Kamal Jain

eBay Research Labs

We present prior robust algorithms for a large class of resource allocation problems where requests arrive one-by-one (online), drawn independently from an unknown distribution at every step. We design a single algorithm that, for every possible underlying distribution, obtains a $1-\epsilon$ fraction of the profit obtained by an algorithm that kno...

We present prior robust algorithms for a large class of resource allocation problems where requests arrive one-by-one (online), drawn independently from an unknown distribution at every step. We design a single algorithm that, for every possible underlying distribution, obtains a 1−ϵ fraction of the profit obtained by an algorithm that knows the en...

We present an exact characterization of utilities in competitive equilibria of two-sided matching markets in which the utility of each agent depends on the choice of partner and the terms of the partnership, potentially including monetary transfer. Examples of such markets include sellers and buyers or jobs and workers. Demange and Gale showed that...

We investigate the influence of different algorithmic choices on the approximation ratio in selfish scheduling. Our goal is to design local policies that minimize the inefficiency of resulting equilibria. In particular, we design optimal coordination mechanisms for unrelated machine scheduling, and improve the known approximation ratio from O(m) to...

Various embodiments provide offline algorithms for resource allocation. A known set of “offline” requests may be matched to available resources using an online resource allocation algorithm that models the offline resource allocation problem as though the requests were received stochastically. Requests may be scaled and then sampled to provide rand...

The first-price auction is popular in practice for its simplicity and transparency. Moreover, its potential virtues grow in complex settings where incentive compatible auctions may generate little or no revenue. Unfortunately, the first-price auction is poorly understood in theory because equilibrium is not a priori a credible predictor of bidder b...

We give a simple proof that the RANKING algorithm of Karp, Vazirani and Vazirani [KVV90] is 1-1/e competitive for the online bipartite matching problem. The proof is via a randomized primal-dual argument. Primal-dual algorithms have been successfully used for many online algorithm problems, but the dual constraints are always satisfied deterministi...

We study the optimal mechanism design problem faced by a market intermediary who makes revenue by connecting buyers and sellers. We first show that the optimal intermediation protocol has substantial structure: it is the solution to an algorithmic pricing problem in which seller's costs are replaced with virtual costs, and the sellers' payments nee...

A single advertisement often benefits many parties, for example, an ad for a Samsung laptop benefits Microsoft. We study this phenomenon in search advertising auctions and show that standard solutions, including the status quo ignorance of mutual benefit and a benefit-aware Vickrey-Clarke-Groves mechanism, perform poorly. In contrast, we show that...

Despite the pervasiveness of markets in our lives, little is known about the role of user interfaces (UIs) in promoting good decisions in market domains. How does the way we display market information to end users, and the set of choices we offer, influence users' decisions? In this paper, we introduce a new research agenda on "market user interfac...

We consider a significant generalization of the Adwords problem by allowing arbitrary concave returns, and we characterize the optimal competitive ratio achievable. The problem considers a sequence of items arriving online that have to be allocated to agents, with different agents bidding different amounts. The objective function is the sum, over e...

Two sided matching markets are among the most studied models in market design. There is a vast literature on the structure of competitive equilibria in these markets, yet most of it is focused on quasilinear settings. General (non-quasilinear) utilities can, for instance, model smooth budget constraints as a special case. Due to the difficulty of d...

We study bargaining networks, discussed in a recent paper of Kleinberg and Tardos [KT08], from the perspective of cooperative game theory. In particular we examine three solution concepts, the nucleolus, the core center and the core median. All solution concepts define unique solutions, so they provide testable predictions. We define a new monotoni...

We propose a generative model for social networks, both undirected and directed, that takes into account two fundamental characteristics of the user: background (specifically, the real world groups to which the user belongs); and behavior (namely, the ways in which the user engages in surfing activity and occasionally adds links to other users enco...

We present algorithms for a class of resource allocation problems both in the online setting with stochastic input and in the offline setting. This class of problems contains many interesting special cases such as the Adwords problem. In the online setting we introduce a new distributional model called the adversarial stochastic input model, which...

An auctioneer sells a single unit to a group of bidders using a second price auction. A subset of these bidders possess a coupon entitling them to a discount ofi the winning bid in the event they win the auction. Bidders without the coupon are at a disadvantage relative to the situation when nobody has any coupons. Therefore, in a loose sense, thes...

Online auctions in which items are sold in an online fashion with little knowledge about future bids are common in the internet environment. We study here a problem in which an auctioneer would like to sell a single item, say a car. A bidder may make a bid for the item at any time but expects an immediate irrevocable decision. The goal of the aucti...

Cellular radio communication is a significant contributor to battery energy drain on smartphones, in some cases inflating the energy cost by a factor of 5 or more compared to the energy cost of the base device. Stratus is a system to reduce this energy consumption by leveraging cloud resources to make data communication on smartphones more efficien...

This paper introduces a strengthening of the notion of a stable core and characterizes it in terms of Kikuta and Shapley’s extendability condition. KeywordsCo-operative games-Core-Stable sets

Cellular radios consume more power and suffer reduced data rate when the signal is weak. According to our measurements, the communication energy per bit can be as much as 6x higher when the signal is weak than when it is strong. To realize energy savings, applications must preferentially communicate when the signal is strong, either by deferring no...

We study an online version of Fisher’s linear case market. In this market there are m buyers and a set of n dividable goods to be allocated to the buyers. The utility that buyer i derives from good j is u ij . Given an allocation \(\hat{U}\) in which buyer i has utility \(\hat{U}_i\) we suggest a quality measure that is based on taking an average o...

We define a new class of markets, the Eisenberg–Gale markets. This class contains Fisher's linear market, markets from the resource allocation framework of Kelly [Kelly, F.P., 1997. Charging and rate control for elastic traffic. Europ. Transactions Telecommunications 8, 33–37], as well as numerous interesting new markets. We obtain combinatorial, s...

Cellular radio communication is a significant contributor to battery energy drain on smartphones, in some cases inflating the energy cost by a factor of 5 or more compared to the energy cost of the base device. Stratus is a system to reduce this energy consumption by leveraging cloud resources to make data communication on smartphones more efficien...

The problem of arriving at a principled method of pricing goods and services was very satisfactorily solved for conventional goods; however, this solution is not applicable to digital goods. This paper studies pricing of a special class of digital goods, which we call {\em semantically substitutable digital goods}. After taking into consideration i...

A fundamental issue in Web search is ranking search results based on user logs, since different users may have different preferences and intents with regards to a search query. Also, in many search query applications, users tend to look at only the top part of the ranked result list in order to find relevant documents. The setting we consider conta...

The next decade will see an abundance of new intelligent systems, many of which will be market-based. Soon, users will interact with many new markets, perhaps without even knowing it: when driving their car, when listening to a song, when backing up their files, or when surfing the web. We argue that these new systems can only be successful if a ne...

We consider two sided matching markets consisting of agents with non-transferable utilities; agents from the opposite sides form matching pairs (e.g., buyers-sellers) and negotiate the terms of their math which may include a monetary transfer. Competitive equilibria are the elements of the core of this game. We present the first combinatorial chara...

In the classical secretary problem an employer would like to choose the best candidate among n competing candidates that arrive in a random order. This basic concept of n elements arriving in a random order and irrevocable decisions made by an algorithm have been explored extensively over the years, and used for modeling the behavior of many proces...

When people go on the web, they surf. Accordingly, in many circumstances, such as when people use a search engine (SE) to find a "content website" (CW), the two sites are complements. Typically, both sites show advertisements to their visitors, but they do so using very different technologies. We study the incentives for such ad-funded websites wit...

The problem of arriving at a principled method of pricing goods and services was very satisfactorily solved for conventional goods; however, this solution is not applicable to digital goods. After taking into consideration idiosyncrasies of the digital realm, we give a market model that is appropriate for the digital setting, and a notion of equili...

We study bargaining networks, discussed in a recent paper of Kleinberg and Tardos [KT08], from the perspective of cooperative game theory. In particular we examine three solution concepts, the nucleolus, the core center and the core median. All solution concepts define unique solutions, so they provide testable predictions. We define a new monotoni...

We derive efficient algorithms for both detecting and representing matchings in lopsided bipartite graphs; such graphs have so many nodes on one side that it is infeasible to represent them in memory or to identify matchings using standard approaches. Detecting and representing matchings in lopsided bipartite graphs is important for allocating and...

The Internet has allowed market-based systems to become increasingly pervasive. In this paper we explore the role of user interface (UI) design for these markets. Different UIs induce different mental models which in turn determine how users understand and interact with a market. Thus, the in- tersection of UI design and economics is a novel and im...

In this paper, we propose the notion of Peer-to-Peer Human Computation, where users help each other, mediated by a platform that connects people who request help to people who offer help, acts as a repository of acquired information, and learns from users" questions and advice. We compare this idea to related ideas such as human computation and soc...

In the classical secretary problem an employer would like to choose the best candidate among n competing candidates that arrive in a random order. Our main contribution is a new linear programming technique that we introduce as a tool for obtaining and analyzing mechanisms for the secretary problem and its variants. The linear program is formulated...

We present an algorithm for the asymmetric traveling salesman problem on instances which satisfy the triangle inequality. Like several existing algorithms, it achieves approximation ratio O(log n). Unlike previous algorithms, it uses randomized rounding.

The standard solution concept for perfect-information ext ensive form games is subgame perfect Nash equilibrium. However, humans do not always play according to a subgame perfect Nash equilibrium, especially in games where it is possible for all the players to obtain much higher payof fs if they place some trust in each other (and this trust is not...

Since the link structure of the web is an important element in ranking systems on search engines, web spammers widely use the link structure of the web to increase the rank of their pages. Various link-based features of web pages have been introduced and have proven effective at identifying link spam. One particularly successful family of features...

We investigate the influence of different algorithmic choices on the approximation ratio in selfish scheduling. Our goal is to design local policies that minimize the inefficiency of resulting equilibria. In particular, we design optimal coordination mechanisms for unrelated machine scheduling, and improve the known approximation ratio from Θ(m) to...

We propose a novel viral platform for building an incentive-based off-line market for digital media. A user who owns a multimedia clip, can resell it to other end-users such that the revenue is controlled by the copyright owner. For each transaction, the seller retains part of the revenue as an in-centive for participating in the distributed econom...

We study the online ad-auctions problem introduced by Mehta et al. [15]. We design a (1 − 1/e)-competitive (optimal) algorithm for the problem, which is based on a clean primal-dual approach, matching the competitive factor obtained in [15]. Our basic algorithm along with its analysis are very simple. Our results are based on a unified approach dev...

The dimension of a partially ordered set (poset) is the minimum integer k such that the partial order can be expressed as the intersection of k total orders. We prove that there exists no polynomial-time algorithm to approximate the dimension of a poset on N elements with a factor of O(N0.5−ϵ) for any ϵ>0, unless NP=ZPP. The same hardness of approx...

We provide the first strongly polynomial time exact combinatorial algorithm to compute Fisher equilibrium for the case when utility functions do not satisfy the Gross substitutability property. The motivation for this comes from the work of Kelly, Maulloo, and Tan [15] and Kelly and Vazirani [16] on rate control in communication networks. We consid...

We consider the problem of online keyword advertising auctions among multiple bidders with limited budgets, and propose a bidding heuristic to optimize the utility for bidders by equalizing the return-on-investment for each bidder across all keywords. We show that natural auction mechanisms combined with this heuristic can experience chaotic cyclin...

We propose a scheme for building peer-to-peer overlay networks for broadcasting using network coding. The scheme addresses many practical issues such as scalability, robustness, constraints on bandwidth, and locality of decisions. We analyze the system theoretically and prove near optimal bounds on the parameters defining robustness and scalability...

Wireless LAN administrators often have to deal with the problem of sporadic client congestion in popular locations within the network. Existing approaches that relieve congestion by balancing the traffic load are encumbered by the modifications that are required to both access points and clients. We propose cell breathing, a well-known concept in c...

We provide the first polynomial time exact algorithm for computing an Arrow-Debreu market equilibrium for the case of linear utilities. Our algorithm is based on solving a convex program using the ellipsoid algorithm and simultaneous diophantine approximation. As a side result, we prove that the set of assignments at equilibria is convex and the eq...

We introduce new problems of finding minimum-cost rankings and clusterings which must be consistent with certain constraints (e.g. an input partial order in the case of ranking problems); we give deterministic approximation algorithms for these problems. Randomized approximation algorithms for unconstrained versions of these problems were given by...

We define a new class of markets, the Eisenberg-Gale markets. This class contains Fisher's linear market, markets from the resource allocation framework of Kelly kelly, as well as numerous interesting new markets.We obtain combinatorial, strongly polynomial algorithms for severalmarkets in this class. Our algorithms have a simple description as asc...

The objective of cooperative game theory is to study ways to enforce and sustain cooperation among agents willing to cooperate. A central question in this field is how the benefits (or costs) of a joint effort can be divided among participants, taking into account individual and group incentives, as well as various fairness properties. In this chap...

We study the problem of designing the hyperlink structure between the web pages of a web site in order to maximize the revenue generated from the traffic on the web site. We show this problem is equivalent to the well-studied setting of infinite horizon discounted Markov Decision Processes (MDPs). Thus existing results from that literature imply th...

The survivable network design problem (SNDP) is the following problem: given an undirected graph and values rij for each pair of vertices i and j, find a minimum-cost subgraph such that there are at least rij disjoint paths between vertices i and j. In the edge connected version of this problem (EC-SNDP), these paths must be edge-disjoint. In the v...

Given a network of lossless links with rate constraints, a source node, and a set of destination nodes, the multicast capacity is the maximum rate at which the source can transfer common information to the destinations. The multicast capacity cannot exceed the capacity of any cut separating the source from a destination; the minimum of the cut capa...

Li and Li conjectured that in an undirected network with multiple unicast sessions, network coding does not lead to any coding gain. Surprisingly enough, this conjecture could not so far be verified even for the simple network consisting of K_3,2 with four source-sink pairs. Using entropy calculus, we provide the first verification of the...

This correspondence considers the problem of distributed source coding of multiple sources over a network with multiple receivers. Each receiver seeks to reconstruct all of the original sources. The work by Ho et al. 2004 demonstrates that random network coding can solve this problem at the potentially high cost of jointly decoding the source and t...

In this paper we consider the minimum weight multicolored subgraph problem (MWMCSP), which is a common generalization of minimum cost multiplex PCR primer set selection and maximum likelihood population haplotyping. In this problem one is given an undirected graph G with non-negative vertex weights and a color function that assigns to each edge one...

Li and Li conjectured that in an undirected network with multiple unicast sessions, network coding does not lead to any coding gain. Surprisingly enough, so far this conjecture could not be verified even for the simple network consisting of K 3,2 with four source-sink pairs. Using entropy calculus, we provide the first verification of the Li-Li con...

This paper presents a practical digital signature scheme to be used in conjunction with network coding. Our scheme simultaneously provides authentication and detects malicious nodes that intentionally corrupt content on the network.

We consider information networks in the absence of interference and noise, and present an upper bound on the rate at which information can be transmitted using network coding. Our upper bound is based on combining properties of entropy with a strong information inequality derived from the structure of the network.The undirected k-pairs conjecture s...

Given a network of lossless links with rate constraints, a source node, and a set of destination nodes, the multicast capacity is the maximum rate at which the source can transfer common information to the destinations. The multicast capacity cannot exceed the capacity of any cut separating the source from a destination; the minimum of the cut capa...

We consider the computation of equilibria in two economic models that generalize the exchange model by including production. In the constant returns model, each producer has a convex, constant-returns-to-scale, technology. In particular, this means that if the technology can output a certain quantity of a good using as input certain quantities of o...

In this paper we study the prize-collecting version of the Gener- alized Steiner Tree problem. To the best of our knowledge, there is no general combinatorial techniquein approximation algorithms developed to study the prize-collecting versions of various prob- lems. These problems are studied on a case by case basis by Bien- stock et al. (5) by ap...

We study the problem of computing equilibrium prices in a Fisher market with linear utilities and linear single-constraint production units. This setting naturally appears in ad pricing where the sum of the lengths of the displayed ads is constrained not to exceed the available ad space. There are three approaches to solve market equilibrium proble...

We give a simple characterization of all single-item truth- revealing auctions under some mild (and natural) assumptions about the auctions. Our work opens up the possibility of using variational calculus to design auctions having desired properties.

In pay-per-click online advertising systems like Google, Over- ture, or MSN, advertisers are charged for their ads only when a user clicks on the ad. While these systems have many advantages over other meth- ods of selling online ads, they suffer from one major drawback. They are highly susceptible to a particular style of fraudulent attack called...

Li and Li conjectured that in an undirected network with multiple unicast sessions, network coding does not lead to any coding gain. Surprisingly enough, this conjecture could not so far be verified even for the simple network consisting of K_3,2 with four source-sink pairs. Using entropy calculus, we provide the first verification of the...

In this paper we initiate the study of the AND-OR directed feedback vertex set problem from the viewpoint of approximation algorithms. This AND-OR feedback vertex set problem is motivated by a practical deadlock resolution problem that appears in the development of distributed database systems. This problem also turns out be a natural generalizatio...

