Portable Runtime Support for Asynchronous Simulation

           Chih-Po Wen and Katherine Yelick
       Computer Science Division, U.C. Berkeley


We present library and runtime support for portable asynchronous
applications, using event-driven simulation as an example.  Although
event-driven simulation has a natural source of parallelism between
the logical processes, real speedups have been hard to obtain because
of the fine-grained, unpredictable communication patterns.  Language
and systems software support is also lacking for asynchronous
problems.  Our runtime supports makes the applications portable, eases
performance tuning, and allows code re-use between applications.  Our
goal is to support a range of platforms with varying performance
characteristics, from tightly-coupled multiprocessors through networks
of workstations.  We discuss the performance issues in the runtime
support, describe a distributed event graph data structure, and
present performance numbers from a parallelized timing simulator
called SWEC.