# MPI_Intercomm_create_from_groups

Create an intercommuncator from local and remote groups

## Synopsis

    #ifdef ENABLE_QMPI
    #ifndef MPICH_MPI_FROM_PMPI
    int QMPI_Intercomm_create_from_groups(QMPI_Context context, int tool_id, MPI_Group local_group,
                                          int local_leader, MPI_Group remote_group, int remote_leader,
                                          const char *stringtag, MPI_Info info,
                                          MPI_Errhandler errhandler,
                                          MPI_Comm *newintercomm) MPICH_API_PUBLIC

## Input Parameters

local_group
  local group (handle)
local_leader
  rank of local group leader in local_group (integer)
remote_group
  remote group, significant only at local_leader (handle)
remote_leader
  rank of remote group leader in remote_group, significant only at local_leader (integer)
stringtag
  unique idenitifier for this operation (string)
info
  info object (handle)
errhandler
  error handler to be attached to new inter-communicator (handle)

## Output Parameters

newintercomm
  new inter-communicator (handle)

## Thread and Interrupt Safety

This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as `malloc` or other non-MPICH runtime routines that are themselves not interrupt-safe.

## Notes for Fortran

All MPI routines in Fortran (except for `MPI_WTIME` and `MPI_WTICK`) have an additional argument `ierr` at the end of the argument list. `ierr` is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the `call` statement.

All MPI objects (e.g., `MPI_Datatype`, `MPI_Comm`) are of type `INTEGER` in Fortran.

## Errors

All MPI routines (except `MPI_Wtime` and `MPI_Wtick`) return an error value; C routines as the value of the function and Fortran routines in the last argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with `MPI_Comm_set_errhandler` (for communicators), `MPI_File_set_errhandler` (for files), and `MPI_Win_set_errhandler` (for RMA windows). The MPI-1 routine `MPI_Errhandler_set` may be used but its use is deprecated. The predefined error handler `MPI_ERRORS_RETURN` may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible.

MPI_SUCCESS
  No error; MPI routine completed successfully.

MPI_ERR_ARG
  Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., `MPI_ERR_RANK`).

MPI_ERR_GROUP
  Null or invalid group passed to function.

MPI_ERR_INFO
  Invalid Info

MPI_ERR_OTHER
  Other error; use `MPI_Error_string` to get more information about this error code.