The STARTECH Massively-Parallel Chess Program

The StarTech massively parallel chess program, running on a 512-processor Connection Machine CM-5 supercomputer, tied for third place at the 1993 ACM International Computer Chess Championship. StarTech employs the Jamboree search algorithm, a natural extension of J. Pearl’s Scout search algorithm, to find parallelism in game-tree searches. StarTech’s work-stealing scheduler distributes the work specified by the search algorithm across the processors of the CM-5. StarTech uses a global transposition table shared among the processors. StarTech has an informally estimated rating of over 2400 USCF. Two performance measures help in understanding the performance of the StarTech program: the work, W , and the critical path length,C. The Jamboree search algorithm used in StarTech seems to perform about 2 to 3 times more work than does our best serial implementation. The critical path length, under tournament conditions, is less than 0.1% of the total work, yielding an average parallelism of over 1000. The StarTech scheduler achieves actual performance of approximatelyT 1:02W=P + 1:5C on P processors. The critical path and work can be used to tune performance by allowing development of the program on a small, readily accessable, machine while predicting the performance on a big, tournament-sized, machine.