Maximum Likelihood Estimation and Other Probabilistic Algorithms

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CCR-9820885Kannan, S.This project pursues research in a number of areas with the common theme being the design and analysis of probabilistic algorithms.Maximum Likelihood Estimation is a classical and important technique in statistics. Specific versions of this general problem are defined by considering specific stochastic processes that generate the sample data. This problem has generally been thought to be computationally intractable for most interesting applications. However, this project seeks to create very efficient algorithms that find approximately the most likely solutions. Specifically such algorithms are sought for important problems in computational biology such as phylogeny construction and multiple alignment. The project also investigates similar approaches for the problem of inferring Belief Nets, a popular stochastic model in artificial intelligence.The problem of contention is concerned with message transmission over an ethernet where messages arrive according to a stochastic process such as a Poisson process. Each message uses a protocol whereby it attempts to transmit itself at each time instant with some probability.A central open question is whether there is a protocol that ensures that the system is "stable." The PI proved that the answer is "no" for a number of "natural" classes of protocols and is working on extending these proofs to all acknowledgement-based protocols. Finally, the project investigate new models and problems in the area of program checking which again involves the design of randomized algorithms.