Optimal Resilience in Systems That Mix Shared Memory and Message Passing

We investigate the minimal number of failures that can partition a system where processes communicate both through shared memory and by message passing. We prove that this number precisely captures the resilience that can be achieved by algorithms that implement a variety of shared objects, like registers and atomic snapshots, and solve common tasks, like randomized consensus, approximate agreement and renaming. This has implications for the m&m-model of [Aguilera et al., 2018] and for the hybrid, cluster-based model of [Damien Imbs and Michel Raynal, 2013; Michel Raynal and Jiannong Cao, 2019]

Optimal Register Construction in M&M Systems

Motivated by recent distributed systems technology, Aguilera et al. introduced a hybrid model of distributed computing, called message-and-memory model or m&m model for short [Marcos K. Aguilera et al., 2018]. In this model, processes can communicate by message passing and also by accessing some shared memory. We consider the basic problem of implementing an atomic single-writer multi-reader (SWMR) register shared by all the processes in m&m systems. Specifically, we give an algorithm that implements such a register in m&m systems and show that it is optimal in the number of process crashes that it can tolerate. This generalizes the well-known implementation of an atomic SWMR register in a pure message-passing system [Attiya et al., 1995]