MPI_CART_MAP(3)					     Open MPI					   MPI_CART_MAP(3)

MPI_Cart_map — Maps process to Cartesian topology information.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Cart_map(MPI_Comm comm, int ndims, const int dims[],
	      const int periods[], int *newrank)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'

	  MPI_CART_MAP(COMM, NDIMS, DIMS, PERIODS, NEWRANK, IERROR)
	      INTEGER COMM, NDIMS, DIMS(*), NEWRANK, IERROR
	      LOGICAL PERIODS(*)

   Fortran 2008 Syntax
	  USE mpi_f08

	  MPI_Cart_map(comm, ndims, dims, periods, newrank, ierror)
	      TYPE(MPI_Comm), INTENT(IN) :: comm
	      INTEGER, INTENT(IN) :: ndims, dims(ndims)
	      LOGICAL, INTENT(IN) :: periods(ndims)
	      INTEGER, INTENT(OUT) :: newrank
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • comm : Input communicator (handle).

       • ndims : Number of dimensions of Cartesian structure (integer).

       •

	 dims (Integer array of size ndims specifying the number of processes)
		in each coordinate direction.

       •

	 periods (Logical array of size ndims specifying the periodicity)
		specification in each coordinate direction.

OUTPUT PARAMETERS
       •

	 newrank (Reordered rank of the calling process; MPI_UNDEFINED if)
		calling process does not belong to grid (integer).

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

DESCRIPTION
       MPI_Cart_map  and  MPI_Graph_map <#mpi-graph-map> can be used to implement all other topology functions. In
       general they will not be called by the user directly, unless he	or  she	 is  creating  additional  virtual
       topology	 capability  other than that provided by MPI. MPI_Cart_map computes an “optimal” placement for the
       calling process on the physical machine. A possible implementation of this function is to always return the
       rank of the calling process, that is, not to perform any reordering.

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_Graph_map <#mpi-graph-map>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					   MPI_CART_MAP(3)
