About me

I am a Ph.D. candidate at the Department of Computer Science of Cornell University. My advisor is Prof. Bart Selman. I got my Diploma (5 year degree) in Electrical and Computer Engineering, with focus on Computer Engineering and Sciences at the National Technical Univ. of Athens, Greece.

Research interests

My current research focuses on computing strategies for complex games that involve participating in several auctions with various different rules each, when it is not possible to find an “optimal” strategy, e.g equilibrium strategy. I’m involved in the Trading Agent Competition, and my entry agent WhiteBear is probably the most consistently high-scoring agent in the TAC Classic game. I’m also interested in other auction related problems and strategies that agents can use to maximize their profit.

Publications

1.      Using Equilibria to Handle Design Tradeoffs of Autonomous Trading Agents [pdf]
Ioannis A. Vetsikas and Bart Selman
Draft (not published yet)
This paper is an extension of [2]. It provides several novel Bayes Nash equilibria and it describes the complete system of differential equations that needs to be solved in order to compute the Bayes Nash equilibria for the case of an m-th price auction that has several (8 in the case of TAC) closing times; we discover several equilibria (depending on the assumptions made by the agent). The experimental section extends the methodology in [5]; this section is not completed in this draft.

2.      Bayes Nash Equilibria for m-th Price Auctions with Multiple Closing times [pdf]
Ioannis A. Vetsikas and Bart Selman
ACM Exchanges, 2005 (to appear)
This paper presents some novel Bayes Nash equilibria that we computed for the case of an m-th price auction that has at least 2 possible closing times.

3.      Autonomous Trading Agent Design in the Presence of Tradeoffs [pdf]
Ioannis A. Vetsikas and Bart Selman
7th International Conference on Electronic Commerce, Xian, China, 2005
In this paper we present several issues and improvements that were not presented in [5]. We also present a complete set of experiments for both versions of the TAC game (2001-2003 and post 2004) and describe the changes necessary to the 2004 agent.

4.      A Methodology and Equilibria for Design Tradeoffs of Autonomous Trading Agents [pdf]
Ioannis A. Vetsikas and Bart Selman
3rd International Conference on Autonomous Agents and Multiagent Systems (AAMAS-04), New York, USA, 2004 (poster)
In this paper we clarify and extend the methodology presented in [4]. One of the main differences is the introduction of strategies based on Bayes Nash equilibria. This paper was eventually split (with a lot of additions) into papers [1], [2] and [3].

5.      A Principled Study of the Design Tradeoffs for Autonomous Trading Agents [pdf]
Ioannis A. Vetsikas and Bart Selman
2nd International Conference on Autonomous Agents and Multiagent Systems (AAMAS-03), Melbourne, Australia, 2003
In this paper we present a methodology (mostly experimental) for determining the “optimal” strategy in any scenario where an agent needs to get several goods from several different auctions. There is some mention of our 2002 TAC entry.

6.      Design Tradeoffs for Autonomous Trading Agents [pdf]
Ioannis A. Vetsikas and Bart Selman
Eighth International Conference on Principles and Practice of Constraint Programming, Ithaca, NY, 2002 (doctoral section)
This paper is complementary to [7] and focuses a bit more on the optimization problem that our 2001 agent faced.

7.      WhiteBear: An Empirical Study of Design Tradeoffs for Autonomous Trading Agents [pdf]
Ioannis A. Vetsikas and Bart Selman
AAAI Workshop on Game Theoretic and Decision Theoretic Agents, Edmonton, Canada, 2002
This paper mainly examines the problem of the TAC 2001 game and our entry into the TAC 2001 competition.

8.      Structure and Phase Transition Phenomena in the VTC Problem [ps]
Ramon Bejar, Ioannis A. Vetsikas, Carla P. Gomes, Henry Kautz and Bart Selman
TASK-PI Darpa Workshop, Santa Fe, New Mexico, USA, April 2001
We examine computational issues involved in the computation of a “fair” allocation of chores to several contracted agents.

Software

I authored several versions of WhiteBear, the Cornell entry into the TAC competition.

·        TAC Classic in 2001, 2002, 2003, 2004 and 2005

·        TAC SCM in 2003 and 2004

Contact Info

Department of Computer Science
338 Upson Hall
Cornell University
Ithaca, NY 14853
Tel (office): 1-607-255-7987
Email : vetsikas@cs.cornell.edu