4 Combining Frameworks

This section describes how to combine multiple frameworks in a single application. You might want to do this, for example, to use AMPI communication inside a finite element method solver.

You specify how you want the frameworks to be combined by writing a special setup routine that runs when the program starts. The setup routine must be named TCHARM_User_setup. If you declare a user setup routine, the standard framework setup routines (such as the FEM framework's init routine) are bypassed, and you do all the setup in the user setup routine.

The setup routine creates a set of threads and then attaches frameworks to the threads. Several different frameworks can be attached to one thread set, and there can be several sets of threads; however, the most frameworks cannot be attached more than once to single set of threads. That is, a single thread cannot have two attached AMPI frameworks, since the MPI_COMM_WORLD for such a thread would be indeterminate.

void TCHARM_Create(int nThreads, TCharmThreadStartFn thread_fn)
SUBROUTINE TCHARM_Create(nThreads,thread_fn)
INTEGER, INTENT(in) :: nThreads
SUBROUTINE :: thread_fn

Create a new set of TCHARM threads of the given size. The threads will execute the given function, which is normally your user code. You should call TCHARM_Get_num_chunks() to get the number of threads from the command line. This routine can only be called from your TCHARM_User_setup routine.

You then attach frameworks to the new threads. The order in which frameworks are attached is irrelevant, but attach commands always apply to the current set of threads.

To attach a chare array to the TCHARM array, use:

CkArrayOptions TCHARM_Attach_start(CkArrayID *retTCharmArray,int *retNumElts)
This function returns a CkArrayOptions object that will bind your chare array to the TCHARM array, in addition to returning the TCHARM array proxy and number of elements by reference. If you are using frameworks like AMPI, they will automatically attach themselves to the TCHARM array in their initialization routines.