Wolfgang W. Bein

• Dr. rer. nat. (Ph.D.)
• Professor (Full) at University of Nevada, Las Vegas

We consider the classical power management problem: There is a device which has two states ON and OFF and one has to develop a control algorithm for changing between these states as to minimize (energy) cost when given a sequence of service requests. Although an optimal 2-competitive algorithm exists, that algorithm does not have good performance i...

Algorithms for series-parallel graphs can be extended to arbitrary two-terminal dags if node reductions are used along with series and parallel reductions. A node reduction contracts a vertex with unit in-degree (out-degree) into its sole incoming (outgoing) neighbor. This paper gives an O(n2"5) algorithm for minimizing node reductions, based on ve...

Many open source software projects are not very open to third party developers. The point of open source is to enable anyone to fix bugs or add desired capabilities without holding them hostage to the original developers. This principle is important because an open source project's developers may be unresponsive or unable to meet third party needs,...

We study the concept of series and parallel composition of linear programming problems and show that greedy properties are inherited by such compositions. Our results are inspired by earlier work on compositions of flow problems. We make use of certain Monge properties as well as convexity properties which support the greedy method in other context...

We introduce the novel concept of knowledge states. The knowledge state approach can be used to construct competitive randomized online algorithms and study the trade-off between competitiveness and memory. Many well-known algorithms can be viewed as knowledge state algorithms. A knowledge state consists of a distribution of states for the algorith...

Problems addressing the generation of random polygons have important applications for evaluating the performance of algorithms on polygonal domains. The standard Voronoi diagram can be applied effectively to determine the service regions of battery exchange stations when all service exchange stations have identical capacity. In real world situation...

We consider a power-down system with two states—“on” and “off”—and a continuous set of power states. The system has to respond to requests for service in the “on” state and, after service, the system can power off or switch to any of the intermediate power-saving states. The choice of states determines the cost to power on for subsequent requests....

We consider the classical power management problem: There is a system or “device” which has two states—ON and OFF—and one has to develop a control algorithm for changing between these states as to minimize cost (energy or some other hybrid cost) when given a sequence of service requests. We analyze this problem in terms of online competitive analys...

Power-down mechanisms are well known and are widely used to save energy; these mechanisms are encountered on an everyday basis. We consider a device which has a set of states defined by a continuous function. The state of the device can be switched at any time. In any state the device consumes energy and a power up cost to switch the machine to ful...

In this paper, we study the grid scheduling problem in a battery exchange station (BES) as a part of the battery consolidation system (BCS). We define the grid scheduling problem as the BES's service scheduling to exchange batteries of electric vehicles (EVs), the battery exchange price scheduling, and the electricity buying scheduling for a day ah...

Passenger routing in railway systems has traditionally relied on fixed timetables, working under the assumption that actual performance always matches the planned schedules. The complex variable interplay found in railway networks, however, make it practically impossible for trains to systematically hold the designed timetables as delays are a comm...

When people suffer from issues like workplace stress, financial stress, marital stress, family stress, bullying, domestic violence, peer pressure, anxiety, relationship issues, career issues, parenting, loneliness, depression and others, they try to avoid it, either by saying life is just like this or by comparing their problems with others. Distra...

The concept of the battery exchange station (BES) as a part of the battery consolidation system (BCS) has certain criteria which makes it a significant player of bettery adaptation plan of electric vehicles (EVs) in the grid toward the smart grid (SG). In this paper, we focus on finding an efficient joint capacity and placement planning of BESs amo...

Power-down mechanisms are well known and are widely used to save energy; these mechanisms are encountered on an everyday basis. We consider a device which has a set of states defined by a continuous function. The state of the device can be switched at any time. In any state the device consumes energy and a power up cost to switch the machine to ful...

During the past decade, the smart grid (SG) concept has been advancing better global acceptance of the electric vehicle (EV) notion. Additionally, the incorporation of renewable energy (RE) resources in the SG is a promising solution to reduce carbon emissions in an intelligent manner. Due to technological barriers at this moment, battery charging...

A power-down system has an on-state, an off-state, and a finite or infinite number of intermediate states. In the off-state, the system uses no energy and in the on-state energy it is used fully. Intermediate states consume only some fraction of energy but switching back to the on-state comes at a cost. Previous work has mainly focused on asymptoti...

Power-down mechanisms are well known and are widely used to save energy. We consider a device which has states OFF, ON, and a fixed number of intermediate states. The state of the device can be switched at any time. In the OFF state the device consumes zero energy and in ON state it works at its full power consumption. The intermediate states consu...

