Distributed Computing

Volume 3724 of the series Lecture Notes in Computer Science pp 108-121

Non-blocking Hashtables with Open Addressing

  • Chris PurcellAffiliated withComputer Laboratory, University of Cambridge
  • , Tim HarrisAffiliated withMicrosoft Research Ltd.

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We present the first non-blocking hashtable based on open addressing that provides the following benefits: it combines good cache locality, accessing a single cacheline if there are no collisions, with short straight-line code; it needs no storage overhead for pointers and memory allocator schemes, having instead an overhead of two words per bucket; it does not need to periodically reorganise or replicate the table; and it does not need garbage collection, even with arbitrary-sized keys. Open problems include resizing the table and replacing, rather than erasing, entries. The result is a highly-concurrent set algorithm that approaches or outperforms the best externally-chained implementations we tested, with fixed memory costs and no need to select or fine-tune a garbage collector or locking strategy.