Results 1  10
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45
Scheduling of Virtual Connections in Fast Networks
 In Proc. of Parallel Systems and Algorithms (PASA
, 1996
"... this paper, we assume that all call requests are available at time 0 and do not have to be completed by a certain deadline. There is no precedence relation among the calls. We consider the offline version of the problem, where call durations are known in advance. In section 2 and 3 we restrict our ..."
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Cited by 50 (6 self)
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this paper, we assume that all call requests are available at time 0 and do not have to be completed by a certain deadline. There is no precedence relation among the calls. We consider the offline version of the problem, where call durations are known in advance. In section 2 and 3 we restrict our attention to the case that all edges have unit capacity, all calls require unit bandwidth, and all call durations are the same (unit duration). In section 4 we present some results for the more general setting of arbitrary call durations and arbitrary bandwidth requirements.
An experimental study of data migration algorithms. Algorithm Engineering
 the Proceedings of WAE 2001: 5th Workshop on Algorithm Engineering (BRICS, University of Aarhus
, 2001
"... Abstract. The data migration problem is the problem ofcomputing a plan for moving data objects stored on devices in a network from one configuration to another. Load balancing or changing usage patterns might necessitate such a rearrangement ofdata. In this paper, we consider the case where the obje ..."
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Cited by 48 (5 self)
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Abstract. The data migration problem is the problem ofcomputing a plan for moving data objects stored on devices in a network from one configuration to another. Load balancing or changing usage patterns might necessitate such a rearrangement ofdata. In this paper, we consider the case where the objects are fixedsize and the network is complete. We introduce two new data migration algorithms, one ofwhich has provably good bounds. We empirically compare the performance of these new algorithms against similar algorithms from Hall et al. [7] which have better theoretical guarantees and find that in almost all cases, the new algorithms perform better. We also find that both the new algorithms and the ones from Hall et al. perform much better in practice than the theoretical bounds suggest. 1
Software complexity
 Crosstalk, Journal of Defense Software Engineering
, 1994
"... The edge coloring problem asks for assigning colors from a minimum number of colors to edges of a graph such that no two edges with the same color are incident to the same node. We give polynomial time algorithms for approximate edge coloring of multigraphs, i.e., parallel edges are allowed. The bes ..."
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Cited by 42 (0 self)
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The edge coloring problem asks for assigning colors from a minimum number of colors to edges of a graph such that no two edges with the same color are incident to the same node. We give polynomial time algorithms for approximate edge coloring of multigraphs, i.e., parallel edges are allowed. The best previous algorithms achieve a fixed constant approximation factor plus a small additive offset. One of our algorithms achieves solution quality opt + � 9opt/2 and has execution time polynomial in the number of nodes and the logarithm of the maximum edge multiplicity.
Algorithms for Data Migration with Cloning
, 2003
"... Our work is motivated by the problem of managing data on storage devices, typically a set of disks. Such high demand storage servers are used as web servers, or multimedia servers for handling high demand for data. As the system is running, it needs to dynamically respond to changes in demand for di ..."
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Cited by 32 (4 self)
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Our work is motivated by the problem of managing data on storage devices, typically a set of disks. Such high demand storage servers are used as web servers, or multimedia servers for handling high demand for data. As the system is running, it needs to dynamically respond to changes in demand for di#erent data items. In this work we study the data migration problem, which arises when we need to quickly change one storage configuration into another. We show that this problem is NPhard. In addition, we develop polynomialtime approximation algorithms for this problem and prove a worst case bound of 9.5 on the approximation factor achieved by our algorithm. We also compare the algorithm to several heuristics for this problem.
Call Scheduling in Trees, Rings and Meshes
 In Proc. of HICSS
, 1997
"... The problem of establishing and completing a given set of calls as early as possible is studied for bidirectional and directed calls in various classes of networks. Even under the assumption of unit bandwidth requirements and unit call durations, call scheduling is NP–hard for trees with unbounded d ..."
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Cited by 31 (5 self)
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The problem of establishing and completing a given set of calls as early as possible is studied for bidirectional and directed calls in various classes of networks. Even under the assumption of unit bandwidth requirements and unit call durations, call scheduling is NP–hard for trees with unbounded degree, for rings, and for meshes. Whereas bidirectional calls can be scheduled optimally in polynomial time for trees of constant degree, the problem for directed calls is already NP–hard for binary trees. Approximation algorithms with constant performance ratio are known for many NP–hard variants of call scheduling. 1
On the Wavelength Assignment Problem in Multifiber WDM Star and Ring Networks
 IEEE Infocom
, 2000
"... This paper studies the offline wavelength assignment problem in star and ring networks that deploy multiple fibers between nodes and use Wavelength Division Multiplexing (WDM) for transmission. The results in this paper show that the ability to switch between fibers increases wavelength utilization ..."