Today’s recruitment applications are designed not only reduce paperwork but can make a significant contribution to a company’s marketing and sales activity. Recruitment websites and software make possible for managers to access information crucial to managing their staff, which they can use for promotion decisions, payroll considerations and hiring...

The mini-track “Decision Support for Complex Networks” invited contributions in the area of complex decision support under multiple criteria and where a multitude of variables have to be considered under great uncertainty. Typically, such systems are used for crisis and risk management in diverse contexts, such as health care, homeland security, av...

Theme The International Conference on Information Technology-New Generations (ITNG) is an annual event focusing on state of the art technologies pertaining to digital information and communications. The applications of advanced information technology to such domains as astronomy, biology, education, geosciences, health care and security are among t...

In this paper, the frequency of trains in the Munich subway network is analyzed. Using influence diagrams the stations and edges in the network that are most vulnerable to catastrophic attacks are determined. Upon obtaining the number of trains in each station at a certain moment in time, the most vulnerable stations will be automatically identifie...

We explore options for integrating sustainable and renewable energy into the existing power grid, or even create a new power grid model. We present various theoretical concepts necessary to meet the challenges of a smart grid. We first present a supply and demand model of the smart grid to compute the average number of conventional power generator...

The black and white bin packing problem is a variant of the classical bin packing problem, where in addition to a size, each item also has a color (black or white), and in each bin the colors of items must alternate. The problem has been studied extensively, but the best competitive online algorithm has competitiveness of 3. The competitiveness of...

Power-down mechanisms are well known and are widely used to save energy, these mechanisms are encountered on an everyday basis. We consider a device which has states OFF, ON, and a fixed number of intermediate states. The state of the device can be switched at any time. In the OFF state the device consumes zero energy and in ON state it works at it...

The most common approach for border patrol operations is the use of human personnel and manned ground vehicles, which is expensive, at times inefficient and sometimes even hazardous to people involved. A better approach would be using Unmanned Aerial Vehicles (UAVs) in combination with such ground sensors. This would help improve the overall effect...

This paper introduces the use of conditional-value-at-risk (CVaR) as a criterion for stochastic scheduling problems. This criterion has the tendency of simultaneously reducing both the expectation and variance of a performance measure, while retaining ...

This is an overview over dynamic programming with an emphasis on advanced methods. Problems discussed include path problems, construction of search trees, scheduling problems, applications of dynamic programming for sorting problems, server problems, as well as others. This chapter contains an extensive discussion of dynamic programming speedup. Th...

A randomized on-line algorithm is given for the 2-server problem on the line, with competitiveness less than 1.901 against the oblivious adversary. This improves the previously best known competitiveness of 15578 ≈ 1.987 for the problem. The algorithm uses a new approach and defines a potential in terms of isolation indices from T-theory.

The minitrack on Open Movements is introduced.

Block sorting is used in connection with Optical Character Recognition (OCR). Recent work has focused on finding good strategies which work in practice. In this paper, we show that optimizing block sorting is ${\mathcal {NP}}$-hard. Along with this result, we give new non-trivial lower bounds. These bound can be computed efficiently. We define the...

It has been a long-standing open problem to determine the exact randomized competitiveness of the 2-server problem, that is, the minimum competitiveness of any randomized online algorithm for the 2-server problem. For deterministic algorithms the best competitive ratio that can be obtained is 2 and no randomized algorithm is known that improves thi...

We study the problem of allocating memory of servers in a data center based on online requests for storage. Given an online sequence of storage requests and a cost associated with serving the request by allocating space on a certain server one seeks to select the minimum number of servers as to minimize total cost. We use two different algorithms a...

Large corporations such as Amazon, Google, Microsoft, and Yahoo, use data centers to keep up with the growing demand for communication-hungry Internet services like image and video sharing, social networking, and searching. We study the problem of actually allocating the memory of servers in a data center based on online requests for storage. Given...

Batching has been studied extensively in the offline case, but applications such as manufacturing or TCP acknowledgment often require online solutions.We consider online batching problems, where the order of jobs to be batched is fixed and where we seek to minimize the sum of the completion times of the jobs. We present optimally competitive online...

We consider the online list s-batch problem, where all the jobs have processing time 1 and we seek to minimize the sum of the completion times of the jobs. We give a Java program which is used to verify that the competitiveness of this problem is 619/583.

