Barrier Elimination Based on Access Dependency Analysis for OpenMP

In this paper, we propose a new compiler technique for eliminating barrier synchronizations. In our approach, the compiler collects access information about array accesses and analyzes data dependency. If there was no dependency, barrier synchronizations can be eliminated. Additionally, even if the dependency was detected, there are cases when the barrier synchronization can be replaced with send-receive pairs of communications. For evaluation, we executed two application programs: Jacobi Method and Gaussian Elimination, on a PC cluster with barrier elimination applied. For comparison, we also executed the programs before elimination of barrier synchronizations. With barrier elimination, 1) the execution time is always reduced, and 2) as the number of processors increases, the reduction ratio of the execution time also increases. For 16 processors, we obtained 19.00% and 50.36% of the reduction ratio for Jacobi Method and Gaussian Elimination respectively.