On Collision-fast Atomic Broadcast

Atomic Broadcast, an important abstraction in dependable distributed computing, is usually implemented by many instances of the well-known consensus problem. Some asynchronous consensus algorithms achieve the optimal latency of two (message) steps but cannot guarantee this latency even in good runs, with quick message delivery and no crashes. This is due to collisions, a result of concurrent proposals. Collision-fast consensus algorithms, which decide within two steps in good runs, exist under certain conditions. Their direct application to solving atomic broadcast, though, does not guarantee delivery in two steps for all messages unless a single failure is tolerated. We show a simple way to build a fault-tolerant collision-fast Atomic Broadcast algorithm based on a variation of the consensus problem we call M-Consensus. Our solution to M-Consensus extends the Paxos protocol to allow multiple processes, instead of the single leader, to have their proposals learned in two steps

HT-Paxos: High Throughput State-Machine Replication Protocol for Large Clustered Data Centers

Paxos is a prominent theory of state machine replication. Recent data intensive Systems those implement state machine replication generally require high throughput. Earlier versions of Paxos as few of them are classical Paxos, fast Paxos and generalized Paxos have a major focus on fault tolerance and latency but lacking in terms of throughput and scalability. A major reason for this is the heavyweight leader. Through offloading the leader, we can further increase throughput of the system. Ring Paxos, Multi Ring Paxos and S-Paxos are few prominent attempts in this direction for clustered data centers. In this paper, we are proposing HT-Paxos, a variant of Paxos that one is the best suitable for any large clustered data center. HT-Paxos further offloads the leader very significantly and hence increases the throughput and scalability of the system. While at the same time, among high throughput state-machine replication protocols, HT-Paxos provides reasonably low latency and response time

Game theoretic controller synthesis for multi-robot motion planning Part I : Trajectory based algorithms

We consider a class of multi-robot motion planning problems where each robot is associated with multiple objectives and decoupled task specifications. The problems are formulated as an open-loop non-cooperative differential game. A distributed anytime algorithm is proposed to compute a Nash equilibrium of the game. The following properties are proven: (i) the algorithm asymptotically converges to the set of Nash equilibrium; (ii) for scalar cost functionals, the price of stability equals one; (iii) for the worst case, the computational complexity and communication cost are linear in the robot number