#include "mpi.h" int MPI_Intercomm_merge ( MPI_Comm comm, int high, MPI_Comm *comm_out )
|high||Used to order the groups of the two intracommunicators within comm
when creating the new communicator.
All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.
1) Allocate two contexts 2) Local and remote group leaders swap high values 3) Determine the high value. 4) Merge the two groups and make the intra-communicator
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_Errhandler_set; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error.