BDDT:: block-level dynamic dependence analysisfor deterministic task-based parallelism

Reasoning about synchronization, ordering and conflicting memory accesses makes parallel programming difficult, error-prone and hard to test, debug and maintain. Task-parallel programming models such as OpenMP, Cilk and Sequoia offer a more structured way of expressing parallelism than threads, but still require the programmer to manually find and enforce any ordering or memory dependencies among tasks. Programming models with implicit parallelism such as SvS, OoOJava, or StarSs lift this limitation by automatically inferring parallelism and dependencies, requiring the programmer to describe the memory footprint of each task. Current limitations of these systems require the programmer to restrict task footprints into either whole and isolated program objects, one-dimensional array ranges, or static compile-time regions; all producing over-approximations and false dependencies that reduce the available parallelism in the program. This paper presents BDDT, a task-parallel runtime system that dynamically discovers and resolves dependencies among parallel tasks. BDDT allows the programmer to specify detailed task footprints on any memory address range or multidimensional array tile. BDDT uses a block-based dependence analysis with arbitrary granularity, making it easier to apply to