An Efficient Task Clustering Heuristic for Scheduling DAGs on Multiprocessors

For task clustering with no duplication, the DSC algorithm of Gerasoulis and Yang is empirically the best known algorithm to date in terms of both speed and solution quality. The DSC algorithm is based on the critical path method. In this paper, we present an algorithm called CASS-II for task clustering with no duplication which is competitive to DSC in terms of both speed and solution quality. With respect to speed, CASS-II is better than DSC: it has a time complexity of O(jEj + jV j lg jV j), as opposed to DSC’s O((jEj + jV j) lg jV j). Indeed, our experimental results show that CASS-II is between 3 to 5 times faster than DSC. (It is worth pointing out that we used the C code for DSC developed by the authors of the DSC algorithm. The C code for CASS-II was developed by the authors of this paper.) With respect to solution quality, experimental results show that CASS-II is virtually as good as DSC and, in fact, even outperforms DSC for very fine grain DAGs (granularity less than 0.6).