MPI_TYPE_GET_CONTENTS(3)			     Open MPI				  MPI_TYPE_GET_CONTENTS(3)

MPI_Type_get_contents — Returns information about arguments used in creation of a data type.

SYNTAX
   C Syntax
	  #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[])

   Fortran Syntax
	  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(*)

   Fortran 2008 Syntax
	  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

INPUT PARAMETERS
       • datatype: Data type to access (handle).

       • max_integers: Number of elements in array_of_integers (nonnegative integer).

       • max_addresses: Number of elements in array_of_addresses (nonnegative integer).

       • max_datatypes: Number of elements in array_of_datatypes (nonnegative integer).

OUTPUT PARAMETERS
       • array_of_integers: Contains integer arguments used in constructing datatype (array of integers).

       • array_of_addresses: Contains address arguments used in constructing datatype (array of integers).

       • array_of_datatypes: Contains data-type arguments used in constructing datatype (array of integers).

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

DESCRIPTION
       For  the	 given data type, MPI_Type_get_envelope <#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  datatype	 must  be  a  predefined  unnamed or a derived data type. The call is erroneous if
       datatype is a predefined named data type.

       The values given for max_integers, max_addresses, and max_datatypes must be at least as large as the  value
       returned	   in	 num_integers,	  num_addresses,    and	  num_datatypes,   respectively,   in	the   call
       :ref:`MPI_Type_get_envelope` for the same datatype argument.

       The data types returned in array_of_datatypes are handles to data-type objects that are equivalent  to  the
       data types used in the original construction call. If these were derived data types, then the returned data
       types  are  new	data-type  objects,  and  the  user  is	 responsible  for  freeing  these  datatypes  with
       :ref:`MPI_Type_free`. If these were predefined data types, then the returned data type  is  equal  to  that
       (constant) predefined data type and cannot be freed.

       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-real>,	     MPI_Type_create_f90_integer	<#
       mpi-type-create-f90-integer>, or	 MPI_Type_create_f90_complex  <#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 MPI Standard <https://www.mpi-forum.org/docs/>, 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.

ERRORS
       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>/MPI_Init_thread <#mpi-init-thread>,
       after MPI_Finalize <#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 <#
       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>/MPI_Comm_spawn_multiple	<#
       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 <#mpi-abort> was called on that communicator. If called
	 on  a window or file, acts as if MPI_Abort <#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	<#mpi-comm-create-errhandler>	  then	   MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	 <#mpi-file-create-errhandler>	   then	    MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

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

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

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

       See also:

	  • MPI_Type_get_envelope <#mpi-type-get-envelope>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				  MPI_TYPE_GET_CONTENTS(3)
