We address the parallelization and distributed execution of an algorithm from the area of symbolic computation: propositional satisfiability (SAT) checking with dynamic learning. Our parallel programming models are strict multithreading for the core SAT checking procedure, complemented by mobile agents realizing a distributed dynamic learning process. Individual threads treat dynamically created subproblems, while mobile agents collect and distribute pertinent knowledge obtained during the learning process. The parallel algorithm runs on top of our parallel system platform DOTS (Distributed Object-Oriented Threads System), which provides support for our parallel programming models in highly heterogeneous distributed systems. We present performance measurements evaluating the performance gains by our approach in different application domains with practical significance. Key words: parallel symbolic computation, parallel propositional satisfiability checking, distributed multithreading 1

We describe the Distributed Object-Oriented Threads System (DOTS), a programming environment designed to support object-oriented fork/join parallel programming in a heterogeneous distributed environment. A mixed network of Windows NT PC’s and UNIX workstations is transformed by DOTS into a homogeneous pool of anonymous compute servers forming together a multicomputer. DOTS is a complete redesign of the Distributed Threads System (DTS) using the object-oriented paradigm both in its internal implementation and in the programming paradigm it supports. It has been used for the parallelization of applications in the field of computer algebra and in the field of computer graphics. We also give a brief account of applications in the domain of symbolic computation that were developed using DTS. Key words: distributed threads system, heterogeneous networks, Windows NT

Abstract. We describe the design and implementation of the Distributed Object-Oriented Threads System (DOTS). This system is a complete redesign of the Distributed Threads System (DTS) using the object-oriented paradigm both in its internal implementation and in the programming paradigm it supports. DOTS extends the support for fork/join parallel programming from shared memory threads to a distributed environment. It is currently implemented on top of the Adaptive Communication Environment (ACE). A heterogeneous network of Windows NT PC’s and of UNIX workstations is transformed by DOTS into a homogeneous pool of anonymous compute servers. DOTS has been used recently in applications from computer graphics and computational number theory. We also discuss the performance characteristics of DOTS for a workstation cluster running under Solaris and a PC network using Windows NT, as they were obtained from a prototypical example. 1