Redistribution aware two-step scheduling for mixed-parallel applications

Applications raising in many scientific fields exhibit both data and task parallelism that have to be exploited efficiently. A classic approach is to structure those applications by a task graph whose nodes represent parallel computations. Scheduling such mixed-parallel applications is challenging even on a single homogeneous platform, such as a cluster. Most of the mixed-parallel application scheduling algorithms rely on two decoupled steps: allocation and mapping. This separation can induce unnecessary or costly data redistributions that have an impact on the overall performance. This is particularly true for data intensive applications. In this paper, we propose an original approach in which the allocations determined in the first step can be adapted during the second step in order to minimize the impact of these data redistributions. Two redistribution aware mapping strategies are detailed and a study of their impact on the schedule length is proposed through a comparison with an efficient two step algorithm over a broad range of experimental scenarios.