The block sorting problem is the problem of minimizing the number of steps to sort a list of distinct items, where a sublist of items which are already in sorted order, called a block, can be moved in one step. We give an approximation algorithm for the block sorting problem with an approximation ratio of and run time . The approximation algorithm...

Multiprocessor systems with a global shared memory provide logically uniform data access. To hide latencies when accessing global memory each processor makes use of a private cache. Several copies of a data item may exist concurrently in the system. To guarantee consistency when updating an item a processor must invalidate copies of the item in oth...

We study the coverage problem for sensor networks from the fault tolerance and reliability point of view. Fault tolerance is a critical issue for sensors deployed in places where they are not easily replaceable, repairable and rechargeable. Failure of one node should not incapacitate the entire network. We propose three 1-fault tolerant topologies,...

Suppose there are n applications and n processors. A pair cover is a set S of one-to-one mappings (assignments) of the applications to the processors such that, for every pair (Ai,Aj) of applications and every pair (p,q) of processors, there is an assignment f in S that maps (Ai,Aj) to (p,q). More generally, we consider, for all k/spl ges/1, minimu...

A technique for clustering data by common attribute values involves grouping rows and columns of a binary matrix to make the minimum number of submatrices all 1's. As binary matrices can be viewed as adjacency matrices of bipartite graphs, the problem is equivalent to partitioning a bipartite graph into the smallest number of complete bipartite sub...

We prove that there exists a randomized online algorithm for the 2-server 3-point problem whose expected competitive ratio is at most 1.5897. This is the first nontrivial upper bound for randomized k-server algorithms in a general metric space whose competitive ratio is well below the corresponding deterministic lower bound (= 2 in the 2-server cas...

We prove that there exists a randomized online algorithm for the 2-server 3-point problem whose expected competitive ratio is at most 1.5897. This is the first nontrivial upper bound for randomized k-server algorithms in a general metric space whose competitive ratio is well below the corresponding deterministic lower bound (= 2 in the 2-server cas...

In scheduling, the two machine flow shop problem F2parSigma C_i is to find a schedule that minimizes the sum of finishing times of an arbitrary number of jobs that need to be executed on two machines, such that each job must complete processing on machine 1 before starting on machine 2. Finding such a schedule is NP-hard [6]. We propose a...

The bin packing with rejection problem is the following: Given a list of items with associated sizes and rejection costs, find a packing into unit bins of a subset of the list, such that the number of bins used plus the sum of rejection costs of unpacked items is minimized. In this paper, we first show that bin packing with rejection can be reduced...

In ubiquitous computing the user is surrounded by many computational devices and systems Ordinary actions and different parameter values of the environment being sensed by these devices trigger actions of which the user may not necessarily be aware Privacy protection as part of network security refers to the protection of sensitive, personal inform...

We give a randomized algorithm (the “Wedge Algorithm”) of competitiveness 32Hk−12k for any metrical task system on a uniform space of k points, for any k⩾2, where Hk=∑i=1k1i, the kth harmonic number. This algorithm has better competitiveness than the Irani–Seiden algorithm if k is smaller than 108. The algorithm is better by a factor of 2 if k47.

It has been a long-standing open problem to determine the exact randomized competitiveness of the 2-server problem, that is, the minimum competitiveness of any randomized online algorithm for the 2-server problem. For deterministic algorithms the best competitive ratio that can be obtained is 2 and no randomized algorithm is known that improves thi...

The randomized k-paging algorithm Equitable given by Achlioptas et al. is H k -competitive and uses O(k 2 logk) memory. This competitive ratio is best possible. The randomized algorithm RMark given by Fiat et al. is (2H k − 1)-competitive, but only uses O(k) memory. Borodin and El Yaniv [6] list as an open question whether there exists an H k -comp...

We introduce the concept of knowledge states; many well-known algorithms can be viewed as knowledge state algorithms. The knowledge state approach can be used to to construct competitive randomized online algorithms and study the tradeoff between competitiveness and memory. A knowledge state simply states conditional obligations of an adversary, by...

“Bin packing with rejection” is the following problem: Given a list of items with associated sizes and rejection costs, find a packing into unit bins of a subset of the list such that the number of bins used plus the sum of rejection costs of unpacked items is minimized. We show that bin packing with rejection can be reduced to n multiple knapsack...

When employed by a company, in almost all the cases a new employee has to sign an agreement giving the company exclusive rights to any intellectual property developed as part of their work assignments. This agreement could extend beyond a change of jobs and cause conflict of interests in new employment situations. A patent is a government-granted m...

A copyright provides protection for original artistic or literary work and is valid for the life of the owner plus 70 years. There is a growing tension between creative practices that require access to content that is often copyrighted, and increasingly restrictive intellectual property laws and policies governing access to copyrighted content. Ver...

We consider here the one-machine serial batching problem under weighted average completion. This problem is known to be $cal Ncal P$-hard and no good approximation algorithms are known. Batching has wide application in manufacturing, decision management, and scheduling in information technology.We give an approximation algorithm with approximation...

There exist several general techniques in the literature for speeding up naive implementations of dynamic programming. Two of the best known are the Knuth-Yao quadrangle inequality speedup and the SMAWK algorithm for finding the row-minima of totally monotone matrices. Although both of these techniques use a quadrangle inequality and seem similar,...

We introduce a new version of the server problem: the delayed server problem. In this problem, once a server moves to serve a request, it must wait for one round to move again, but could serve a repeated request to the same point. We show that the delayed k-server problem is equivalent to the (k–1)-server problem in the uniform case, but not in gen...

Block sorting is used in connection with optical character recognition (OCR). Recent work has focused on finding good strategies which perform well in practice. Block sorting is \(\mathcal{NP}\)-hard and all of the previously known heuristics lack proof of any approximation ratio. We present here an approximation algorithm for the block sorting pro...

We study the coverage problem from the fault tolerance point of view for sensor networks. Fault tolerance is a critical issue for sensors deployed in places where are not easily replaceable, repairable and rechargeable. The failure of one node should not incapacitate the entire network. We propose three 1 fault tolerant models, and we compare them...

We give algorithmic results for combinatorial problems with cost arrays possessing certain algebraic Monge properties. We extend Monge-array results for two shortest path problems to a general algebraic setting, with values in an ordered commutative semigroup, if the semigroup operator is strictly compatible with the order relation.We show how our...

We give a randomized algorithm (the "Wedge Algorithm") of competitiveness for any metrical task system on a uniform space of k points. This algorithm has better competitiveness than the Irani-Seiden algorithm if k is smaller than 10⁸. The algorithm is better by a factor of 2 if k < 47.

We introduce the novel concept of knowledge states. A knowledge state simply states conditional obligations of an adversary, by fixing a work function, and gives a distribution for the algorithm. When a knowledge state algorithm receives a request, it then calculates one or more “subsequent” knowledge states, together with a probability of transiti...

We present an optimal embedding of a honeycomb network (honeycomb mesh and honeycomb torus) of size n into a hypercube with expansion ratio of 4/3 ≈ 1.33 when n is a power of two. When n is not a power of two, the expansion is 16/3 ≈ 5.33, which we conjecture to be near optimal. For a honeycomb mesh, the dilation of the embedding is 1. For a honeyc...

Batching has been studied extensively in the offline case, but many applications such as manufacturing or TCP acknowledgement require online solutions. We consider online batching problems, where the order of jobs to be batched is fixed and where we seek to minimize average flow time. We present optimally competitive algorithms for s-batch (compet...

We describe total congestion 1 embeddings of complete binary trees into three dimensional grids with low expansion ratio r. That is, we give a one-to-one embedding of any complete binary tree into a hexahedron shaped grid such that (a) the number of nodes in the grid is at most r times the number of nodes in the tree, and (b) no tree nodes or edges...

Multiprocessor systems with a global shared memory provide logically uniform data access. To hide latencies when accessing global memory each processor makes use of a private cache. Several copies of a data item may exist concurrently in the system. To guarantee consistency when updating an item a processor must invalidate copies of the item in oth...

In the k-server problem we wish to minimize, in an online fashion, the movement cost of k servers in response to a sequence of requests (we assume that k greater than or equal to 2). The request issued at each step is specified by a point r in a given metric space M. To serve this request, one of the k servers must move to r. It is known that if M...

We present an efficient algorithm called the Quadtree Heuristic for identifying a list of similar terms for each unique term in a large document collection. Term similarity is defined using the expected mutual information measure (EMIM). Since our aim for defining the similarity lists is to improve information retrieval (IR), we present the outcome...

When restricted to cost arrays possessing the sum Monge property, many combinatorial optimization problems with sum objec- tive functions become significantly easier to solve. The more general algebraic assignment and transportation problems are similarly easier to solve given cost arrays possessing the corresponding algebraic Monge property. We sh...

