Analysis of Concurrent Lock-Free Hash Tries with Constant-Time Operations

Aleksandar Prokopec


Ctrie is a scalable concurrent non-blocking dictionary data structure, with good cache locality, and non-blocking linearizable iterators.

However, operations on most existing concurrent hash tries run in O(log n) time. In this technical report, we extend the standard concurrent hash-tries with an auxiliary data structure called a cache. The cache is essentially an array that stores pointers to a specific level of the hash trie. We analyze the performance implications of adding a cache, and prove that the running time of the basic operations becomes O(1).

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[1] W.G. Cochran. 1977. Sampling Techniques. Wiley.

[2] Aleksandar Prokopec. 2018. Cache-Tries: Concurrent Lock-Free Hash Tries with Constant Time Operations. (2018)

[3] Aleksandar Prokopec, Phil Bagwell, and Martin Odersky. 2011. Lock-Free Resizeable Concurrent Tries. Springer Berlin Heidelberg, Berlin, Heidelberg, 156–170.

[4] Aleksandar Prokopec, Nathan Grasso Bronson, Phil Bagwell, and Martin Odersky. 2012. Concurrent Tries with Efficient Non-blocking Snapshots. (2012), 151–160.