Title: Allocation Problems with Partial Information

Pushkar Tripathi
Algorithms, Combinatorics, and Optimization College of Computing Georgia Institute of Technology

Date: Friday, May 25th, 2012
Time: 3:30 pm EDT
Location: Skiles 005

Committee:

• Dr. Vijay Vazirani (Advisor), School of Computer Science, Georgia Institute of Technology
• Dr. Ozlem Ergun (Reader), School of Industrial and Systems Engineering, Georgia Institute of Technology
• Dr. Nina Balcan, School of Computer Science, Georgia Institute of Technology
• Dr. Shabbir Ahmed, School of Industrial and Systems Engineering, Georgia Institute of Technology
• Dr. Prasad Tetali, School of Mathematics and School of Computer Science, Georgia Institute of Technology

Abstract:
Allocation problems have been central to the development of the theory of algorithms and also find applications in several realms of computer science and economics. In this thesis we initiate a systematic study of these problems in situations with limited information.

Towards this end we explore several modes by which data may be obfuscated from the algorithm. We begin by investigating temporal constraints where data is revealed to the algorithm over time. Concretely, we consider the online bipartite matching problem in the unknown distribution model and present the first algorithm that breaches the 1-1/e barrier for this problem.

Next we study issues arising from data acquisition costs that are prevalent in ad-systems and kidney exchanges. Motivated by these constraints we introduce the query-commit model and present a 0.56 factor randomized algorithm for the maximum matching problem in this model. Our algorithm is a variant of the greedy algorithm and uses correlated randomness to attain a factor better than 0.5. We also study the maximum matching, and the adwords problem in a stochastic variant of this model and present constant factor algorithms.

Finally, we assess the approximability of several classical allocation problems with multiple agents having complex non-linear cost functions. This presents an additional obstacle since the support for the cost functions may be extremely large entailing oracle access. We show tight information theoretic lower bounds for the general class of submodular functions and also extend these results to get lower bounds for a subclass of succinctly representable non-linear cost functions.