined, that is, the data types may or may not
       be committed. Furthermore, the content of attributes of returned data types is undefined.

       Note that MPI_Type_get_contents can be invoked with a  data-type  argument  that  was  constructed  using
       MPI_Type_create_f90_real,   MPI_Type_create_f90_integer,   or   MPI_Type_create_f90_complex  (an  unnamed
       predefined data type). In such a case, an empty array_of_datatypes is returned.

       In the legacy MPI-1 datatype constructor calls, the address arguments in Fortran are of type INTEGER.  In
       subsequent    versions    of    the    MPIStandard,    the    address    arguments    are   of   type
       INTEGER(KIND=MPI_ADDRESS_KIND). The call MPI_Type_get_contents returns all addresses in  an  argument  of
       type  INTEGER(KIND=MPI_ADDRESS_KIND).  This  is  true  even  if  the old MPI-1 calls were used. Thus, the
       location of values returned can be thought of as being returned  by  the  C  bindings.  It  can  also  be
       determined  by  examining  the current MPI calls for datatype constructors for the deprecated MPI-1 calls
       that involve addresses.

       Almost all MPI routines return an error value; C routines as  the  return  result  of  the  function  and
       Fortran routines in the last argument.

       Before  the  error  value  is  returned,  the current MPI error handler associated with the communication
       object (e.g., communicator, window, file) is called.  If no communication object is associated  with  the
       MPI  call,  then  the call is considered attached to MPI_COMM_SELF and will call the associated MPI error
       handler.  When  MPI_COMM_SELF  is  not  initialized   (i.e.,   before   MPI_Init/MPI_Init_thread,   after
       MPI_Finalize,  or  when using the Sessions Model exclusively) the error raises the initial error handler.
       The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF  when  using
       the  World  model,  or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/‐
       MPI_Comm_spawn_multiple.  If no other appropriate error handler has been set, then the  MPI_ERRORS_RETURN
       error  handler  is  called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all
       other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or session. When
         called on a communicator, it acts as if MPI_Abort was called on  that  communicator.  If  called  on  a
         window  or file, acts as if MPI_Abort was called on a communicator containing the group of processes in
         the corresponding window or file. If called on a session, aborts only the local process.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       • MPI_File_create_errhandler then MPI_File_set_errhandler

       • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init

       • MPI_Win_create_errhandler then MPI_Win_set_errhandler

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPImanpage for a full list of MPIerrorcodes.

       See the Error Handling section of the MPI-3.1 standard for more information.

       SEEALSO:

          • MPI_Type_get_envelope

       • datatype: Data type to access (handle).

       • max_integers: Number of elements in array_of_integers(nonnegativeinteger).

       • max_addresses: Number of elements in array_of_addresses(nonnegativeinteger).

       • max_datatypes: Number of elements in array_of_datatypes(nonnegativeinteger).

       • array_of_integers: Contains integer arguments used in constructing datatype(arrayofintegers).

       • array_of_addresses: Contains address arguments used in constructing datatype(arrayofintegers).

       • array_of_datatypes: Contains data-type arguments used in constructing datatype(arrayofintegers).

       • ierror: Fortran only: Error status (integer).

CSyntax
          #include <mpi.h>

          int MPI_Type_get_contents(MPI_Datatype datatype, int max_integers,
               int max_addresses, int max_datatypes, int array_of_integers[], MPI_Aint array_of_addresses[], MPI_Datatype array_of_datatypes[])

   FortranSyntax
          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_TYPE_GET_CONTENTS(DATATYPE, MAX_INTEGERS, MAX_ADDRESSES,
                       MAX_DATATYPES, ARRAY_OF_INTEGERS, ARRAY_OF_ADDRESSES,
                       ARRAY_OF_DATATYPES, IERROR)
               INTEGER DATATYPE, MAX_INTEGERS, MAX_ADDRESSES, MAX_DATATYPES
               INTEGER ARRAY_OF_INTEGERS(*), ARRAY_OF_DATATYPES(*), IERROR
               INTEGER(KIND=MPI_ADDRESS_KIND) ARRAY_OF_ADDRESSES(*)

   Fortran2008Syntax
          USE mpi_f08
          MPI_Type_get_contents(datatype, max_integers, max_addresses, max_datatypes,
               array_of_integers, array_of_addresses, array_of_datatypes,
                       ierror)
               TYPE(MPI_Datatype), INTENT(IN) :: datatype
               INTEGER, INTENT(IN) :: max_integers, max_addresses, max_datatypes
               INTEGER, INTENT(OUT) :: array_of_integers(max_integers)
               INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) ::
               array_of_addresses(max_addresses)
               TYPE(MPI_Datatype), INTENT(OUT) :: array_of_datatypes(max_datatypes)
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror