Yonatan Aumann

Bar Ilan University, Gan, Tel Aviv, Israel

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Publications (87)17.13 Total impact

  • Amos Azaria, Yonatan Aumann, Sarit Kraus
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    ABSTRACT: Crowdsourcing applications frequently employ many individual workers, each performing a small amount of work. In such settings, individually determining the reward for each assignment and worker may seem economically beneficial, but is inapplicable if manually performed. We thus consider the problem of designing automated agents for automatic reward determination and negotiation in such settings. We formally describe this problem and show that it is NP-hard. We therefore present two automated agents for the problem, based on two different models of human behavior. The first, the Reservation Price Based Agent (RPBA), is based on the concept of a RP, and the second, the No Bargaining Agent (NBA) which tries to avoid any negotiation. The performance of the agents is tested in extensive experiments with real human subjects, where both NBA and RPBA outperform strategies developed by human experts.
    Autonomous Agents and Multi-Agent Systems 01/2013; · 0.79 Impact Factor
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    Yonatan Aumann, Yair Dombb, Avinatan Hassidim
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    ABSTRACT: We consider a setting in which a single divisible good ("cake") needs to be divided between n players, each with a possibly di?fferent valuation function over pieces of the cake. For this setting, we address the problem of ?finding divisions that maximize the social welfare, focusing on divisions where each player needs to get one contiguous piece of the cake. We show that for both the utilitarian and the egalitarian social welfare functions it is NP-hard to find the optimal division. For the utilitarian welfare, we provide a constant factor approximation algorithm, and prove that no FPTAS is possible unless P=NP. For egalitarian welfare, we prove that it is NP-hard to approximate the optimum to any factor smaller than 2. For the case where the number of players is small, we provide an FPT (fixed parameter tractable) FPTAS for both the utilitarian and the egalitarian welfare objectives.
    05/2012;
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    ABSTRACT: We introduce a generalization of interval graphs, which we call dotted interval graphs (DIG). A dotted interval graph is an intersection graph of arithmetic progressions (=dotted intervals). Coloring of dotted intervals graphs naturally arises in the context of high throughput genotyping. We study the properties of dotted interval graphs, with a focus on coloring. We show that any graph is a DIG but that DIG d graphs, i.e. DIGs in which the arithmetic progressions have a jump of at most d, form a strict hierarchy. We show that coloring DIG d graphs is NP-complete even for d = 2. For any fixed d, we provide a 7 8 d approximation for the coloring of DIG d graphs.
    ACM Transactions on Algorithms - TALG. 01/2012;
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    Orit Arzi, Yonatan Aumann, Yair Dombb
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    ABSTRACT: We consider the problem of fairly dividing a heterogeneous cake between a number of players with different tastes. In this setting, it is known that fairness requirements may result in a suboptimal division from the social welfare standpoint. Here, we show that in some cases, discarding some of the cake and fairly dividing only the remainder may be socially preferable to any fair division of the entire cake. We study this phenomenon, providing asymptotically-tight bounds on the social improvement achievable by such discarding.
    Computing Research Repository - CORR. 01/2011;
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    Orit Arzi, Yonatan Aumann, Yair Dombb
    Algorithmic Game Theory, 4th International Symposium, SAGT 2011, Amalfi, Italy, October 17-19, 2011. Proceedings; 01/2011
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    ACM Transactions on Algorithms. 01/2011; 7:24.
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    Tammar Shrot, Yonatan Aumann, Sarit Kraus
    9th International Conference on Autonomous Agents and Multiagent Systems (AAMAS 2010), Toronto, Canada, May 10-14, 2010, Volume 1-3; 01/2010
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    Yonatan Aumann, Yair Dombb
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    ABSTRACT: We consider the issue of fair division of goods, using the cake cutting abstraction, and aim to bound the possible degradation in social welfare due to the fairness requirements. Previous work has considered this problem for the setting where the division may allocate each player any number of unconnected pieces. Here, we consider the setting where each player must receive a single connected piece. For this setting, we provide tight bounds on the maximum possible degradation to both utilitarian and egalitarian welfare due to three fairness criteria — proportionality, envy-freeness and equitability.
    Internet and Network Economics - 6th International Workshop, WINE 2010, Stanford, CA, USA, December 13-17, 2010. Proceedings; 01/2010
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    Yonatan Aumann, Yair Dombb
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    ABSTRACT: We analyze the Pareto efficiency, or inefficiency, of solutions to routing games and load balancing games, focusing on Nash equilibria and greedy solutions to these games. For some settings, we show that the solutions are necessarily Pareto optimal. When this is not the case, we provide a measure to quantify the distance of the solution from Pareto efficiency. Using this measure, we provide upper and lower bounds on the “Pareto inefficiency” of the different solutions. The settings we consider include load balancing games on identical, uniformly-related, and unrelated machines, both using pure and mixed strategies, and nonatomic routing in general and some specific networks.
