Concurrent Access of Priority Queues

The heap is an important data structure used as a priority queue in a wide variety of parallel algorithms (e.g., multiprocessor scheduling, branch-and-bound). In these algorithms, contention for the shared heap limits the obtainable speedup. This paper presents an approach to allow concurrent insertions and deletions on the heap in a shared-memory multiprocessor. The scheme also retains the strict priority ordering of the serial-access heap algorithms; i.e., a delete operation returns the best key of all keys that have been inserted or are being inserted at the time delete is started. Our experimental results on the BBN Butterfly parallel processor demonstrate that the use of the concurrentheap algorithms in parallel branch-and-bound improves its performance substantially.