The famous max-flow min-cut theorem states that a source node s can send information through a network (V, E) to a sink node t at a rate determined by the min-cut separating s and t. Recently, it has been shown that this rate can also be achieved for multicasting to several sinks provided that the intermediate nodes are allowed to re-encode the inf...

In this paper, the network planning problem in wireless ad hoc networks is formulated as the problem of allocating physical and medium access layer resources or supplies to minimize a cost function, while fulfilling certain end-to-end communication demands, which are given as a collection of multicast sessions with desired transmission rates. We pr...

Eisenberg and Gale (1959) gave a convex program for computing market equilibrium for Fisher's model for linear utility functions, and Eisenberg (1961) generalized this to concave homogeneous functions of degree one. We further generalize to:1. Homothetic, quasi-concave utilities. This also helps extend Eisenberg's result to concave homogeneous func...

We propose a scheme for building peer-topeer overlay networks for broadcasting using network coding.The scheme addressesmany practical issues such as scalability, robustness, constraints on bandwidth, and locality of decisions. We analyze the system theoretically and prove near optimal bounds on the parameters defining robustness and scalability. A...

International audience The Road Coloring Conjecture is an old and classical conjecture e posed in Adler and Weiss (1970); Adler et al. (1977). Let $G$ be a strongly connected digraph with uniform out-degree $2$. The Road Coloring Conjecture states that, under a natural (necessary) condition that $G$ is "aperiodic'', the edges of $G$ can be colored...

The famous max-flow min-cut theorem states that a source node can send information through a network (V,E) to a sink node at a rate determined by the min-cut separating s and t. Recently, it has been shown that this rate can also be achieved for multicasting to several sinks provided that the intermediate nodes are allowed to re-encode the informat...

We prove the existence of tolls to induce multicommodity, heterogeneous network users that independently choose routes minimizing their own linear function of tolls versus latency to collectively form the traffic pattern of a minimum average latency flow. This generalizes both the previous known results of the existence of tolls for multicommodity,...

Efficient integration of a multi-hop wireless network with the Internet is an important research problem. In a wireless neighborhood network, a few Internet transit access points (ITAPs), serving as gateways to the Internet, are deployed across the neighborhood; houses are equipped with low-cost antennas, and form a multi-hop wireless network among...

The survivable network design problem (SNDP) is the following problem: given an undirected graph and values r ij for each pair of vertices i and j, find a minimum-cost subgraph such that there are r ij disjoint paths between vertices i and j. In the edge connected version of this problem (ECSNDP) , these paths must be edge-disjoint. In the vertex c...

The element connectivity problem falls in the category of survivable network design problems -- it is intermediate to the versions that ask for edge-disjoint and vertex-disjoint paths. The edge version is by now well understood from the view-point of approximation algorithms [17, 5, 8], but very little is known about the vertex version. In our prob...

In this paper, we investigate the throughput achiev-able for multiple multicast sessions in a wireless ad hoc network. We propose an iterative cross-layer optimization, which alternates between a linear optimization that jointly coordinates the flow assignment for network coding and timesharing in the MAC layer, and a heuristic scheme for updating...

allocating information carrier supplies such that certain end-to-end communication demands, as a collection of multicast sessions, are fulfilled. This formulation necessitates a cross-layer coupling. We aim at a computational characterization of the performance theoretically achievable with joint optimizations spanning the network stack.

Network coding solutions and routing solutions, namely packing distribution trees, for the problem of information multicast is compared in this paper. To enable the comparison, we develop greedy tree packing algorithms that repeatedly pack the maximum-rate distribution tree and a greedy tree packing algorithm based on Lovasz' proof to Edmonds' theo...

In wireless networks, an attacker can tune a receiver and tap the communication between two nodes. Whether or not some meaningful information is obtained by tapping a wireless connection depends the security protocols used. One may use cryptographic techniques to secure the communications. In this article we discuss an alternate way of securing the...

We consider a fault tolerant version of the metric facility location problem in which every city, j, is required to be connected to r j facilities. We give the first non-trivial approximation algorithm for this problem, having an approximation guarantee of 3 · H k , where k is the maximum requirement and H k is the kth harmonic number. Our algo...

Congestion is a natural phenomenon in any network queuing system, and is unavoidable if the queuing system is operated near capacity. In this paper we study how to set the rules of a queuing system so that all the users have a self-interest in controlling congestion when it happens.Routers in the internet respond to local congestion by dropping pac...