    Algorithmic Game Theory - Third International Symposium, SAGT 2010, Athens, Greece, October 18-20, 2010. Proceedings; 01/2010
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    J. Comput. Syst. Sci. 01/2009; 75:359-370.
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    ABSTRACT: Historically, approximate pattern matching has mainly focused at coping with errors in the data, while the order of the text/pattern was assumed to be more or less correct. In this paper we consider a class of pattern matching problems where the content is assumed to be correct, while the locations may have shifted/changed. We formally define a broad class of problems of this type, capturing situations in which the pattern is obtained from the text by a sequence of rearrangements. We consider several natural rearrangement schemes, including the analogues of the ℓ1 and ℓ2 distances, as well as two distances based on interchanges. For these, we present efficient algorithms to solve the resulting string matching problems.
    Journal of Computer and System Sciences. 01/2009;
  • Theor. Comput. Sci. 01/2009; 410:5334-5346.
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    Tammar Shrot, Yonatan Aumann, Sarit Kraus
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    ABSTRACT: Coalition formation is a key topic in multi-agent systems (mas). Coalitions enable agents to achieve goals that they may not have been able to achieve independently, and en- courages resource sharing among agents with different goals. A range of previous studies have found that problems in coalitional games tend to be computationally complex. However, such hardness results consider the entire input as one, ignoring any structural information on the instances. In the case of coalition formation problems, this bundles to- gether several distinct elements of the input, e.g. the agent set, the goal set, the resources, etc. In this paper we re- examine the complexity of coalition formation problems in the coalition resources game model, as a function of their distinct input elements, using the theory of parameterized complexity. The analysis shows that not all parts of the in- put are created equal, and that many instances of the prob- lem are actually tractable. We show that the problems are FPT in the number of goals, implying that if the number of goals is bounded then an efficient algorithm is available. Similarly, the problems are FPT in the combination of the number of agents and resources, again implying that if these parameters are bounded, then an efficient algorithm is avail- able. On the other hand, the problems are para- NP hard in the number of resources, implying that even if we bound the number of resources the problems (probably) remain hard. Additionally, we show that most problems are W(1)-hard in the size of the coalition of interest, indicating that there is (probably) no algorithm polynomial in all but the coalition size. The exact definitions of the parameterized complexity notions FPT, Para- NP and W(1) are provided herein.
    8th International Joint Conference on Autonomous Agents and Multiagent Systems (AAMAS 2009), Budapest, Hungary, May 10-15, 2009, Volume 1; 01/2009
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    ABSTRACT: Recently, a new pattern matching paradigm was proposed, pattern matching with address errors. In this paradigm approximate string matching problems are studied, where the content is unaltered and only the locations of the different entries may change. Specifically, a broad class of problems was defined-the class of rearrangement errors. In this type of error the pattern is transformed through a sequence of rearrangement operations, each with an associated cost. The natural @?"1 and @?"2 rearrangement systems were considered. The best algorithm presented for general patterns, that may have repeating symbols, is O(nm). In this paper, we show that the problem can be approximated in linear time for general patterns! Another natural rearrangement system is considered in this paper-the @?"~ rearrangement distance. For this new rearrangement system efficient exact solutions for different variants of the problem are provided, as well as a faster approximation.
    Theoretical Computer Science 01/2009; 410(43):4382-4390. · 0.49 Impact Factor
  • Theor. Comput. Sci. 01/2009; 410:4382-4390.
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    Noam Hazon, Yonatan Aumann, Sarit Kraus
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    ABSTRACT: This paper considers the setting wherein a group of agents (e.g., robots) is seeking to obtain a given tan- gible good, potentially available at different loca- tions in a physical environment. Traveling between locations, as well as acquiring the good at any given location consumes from the resources available to the agents (e.g., battery charge). The availability of the good at any given location, as well as the ex- act cost of acquiring the good at the location is not fully known in advance, and observed only upon physically arriving at the location. However, a- priori probabilities on the availability and poten- tial cost are provided. Given such as setting, the problem is to find a strategy/plan that maximizes the probability of acquiring the good while mini- mizing resource consumption. Sample applications include agents in exploration and patrol missions, e.g., rovers on Mars seeking to mine a specific min- eral. Although this model captures many real world scenarios, it has not been investigated so far. We focus on the case where locations are aligned along a path, and study several variants of the prob- lem, analyzing the effects of communication and coordination. For the case that agents can com- municate, we present a polynomial algorithm that works for any fixed number of agents. For non- communicating agents, we present a polynomial al- gorithm that is suitable for any number of agents. Finally, we analyze the difference between homo- geneous and heterogeneous agents, both with re- spect to their allotted resources and with respect to their capabilities.