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Cited by 23 (1 self)
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This paper studies the offline wavelength assignment problem in star and ring networks that deploy multiple fibers between nodes and use Wavelength Division Multiplexing (WDM) for transmission. The results in this paper show that the ability to switch between fibers increases wavelength utilization. In particular, sharper perfiber bounds on the number of required wavelengths are derived for the multifiber version of the assignment problem in star and ring networks. Additionally, the complexity of the problem is studied and several constrained versions of the problem are also considered for star and ring networks. A summary of contributions is provided in the first section. 1 Introduction Optical networks hold out the promise of meeting the high transmission quality and large bandwidth desired by enduser applications. Among various transmission technologies for optical networks, Wavelength Division Multiplexing (WDM), because of its efficient use of bandwidth, has received consider...
The Complexity of Path Coloring and Call Scheduling
 Theoretical Computer Science
, 2000
"... Modern highperformance communication networks pose a number of challenging problems concerning the efficient allocation of resources to connection requests. In alloptical networks with wavelengthdivision multiplexing, connection requests must be assigned paths and colors (wavelengths) such that i ..."
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Cited by 22 (6 self)
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Modern highperformance communication networks pose a number of challenging problems concerning the efficient allocation of resources to connection requests. In alloptical networks with wavelengthdivision multiplexing, connection requests must be assigned paths and colors (wavelengths) such that intersecting paths receive different colors, and the goal is to minimize the number of colors used. This path coloring problem is proved NPhard for undirected and bidirected ring networks. Path coloring in undirected tree networks is shown to be equivalent to edge coloring of multigraphs, which implies a polynomialtime optimal algorithm for trees of constant degree as well as NPhardness and an approximation algorithm with absolute approximation ratio 4:3 and asymptotic approximation ratio 1:1 for trees of arbitrary degree. For bidirected trees, path coloring is shown to be NPhard even in the binary case. A polynomialtime optimal algorithm is given for path coloring in undirected or bidir...
OffLine and OnLine CallScheduling in Stars and Trees
 in Proceedings of the 23rd International Workshop on GraphTheoretic Concepts in Computer Science, WG ‘97, LNCS1335, SpringerVerlag
, 1997
"... . Given a communication network and a set of call requests, the goal is to find a minimum makespan schedule for the calls such that the sum of the bandwidth requirements of simultaneously active calls using the same link does not exceed the capacity of that link. In this paper the callschedulin ..."
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Cited by 11 (2 self)
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. Given a communication network and a set of call requests, the goal is to find a minimum makespan schedule for the calls such that the sum of the bandwidth requirements of simultaneously active calls using the same link does not exceed the capacity of that link. In this paper the callscheduling problem is studied for star and tree networks. Lower and upper bounds on the worstcase performance of ListScheduling (LS) and variants of it are obtained for callscheduling with arbitrary bandwidth requirements and either unit call durations or arbitrary call durations. LS does not require advance knowledge of call durations and, hence, is an online algorithm. It has performance ratio (competitive ratio) at most 5 in star networks. A variant of LS for calls with unit durations is shown to have performance ratio at most 2 2 3 . In tree networks with n nodes, a variant of LS for calls with unit durations has performance ratio at most 6, and a variant for calls with arbitrary d...
Approximation Hardness for Small Occurrence Instances of NPHard Problems
, 2002
"... The paper contributes to the systematic study (started by Berman and Karpinski) of explicit approximability lower bounds for small occurrence optimization problems. We present parametrized reductions for some packing and covering problems, including 3Dimensional Matching, and prove the best know ..."
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Cited by 9 (0 self)
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The paper contributes to the systematic study (started by Berman and Karpinski) of explicit approximability lower bounds for small occurrence optimization problems. We present parametrized reductions for some packing and covering problems, including 3Dimensional Matching, and prove the best known inapproximability results even for highly restricted versions of them. For example, we show that it is NPhard to approximate Max3DM within 141 140 even on instances with exactly two occurrences of each element.