MPI Programming Guide

Chapter 4. Programming considerations for user applications in POE

This chapter describes various limitations, restrictions, and programming considerations for user applications written to run under the IBM Parallel Environment for AIX (PE) licensed program.

PE includes two versions of the message-passing libraries: the signal-handling library and the threads library.

• The signal-handling library uses AIX signals as an asynchronous way to move data in and out of message buffers. These signals also ensure that message packets are acknowledged and retransmitted when necessary. The signal-handling library supports both MPI and MPL calls, but only MPI-1 functionality.
• The threads library uses AIX kernel threads for the same message-passing tasks. It supports MPI only. The threads library also supports message passing on user-created threads, and includes support for both 32-bit and 64-bit applications.

  The threads library is required if MPI coexists with the other user space protocols, such as the low-level communication API (LAPI) on the IBM RS/6000 SP. LAPI programs cannot be run on clusters made up of IBM pSeries systems, IBM RS/6000 systems, or both. LAPI only supports the SP Switch or the SP Switch2.

This chapter consists of sections about the programming considerations common to both libraries, as well as those unique to either the signal-handling library or the threads library:

• The signal-handling library and the threads library: considerations
• The signal-handling library: considerations
• The threads library: considerations