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MPI Issues

AUTOPACK creates its own MPI communicator and will not interfere with any normal MPI operations. The user may mix and match calls to either library as appropriate.

At present, all messages are sent and received using type MPI_BYTE. No data conversion is done between sender and receiver.

The library reserves use of several message tags at the top of the permissible range of tag numbers. The maximum MPI tag is set by the AP_MAX_TAG (default 32767). The user code must use message tags that are less than AP_LIB_TAG (default 32764). These constants are defined in the source file ``header.h''.

The library requires the message tag to be declared at the time of message buffer allocation. The library does not actually need to know the tag until the message is sent, but for simplicity the API asks for all the information up front.

At present, all receives are performed via MPI_Probe()/MPI_Iprobe() and MPI_Recv(). While this is a correct use of MPI, some MPI implementations may not operate as efficiently as they could compared to using MPI_Irecv(). Implementing the library functionality using MPI_Irecv() is planned although its use will impose some restrictions.


next up previous contents
Next: Acknowledgments Up: AUTOPACK User Manual 1 Previous: Deterministic Message Delivery   Contents
Raymond Loy 2000-05-12