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Brief Announcement: Efficient Recoverable Writable-CAS

Prasad Jayanti
Sucharita Jayanti
Submitting to Principles of Distributed Computing (PODC) (2023)


We present DuraCAS, a durable, i.e., recoverably linearizable and detectable implementation of the CAS (compare-and-swap) primitive. DuraCAS is writable, meaning it supports a Write() operation along with CAS() and Read(); has constant time complexity per operation; allows for dynamic joining, meaning newly created processes (a.k.a. threads) of arbitrary names can join the protocol and access our implementation; and has adaptive space complexity, meaning the space use scales in the number of processes n that actually use the objects, as opposed to previous protocols whose space complexity depends on N, the maximum number of processes that the protocol is designed for. Furthermore, DuraCAS, requires only O(m + n) space to support m objects that get accessed by n processes, improving on the state-of-the-art O(m + N2). To our knowledge, DuraCAS is the first durable CAS algorithm that allows for dynamic joining, and is the first to exhibit adaptive space complexity.