We describe total congestion 1 embeddings of complete binary trees into three dimensional grids with a fixed number of layers. More specifically, we give a one-to-one embedding of any complete binary tree into a hexahedron shaped grid such that no tree nodes or edges occupy the same grid positions. With 7 layers, the number of nodes in the grid is...

Block sorting is used in connection with optical character recognition (OCR). Recent work has focused on finding good strategies which work in practice. We show that optimizing block sorting is NP-hard. Along with this result, we give new non-trivial lower bounds. These bounds can be computed efficiently. We define the concept of local property alg...

An efficient randomized online algorithm for the paging problem for cache size 2 is given, which is -competitive against an oblivious adversary. The algorithm keeps track of at most one page in slow memory at any time. A lower bound of is given for the competitiveness of any trackless online algorithm for the same problem, i.e., an algorithm that k...

A class of "simple" online algorithms for the k-server problem is identified. This class, for which the term trackless is introduced, includes many known server algorithms. The k-server conjecture fails for trackless algorithms. A lower bound of 23/11 on the competitiveness of any deterministic trackless 2-server algorithm and a lower bound of 1 +...

We describe total congestion 1 embeddings of complete binary trees into three dimensional grids with expansion ratios 1.172 and 1.25. That is, we give a one-to-one embedding of any complete binary tree into a hexahedron shaped grid such that: the number of nodes in the grid is at most 1.172 (1.25) times the number of nodes in the tree; and no tree...

In the k-Server Problem we wish to minimize, in an online fashion, the movement cost of k servers in response to a sequence of requests. The request issued at each step is specified by a point r in a given metric space M. To serve this request, one of the k servers must move to r. (We assume that k ≥ 2.) It is known that if M has at least k + 1 poi...

In the k-Server Problem we wish to minimize, in an online fashion, the movement cost of k servers in response to a sequence of requests. The request issued at each step is speciied by a point r in the given metric space, and one of the k servers must be moved to r. An online algorithm for this problem is called C-competitive if its cost on any requ...

The concept of tracklessness , an information flow restriction for online algorithms, similar in some sense to memorylessness, is introduced. A number of well-known algorithms are trackless, for example, BALANCE and HARMONIC. New lower bounds are obtained for the competitiveness of trackless algorithms for the 2-server problem. An open question by...

When restricted to cost arrays possessing the sum Monge property, many combinatorial optimization problems with sum objective functions become significantly easier to solve. (An array A = fa[i; j]g possesses the sum Monge property if for all i ! k and j ! `, a[i; j] + a[k; `] a[i; `] + a[k; j].) Examples include the usual sum-objective-function ver...

. Algorithms for series-parallel graphs can be extended to arbitrary two-terminal dags if node reductions are used along with series and parallel reductions. A node reduction contracts a vertex with unit in-degree (out-degree) into its sole incoming (outgoing) neighbor. We give an O(n 2:5 ) algorithm for minimizing node reductions, based on vertex...

In 1963, Hoffman gave necessary and sufficient conditions under which a family of O(mn)-time greedy algorithms solves the classical two-dimensional transportation problem with m sources and n sinks. One member of this family, an algorithm based on the “northwest corner rule”, is of particular interest, as its running time is easily reduced to O(m +...

The support of Boolean set operations in free-form solid modeling systems requires the repeated intersection of parametric surfaces. Present approaches to this problem are sequential and must make trade-offs between accuracy, robustness and efficiency. In this paper, we investigate a parallel approach to the surface intersection problem that shows,...

When restricted to cost arrays possessing the sum Monge property, many combinatorial optimization problems with sum objective functions become significantly easier to solve. Examples include the usual sum-objective-function versions of the assignment problem, the transportation problem, the traveling-salesman problem, and several shortest-path prob...

A complete edge-weighted directed graph on vertices 1,2,...,n that assigns cost c(i,j) to the edge (i,j) is called Monge if its edge costs form a Monge array, i.e., for all i < k and j < l, c[i, j]+c[k,l]{le} < c[i,l]+c[k,j]. One reason Monge graphs are interesting is that shortest paths can be computed quite quickly in such graphs. In particular,...

Meggido [1974] showed that the maximum flow through sets of sources in a multiple sink flow network is a polymatroidal function. Recently, Federgruen and Groenevelt [1985], [1986] have considered polymatroids that can be represented by a multiple source flow network and have improved the runnung time of an important scheduling application. We give...