    IJCAI 2009, Proceedings of the 21st International Joint Conference on Artificial Intelligence, Pasadena, California, USA, July 11-17, 2009; 01/2009
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    ABSTRACT: In this paper, the optimality proof of Lempel-Ziv coding is re-studied, and a much more general compression optimality theorem is derived. In particular, the property of quasi-distinct parsing is defined. This property is much weaker than distinct parsing required in the original proof, yet we show that the theorem holds with this weaker property as well. This provides a better understanding of the optimality proof of Lempel-Ziv coding, together with a new tool for proving optimality of other compression schemes. To demonstrate the possible use of this generalization, a new coding method – the APT coding – is presented. This new coding method is based on a principle that is very different from Lempel-Ziv’s coding. Moreover, it does not directly define any parsing technique. Nevertheless, APT coding is analyzed in this paper and using the generalized theorem shown to be asymptotically optimal up to a constant factor, if APT quasi-distinctness hypothesis holds. An empirical evidence that this hypothesis holds is also given.
    Combinatorial Pattern Matching, 20th Annual Symposium, CPM 2009, Lille, France, June 22-24, 2009, Proceedings; 01/2009
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    ABSTRACT: A string S ∈ Σ m can be viewed as a set of pairs S = { (σ i , i) : i ∈ { 0,..., m − 1} }. We consider approximate pattern matching problems arising from the setting where errors are introduced to the location component (i), rather than the more traditional setting, where errors are introduced to the content itself (σ i ). In this paper, we consider the case where bits of i may be erroneously flipped, either in a consistent or transient manner. We formally define the corresponding approximate pattern matching problems, and provide efficient algorithms for their resolution, while introducing some novel techniques.
    06/2008: pages 118-129;
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    ABSTRACT: We investigate the extent to which it is possible to evaluate the probability of a particular candidate winning an elec- tion, given imperfect information about the preferences of the electorate. We assume that for each voter, we have a probability distribution over a set of preference orderings. Thus, for each voter, we have a number of possible prefer- ence orderings { we do not know which of these orderings actually represents the voters' preferences, but we know for each one the probability that it does. We give a polynomial algorithm to solve the problem of computing the probability that a given candidate will win when the number of candi- dates is a constant. However, when the number of candi- dates is not bounded, we prove that the problem becomes #P-Hard for the Plurality, Borda, and Copeland voting pro- tocols. We further show that even evaluating if a candidate has any chance to win is NP-Complete for the Plurality vot- ing protocol, in the weighted voters case. We give a poly- nomial algorithm for this problem when the voters' weights are equal.
    7th International Joint Conference on Autonomous Agents and Multiagent Systems (AAMAS 2008), Estoril, Portugal, May 12-16, 2008, Volume 2; 01/2008
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    Yonatan Aumann, Noam Hazon, Sarit Kraus, David Sarne
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    ABSTRACT: This paper considers the problem of an agent searching for a resource or a tangible good in a physical environment, where at each stage of its search it observes one source where this good can be found. The cost of acquiring the resource or good at a given source is uncertain (a-priori), and the agent can observe its true value only when physically arriving at the source. Sample applications involving this type of search in- clude agents in exploration and patrol missions (e.g., an agent seeking to find the best location to deploy sensing equipment along its path). The uniqueness of these settings is that the expense of observing the source on each step of the process derives from the last source the agent explored. We ana- lyze three variants of the problem, differing in their objec- tive: minimizing the total expected cost, maximizing the suc- cess probability given an initial budget, and minimizing the budget necessary to obtain a given success probability. For each variant, we first introduce and analyze the problem with a single agent, either providing a polynomial solution to the problem or proving it is NP-Complete. We also introduce an innovative fully polynomial time approximation scheme al- gorithm for the minimum budget variant. Finally, the results for the single agent case are generalized to multi-agent set- tings.
    Proceedings of the Twenty-Third AAAI Conference on Artificial Intelligence, AAAI 2008, Chicago, Illinois, USA, July 13-17, 2008; 01/2008

Publication Stats

937 Citations
17.13 Total Impact Points

Institutions

  • 1970–2013
    • Bar Ilan University
      • Department of Computer Science
      Gan, Tel Aviv, Israel
  • 2006–2007
    • Technion - Israel Institute of Technology
      H̱efa, Haifa District, Israel
  • 2003
    • CUNY Graduate Center
      New York City, New York, United States
  • 1992–1994
    • Hebrew University of Jerusalem
      Yerushalayim, Jerusalem District, Israel
  • 1993
    • Weizmann Institute of Science
      Israel