Communicator Management

int Comm.Size()

returns:

number of processors in the group of this communicator

Size of group of this communicator. Java binding of the MPI operation MPI_COMM_SIZE.

int Comm.Rank()

returns:

rank of the calling process in the group of this communicator

Rank of this process in group of this communicator. Java binding of the MPI operation MPI_COMM_RANK.

static int Comm.Compare(Comm comm1, Comm comm2)

comm1	first communicator
comm2	second communicator
returns:	result

Compare two communicators. Java binding of the MPI operation MPI_COMM_COMPARE. MPI.IDENT results if the comm1 and comm2 are references to the same object (ie, if comm1 == comm2). MPI.CONGRUENT results if the underlying groups are identical but the communicators differ by context. MPI.SIMILAR results if the underlying groups are similar but the communicators differ by context. MPI.UNEQUAL results otherwise.

Object Comm.clone()

returns:

copy of this communicator

Duplicate this communicator. Java binding of the MPI operation MPI_COMM_DUP. The new communicator is ``congruent'' to the old one, but has a different context.

• Rationale. The decision to use the standard Java clone method means the static result type must be Object. The dynamic type will be that of the Comm subclass of the parent. MPI-defined and user-defined subclasses of Comm will generally override clone to ensure all relevant attributes are copied.(End of rationale.)

Intracomm Intracomm.Create(Group group)

group	group which is a subset of the group of this communicator
returns:	new communicator

Create a new communicator. Java binding of the MPI operation MPI_COMM_CREATE.

Intracomm Intracomm.Split(int color, int key)

color	control of subset assignment
key	control of rank assignment
returns:	new communicator

Partition the group associated with this communicator and create a new communicator within each subgroup. Java binding of the MPI operation MPI_COMM_SPLIT.

void Comm.Free()

Destroy this communicator. Java binding of the MPI operation MPI_COMM_FREE.

• Rationale. An explicitly called Free method is required rather than an implicitly called finalize method, because MPI_COMM_FREE is a collective operation. We cannot assume that the Java garbage collector will call a finalize method synchronously on all processors.(End of rationale.)

boolean Comm.Is_null()

returns:

true if the communicator object has been freed, false otherwise

Replaces comparision with MPI_COMM_NULL.