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We say an algorithm on n × n matrices with entries in [-M, M] (or n-node graphs with edge weights from [-M, M]) is truly subcubic if it runs in O(n3-δ - poly(log M)) time for some δ > 0. We define a notion of subcubic reducibility, and show that many important problems on graphs and matrices solvable in O(n3) time are equivalent under subcubic reductions. Namely, the following weighted problems...
We give a subexponential time approximation algorithm for the Unique Games problem. The algorithms run in time that is exponential in an arbitrarily small polynomial of the input size, nε. The approximation guarantee depends on ε, but not on the alphabet size or the number of variables. We also obtain a subexponential algorithms with improved approximations for SMALL-SET EXPANSION and MULTICUT. For...
Quality of service (QoS) provisioning generally assumes more than one QoS measure which implies that QoS routing can be categorized as an instance of routing subject to multiple constraints: delay-jitter, bandwidth, cost, etc. We study the problem of constructing multicast trees to meet the QoS requirements of real-time interactive applications where it is necessary to provide bounded delays and bounded...
The partition clustering problem is the one of the hardest problems in nowadays research. Also Partition clustering problem is the basic problem in data mining. In most cases, the partition clustering algorithm is NP problem. In this paper, there introduced an algorithm to solve partition clustering problem in polynomial time by using some reduction technology. This algorithm is availability after...
Currently, community detection has led to a huge interest in data analysis on real-world networks. However, the high computationally demanding of most community detection algorithms limits their applications. In this paper, we propose a heuristic algorithm to extract the community structure in large networks based on local community attractive force optimization whose time complexity is near linear...
This paper discusses the analytical and computational challenges of various sub-gradient and cutting plane methods applied to updating Lagrangian multipliers associated with the Security-Constrained Unit Commitment problem. Large-scale testing systems are used to demonstrate the effectiveness of the different algorithms.
In this paper, we study resource allocation and relay selection in a decode-and-forward downlink OFDMA cooperative network assuming imperfect channel state information (CSI) at the base station (BS). We assume that due to feedback delay, the BS has only outdated CSI of BS to users and inter-user links. We propose a centralized optimization framework in which the BS takes decisions on the basis of...
Power control has been extensively studied as an important way of mitigating interference and providing minimum signal to interference plus noise ratio (SINR) guarantees. Such formulation of power control is well-motivated in cellular PCS and UMTS, as both voice and streaming media require guaranteed short-term rates. A key difficulty is that the problem can easily become infeasible, implying that...
This paper deals with dynamic resource allocation problem for OFDMA-based cognitive radio systems. The proposed solution is specifically tailored for a secondary base stations (SBS) transmitting to secondary users (SUs) over the same bands of the licensed primary users (PUs) in underlay fashion. The downlink transmission goodput is thereby maximized while keeping the interference on the PUs within...
This paper deals with collision avoidance problems while following an optimal trajectory for a group of agents operating in open space. The basic idea is to use the Model Predictive Control (MPC) technique to solve a realtime optimization problem with non-convex constraints over a finite time horizon. Both centralized and decentralized MPC formulations are presented. In a second stage it is shown...
Software Testing is one of the indispensable parts of the software development lifecycle and structural testing is one of the most widely used testing paradigms to test various software. Structural testing relies on code path identification, which in turn leads to identification of effective paths. Aim of the current paper is to present a simple and novel algorithm with the help of an ant colony optimization,...
NAND flash memories are the most widely used non-volatile memories, and data movement is common in flash storage systems. We study data movement solutions that minimize the number of block erasures, which are very important for the efficiency and longevity of flash memories. To move data among n blocks with the help of ?? auxiliary blocks, where every block contains m pages, we present algorithms...
Recent advances in microelectronic technology have made it possible to construct compact and inexpensive wireless sensors. Sensor networks have received significant attention due to their potential applications from civil to military domains. Since sensors in sensor networks are equipped with energy-limited batteries, energy conservation in such networks is of paramount importance in order to prolong...
The concept of context tree, usually defined for finite memory processes, is extended to arbitrary stationary ergodic processes (with finite alphabet). These context trees are not necessarily complete, and may be of infinite depth. The familiar BIC and MDL principles are shown to provide strongly consistent estimators of the context tree, via optimization of a criterion for hypothetical context trees...
In this paper, a combinatorial auction problem is modeled as a NP-complete set packing problem and a Lagrangian relaxation based heuristic algorithm is proposed. Extensive experiments are conducted using benchmark CATS test sets and more complex test sets. The algorithm provides optimal solutions for most test sets and is always 1%from the optimal solutions for all CATS test sets. Comparisons with...
This paper was motivated by recent research in placement algorithms for VLSI circuits and attempts to visualize the connectivity and underlying physics associated with large networks or Internets. In both cases, these are graph problems made difficult by the inherent complexity of the problem (NPC) in conjunction with the size of the problem. In this work we present two useful alternatives for the...
This paper is interested in reward maximization of periodic real-time tasks under a given energy constraint, where the reward received depends on how much computation a task runs before its deadline. When voltage scaling could be done at any time, and tasks share the same power consumption function, we propose a greedy algorithm which derives a solution with at least a half of the optimal reward for...
In this paper we consider algorithms for the logical topology design and traffic grooming problem in WDM networks with router interface constraints as well as optical constraints. The optical constraints include restricted transmission range due to optical impairments as well as limits on the number of available wavelengths. We formulate this problem as an integer linear program which is NP-complete...
Various network monitoring and performance evaluation schemes generate considerable amount of traffic, which affects network performance. In this paper we describe a method for minimizing network monitoring overhead based on shortest path tree (SPT) protocol. We describe two different variations of the problem: the A-problem and the E-problem, and show that there is a significant difference between...
Supporting multicast applications has drawn increased attention in the development of WDM based optical networks. To provide a high level of availability in the face of node or link failure for multicast traffic, pre-assigned spare capacity in the networks is needed. This paper studies the problem of constructing a minimum-cost, two-connected subgraph, satisfying the wavelength conversion constraint,...
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