MPI_TYPE_INDEXED(3)				     Open MPI				       MPI_TYPE_INDEXED(3)

MPI_Type_indexed, MPI_Type_create_hindexed <#mpi-type-create-hindexed> - Creates an indexed datatype.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Type_indexed(int count, const int array_of_blocklengths[],
	       const int array_of_displacements[], MPI_Datatype oldtype,
	       MPI_Datatype *newtype)

	  int MPI_Type_create_hindexed(int count,
	       const int array_of_blocklengths[],
	       const MPI_Aint array_of_displacements[], MPI_Datatype oldtype,
	       MPI_Datatype *newtype)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_TYPE_INDEXED(COUNT, ARRAY_OF_BLOCKLENGTHS,
		       ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR)
	       INTEGER COUNT, ARRAY_OF_BLOCKLENGTHS(*)
	       INTEGER ARRAY_OF_DISPLACEMENTS(*), OLDTYPE, NEWTYPE
	       INTEGER IERROR

	  MPI_TYPE_CREATE_HINDEXED(COUNT, ARRAY_OF_BLOCKLENGTHS,
		       ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR)
	       INTEGER COUNT, ARRAY_OF_BLOCKLENGTHS(*)
	       INTEGER OLDTYPE, NEWTYPE
	       INTEGER(KIND=MPI_ADDRESS_KIND) ARRAY_OF_DISPLACEMENTS(*)
	       INTEGER IERROR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Type_indexed(count, array_of_blocklengths, array_of_displacements,
		       oldtype, newtype, ierror)
	       INTEGER, INTENT(IN) :: count, array_of_blocklengths(count),
	       array_of_displacements(count)
	       TYPE(MPI_Datatype), INTENT(IN) :: oldtype
	       TYPE(MPI_Datatype), INTENT(OUT) :: newtype
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

	  MPI_Type_create_hindexed(count, array_of_blocklengths,
		       array_of_displacements, oldtype, newtype, ierror)
	       INTEGER, INTENT(IN) :: count, array_of_blocklengths(count)
	       INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) ::
	       array_of_displacements(count)
	       TYPE(MPI_Datatype), INTENT(IN) :: oldtype
	       TYPE(MPI_Datatype), INTENT(OUT) :: newtype
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • count:	 Number	 of  blocks  —	also number of entries in array_of_displacements and array_of_blocklengths
	 (nonnegative integer).

       • array_of_blocklengths: Number of elements per block (array of nonnegative integers).

       • array_of_displacements: Displacement for each block, in multiples of oldtype extent for  MPI_Type_indexed
	 and  bytes  for  MPI_Type_create_hindexed  (array  of integer for MPI_TYPE_INDEXED, array of MPI_Aint for
	 MPI_TYPE_CREATE_HINDEXED).

       • oldtype: Old datatype (handle).

OUTPUT PARAMETERS
       • newtype: New datatype (handle).

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

DESCRIPTION
       The function MPI_Type_indexed allows replication of an old datatype into a sequence of blocks  (each  block
       is a concatenation of the old datatype), where each block can contain a different number of copies and have
       a different displacement. All block displacements are multiples of the old data type’s extent.

       Example: Let oldtype have type map {(double, 0), (char, 8)}, with extent 16. Let B = (3, 1) and let D = (4,
       0). A call to MPI_Type_indexed(2, B, D, oldtype, newtype) returns a datatype with type map

	  {(double, 64), (char, 72), (double, 80), (char, 88),
	  (double, 96), (char, 104),
	  (double, 0), (char, 8)}

       That  is,  three	 copies	 of  the  old  type starting at displacement 4 x 16 = 64, and one copy starting at
       displacement 0.

       In general, assume that oldtype has type map

	  {(type(0), disp(0)), ..., (type(n-1), disp(n-1))},
       with extent ex. Let B be the array_of_blocklength argument and D be
       the array_of_displacements argument. The newly created datatype has

	  n x S ^count-1
	      i = 0	      B[i]  entries:

	      {(type(0), disp(0) + D[0]* ex), ...,
	      (type(n-1), disp(n-1) + D[0]* ex), ...,
	      (type(0), disp(0) + (D[0] + B[0]-1)* ex), ...,
	      (type(n-1), disp(n-1) + (D[0]+ B[0]-1)* ex), ...,
	      (type(0), disp(0) + D[count-1]* ex), ...,
	      (type(n-1), disp(n-1) + D[count-1]* ex), ...,
	      (type(0), disp(0) +  (D[count-1] + B[count-1] -1)* ex), ...,
	      (type(n-1), disp(n-1) + (D[count-1] + B[count-1] -1)* ex)}

       A call to MPI_Type_vector(count, blocklength,  stride,  oldtype,	 newtype)  is  equivalent  to  a  call	to
       MPI_Type_indexed(count, B, D, oldtype, newtype) where

	      D[j] = j * stride, j = 0,..., count-1

	  and

	      B[j] = blocklength, j = 0, .., count-1

       The  function MPI_Type_create_hindexed <#mpi-type-create-hindexed> is identical to MPI_Type_indexed, except
       that block displacements in array_of_displacements are specified in bytes, rather than in multiples of  the
       oldtype extent.

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_hindexed <#mpi-type-hindexed>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				       MPI_TYPE_INDEXED(3)
