Pack and unpack

int Comm.pack(Object inbuf, int offset, int incount,
              Datatype datatype,
              byte [] outbuf, int position)

inbuf	input buffer array
offset	initial offset in input buffer
incount	number of items in input buffer
datatype	datatype of each item in input buffer
outbuf	output buffer
position	initial position in ouput buffer
returns:	final position in output buffer

Packs message in send buffer inbuf into space specified in outbuf. Java binding of the MPI operation MPI_PACK. The return value is the output value of position--the inital value incremented by the number of bytes written.

byte[] Comm.pack(Object inbuf, int offset, int incount,
                 Datatype datatype)

inbuf	input buffer array
offset	initial offset in input buffer
incount	number of items in input buffer
datatype	datatype of each item in input buffer
returns:	output buffer

Packs message in send buffer inbuf into buffer space allocated internally.

• Rationale. This variant of pack is essentially equivalent to calling MPI_PACK_SIZE to find the amount of space needed for a packed message, allocating a suitable byte vector, then calling the previous variant of pack. Unfortunately the object serialization mechanisms of Java do not provide a convenient way of precomputing the amount of space required to pack objects (there is no analogue to MPI_PACK_SIZE). So if the base type of the message is MPI.OBJECT the second form of pack is more convenient.(End of rationale.)

int Comm.unpack(byte [] inbuf, int position,
                Object outbuf, int offset, int outcount,
                Datatype datatype)

inbuf	input buffer
position	initial position in input buffer
outbuf	output buffer array
offset	initial offset in output buffer
outcount	number of items in output buffer
datatype	datatype of each item in output buffer
returns:	final position in input buffer

Unpacks message in receive buffer outbuf into space specified in inbuf. Java binding of the MPI operation MPI_UNPACK. The return value is the output value of position--the inital value incremented by the number of bytes read.

int Comm.packSize(int incount, Datatype datatype)

incount	number of items in input buffer
datatype	datatype of each item in input buffer
returns:	upper bound on size of packed message

Returns an upper bound on the increment of position effected by pack. Java binding of the MPI operation MPI_PACK_SIZE. It is an error to call this function if the base type of datatype is MPI.OBJECT.