Vibhor Bhatt

Microsoft

Mutual Exclusion is a fundamental problem in distributed computing, and the problem of proving upper and lower bounds on the RMR complexity of this problem has been extensively studied. Here, we give matching lower and upper bounds on how RMR complexity trades off with space. Two implications of our results are that constant RMR complexity is impos...

Brandenburg and Anderson [1,2] recently introduced a phase-fair readers/writers lock [1,2], where read and write phases alternate: when the writer leaves the CS, any waiting reader will enter the CS before the next writer enters the CS; similarly, if a reader is in the CS and a writer is waiting, any new reader that now enters the Try section will...

We present an algorithm to solve the GROUP MUTUAL EXCLUSION problem in the cache-coherent (CC) model. For the same prob-lem in the distributed shared memory (DSM) model, Danek and Hadzilacos presented algorithms of O(n) remote memory refer-ences (RMR) and proved a matching lower bound, where n is the number of processes. We show that in the CC mode...

We study Reader-Writer Exclusion [1], a well-known variant of the Mutual Exclusion problem [2] where processes are divided into two classes - readers and writers - and multiple readers can be in the Critical Section (CS) at the same time, although no process may be in the CS at the same time as a writer. Since readers don't conflict with each other...

Research over the past two decades has identified the weakest failure detectors for several important problems in fault-tolerant distributed computing. A recent work has shown that, for a certain definition of the term “problem,” every problem that is solvable using failure detectors has a weakest failure detector. In sharp contrast to these result...

It is well known that the failure detector Ω is necessary and sufficient to solve consensus in asynchronous message passing systems where a majority of processes is guaranteed to be correct [1,2]. But what if the problem were to be solved in an arbitrary environment where any number of processes may fail and at any times? The answer was provided by...

Traditional genetic algorithms with elitist selection are unable to locate more than one solution in a multimodal fitness landscape in a single run. This genetic drift is illustrated in Mapex, a smart spatial analysis technique, employing a genetic algorithm for spatial cluster discovery. However, for detecting multiple clusters Mapex provides a no...

The computationally NP-hard timetabling problem has been solved manually for a long time. The problem's complexity has thwarted attempts to use computer based deterministic methods, to solve it. More successful approaches have used genetic algorithms, because they are robust enough in such a huge problem space. In this paper we present new and effi...

Mutual exclusion is not solvable in an asynchronous message-passing system where pro- cesses are subject to crash failures. Delporte-Gallet et. a l. determined the weakest failure detector to solve this problem when a majority of processes are correct. Here we identify the weakest failure detector to solve mutual exclusion in any environment, i.e.,...