Portable Instrumented Communication Library (PICL)


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PICL is a subroutine library that implements a generic message-passing interface on a variety of multiprocessors. Programs written using PICL routines instead of the native commands for interprocessor communication are portable in the sense that they can be run on any machine on which the library has been implemented. Correct execution is also a function of the parameter values passed to the routines, but standard error trapping is used to inform the user when a parameter value is not legal on a particular machine. Programs written using PICL routines will also produce timestamped trace data on interprocessor communication, processor busy/idle times and simple user-defined events if a few additional statements are added to the source code. A separate facility called ParaGraph can be used to graphically view the trace data.

PICL differs from other outwardly similar systems in that it is a compatibility library with an integrated intrumentation package, and because it is intended to be a research tool. PICL supports the writing of portable programs without enforcing it. Machine-specific commands or functionality can still be invoked when necessary to get good performance. Portable instrumentation logic that is integrated with the message passing interface is also a unique feature, one that has proven to be extremely useful. Understanding the performance of a parallel code often requires the collection of both system and user-defined event data. Finally, to be a research tool requires that the code be easy to maintain, easy to extend, and easy to port to new platforms. Every effort has been made to keep PICL simple, and to make it available to other research groups who might be interested in porting it to their multiprocessors.

PICL 2.1 was authored by P. H. Worley at Oak Ridge National Laboratory. It is based on PICL 1.0, authored by G. A. Geist, M. T. Heath, B. W. Peyton, and P. H. Worley, and remains backward compatible with earlier versions of the library. The most recent version of the library can be obtained from the PICL web page. Questions and comments may be addressed to worleyph@ornl.gov.