异步共识的随机化协议

Randomized Consensus with Regular Registers

The well-known randomized consensus algorithm by Aspnes and Herlihy for asynchronous shared-memory systems was proved to work, even against a strong adversary, under the assumption that the registers that it uses are atomic registers. With atomic registers, every read or write operation is instantaneous (and thus indivisible). As pointed out by Golab et al. (2011), however, a randomized algorithm that works with atomic registers does not necessarily work if we replace the atomic registers that it uses with linearizable implementations of registers. This raises the following question: does the …

Que Sera Consensus: Simple Asynchronous Agreement with Private Coins and Threshold Logical Clocks

It is commonly held that asynchronous consensus is much more complex, difficult, and costly than partially-synchronous algorithms, especially without using common coins. This paper challenges that conventional wisdom with que sera consensus QSC, an approach to consensus that cleanly decomposes the agreement problem from that of network asynchrony. QSC uses only private coins and reaches consensus in $O(1)$ expected communication rounds. It relies on "lock-step" synchronous broadcast, but can run atop a threshold logical clock (TLC) algorithm to time and pace partially-reliable communication at…

On Atomic Registers and Randomized Consensus 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 [1]. In this model, processes can communicate by message passing and also by accessing some shared memory (e.g., through some RDMA connections). We first 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 proc…

Rapid Asynchronous Plurality Consensus

We consider distributed plurality consensus in a complete graph of size $n$ with $k$ initial opinions. We design an efficient and simple protocol in the asynchronous communication model that ensures that all nodes eventually agree on the initially most frequent opinion. In this model, each node is equipped with a random Poisson clock with parameter $λ=1$. Whenever a node's clock ticks, it samples some neighbors, uniformly at random and with replacement, and adjusts its opinion according to the sample. A prominent example is the so-called two-choices algorithm in the synchronous model, where in…

Triadic Consensus：一种群体投票的随机算法

Triadic Consensus: A Randomized Algorithm for Voting in a Crowd

典型的投票规则在有许多候选人的情况下不起作用。如果只有几百个候选人，那么即使是一个简单的任务，如选择一个最好的候选人变得不切实际。出于在互联网上发展群体共识机制的希望，候选人的数量可以很容易地数以千计，我们研究了一个基于瓮的投票规则，每个参与者作为选民和候选人。我们证明，当参与者躺在一个一维的空间，这个投票协议发现一个$(1-ε/sqrt{n})$近似的孔多塞赢家具有很高的概率，而只需要一个预期的$O(\frac{1}{ε^2}\log^2 \frac{n}{ε^2})$平均每个选民的比较。此外，该投票协议被证明有一个准真实的纳什均衡：即，一个纳什均衡存在，这可能不是真实的，但产生一个赢家具有相同的概率分布的真实的策略。