Cutting plane methods are widely used for solving convex optimization problems and are of fundamental importance, e.g., to provide tight bounds for Mixed-Integer Programs (MIPs). this is obtained by embedding a cut-se...
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ISBN:
(纸本)9783642135194
Cutting plane methods are widely used for solving convex optimization problems and are of fundamental importance, e.g., to provide tight bounds for Mixed-Integer Programs (MIPs). this is obtained by embedding a cut-separation module within a search scheme. the importance of a sound search scheme is well known in the Constraint programming (CP) community. Unfortunately, the "standard" search scheme typically used for MIP problems, known as the Kelley method, is often quite unsatisfactory because of saturation issues. In this paper we address the so-called Lift-and-Project closure for 0-1 MIPs associated with all disjunctive cuts generated from a given set of elementary disjunction. We focus on the search scheme embedding the generated cuts. In particular, we analyze a general meta-scheme for cutting plane algorithms, called in-out search, that was recently proposed by Ben-Ameur and Neto [1]. Computational results on test instances from the literature are presented, showing that using a more clever meta-scheme on top of a black-box cut generator may lead to a significant improvement.
Recently the electronic structure and magnetism of the "111" type LiFeAs superconductor has been investigated by first principles calculations based on the density functionaltheory. It is concluded that the...
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Recently the electronic structure and magnetism of the "111" type LiFeAs superconductor has been investigated by first principles calculations based on the density functionaltheory. It is concluded that the system has a metallic striped anti-ferromagnetic ground state with a very small magnetic moment. Moreover, the effect of electronic correlation effect is also found to be weak. this finding is consistent with recent experiments and calculations on similar compounds. A strong covalent interaction has been suggested as a reason for the weak electron correlation. In this paper, the Fe As and Fe Fe interactions are examined from the analysis of the electronic localization function (ELF). Surprisingly, no strong evidence supporting Fe As and Fe Fe covalent bonding is found. A more delocalized electron distribution is observed in the Fe layers. therefore, the Fe 3d electrons are not as localized in the oxides and therefore the electron correlation effect is small. this is a plausible explanation for the apparent success of the local density approximation (LSDA) describing the weak magnetism in LiFeAs.
Seahawk is a browser for Moby Web services, which are online tools using a shared semantic registry and data formats. To make a wider array of tools available within Seahawk, the Daggoo system helps users adapt forms ...
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ISBN:
(纸本)9783642151194
Seahawk is a browser for Moby Web services, which are online tools using a shared semantic registry and data formats. To make a wider array of tools available within Seahawk, the Daggoo system helps users adapt forms on existing Web sites to Moby's specifications. Biologists were interviewed and given workflow design tasks, which revealed the types of tools present in their conceptual analysis workflows, and the types of control flow they understood. these observations were used to enhance Seahawk so that Moby and external Web tools can be browsed to create workflows "by demonstration". A flow-up user study measured how effectively biologists could 1) demonstrate a workflow for a realistic task, 2) understand the automatically generated workflow, and 3) use the workflow in the Taverna workflow editor/enactor. the results show promise that biologists without programming experience can become self-sufficient in analysis automation, using workflow-by-demonstration as a first step.
We propose a hybrid approach for solving the resource-constrained project scheduling problem which is an extremely hard to solve combinatorial optimization problem of practical relevance. Jobs have to be scheduled on ...
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ISBN:
(纸本)9783642135194
We propose a hybrid approach for solving the resource-constrained project scheduling problem which is an extremely hard to solve combinatorial optimization problem of practical relevance. Jobs have to be scheduled on (renewable) resources subject to precedence constraints such that the resource capacities are never exceeded and the latest completion time of all jobs is minimized. the problem has challenged researchers from different communities, such as integer programming (IP), constraint programming (CP), and satisfiability testing (SAT). Still, there are instances with 60 jobs which have not been solved for many years. the currently best known approach, LAZYFD, is a hybrid between CP and SAT techniques. In this paper we propose an even stronger hybridization by integrating all the three areas, IP, CP, and SAT, into a single branch-and-bound scheme. We show that lower bounds from the linear relaxation of the IP formulation and conflict analysis are key ingredients for pruning the search tree. First computational experiments show very promising results. For five instances of the well-known PSPLIB we report an improvement of lower bounds. Our implementation is generic, thus it can be potentially applied to similar problems as well.
Memoization is a well-known technique for improving the performance of a program, but it has been confined mostly to functionalprogramming, where no mutable state or side-effects exist. Most object-oriented programs,...
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the development of embedded sensing applications based on integrated circuits leads to ever-growing complexity of VHDL-code and requires sophisticated testability to achieve high diagnostic coverage. the norm IEC 6150...
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the Global Arrays toolkit is a library that allows programmers to write parallel programs that use large arrays distributed across processing nodes through the Aggregate Remote Memory Copy Interface (ARMCI). OpenMP is...
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ISBN:
(纸本)9789746724913
the Global Arrays toolkit is a library that allows programmers to write parallel programs that use large arrays distributed across processing nodes through the Aggregate Remote Memory Copy Interface (ARMCI). OpenMP is an application programming interface that supports shared memory multiprocessing on many architectures and platforms. In the Symmetric-Multi Processors (SMP), the Global Arrays toolkit will expose the programmers quite similar to that provided by OpenMP. In this study, we will further our investigation on the performance of a parallel application implemented withthe Global Arrays toolkit and OpenMP on Grid computing environment. the investigation focuses on the case that an SMP cluster is included in the Grid computing environment. the multi-level parallelism together with multi-level topology-aware techniques have been used in both implementations. We have found that performance of the evaluating application implemented with Global Arrays technique is comparable to that of the application implemented with OpenMP. this implies that programmer can directly port the Global Arrays application directly to the SMP cluster yet its performance is not dropped compared to the native implementation.
the objective of this paper is to determine the 24-hour unit commitment with minimum total generation cost subjecting to power flow constraints in both normal operating state and contingency state, which is considered...
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ISBN:
(纸本)9789746724913
the objective of this paper is to determine the 24-hour unit commitment with minimum total generation cost subjecting to power flow constraints in both normal operating state and contingency state, which is considered the security-constrained unit commitment (SCUC). In this paper, the Benders' Decomposition technique has been applied by decomposing the problem into two parts: the master problem;and the sub-problems. the master problem which is the unit commitment problem contains integer variables as the on-off status of the generating units, and therefore could be solved as Mixed-Integer programming problem. the branch-and-cut method has been chosen to solve the master mixed-integer problem. there are two subproblems considered in this research: the power flow mismatch equations;and the operating limits of power systems. If the conditions in any subproblems are violated, the Benders Cuts corresponding to the violated constraints are added to the master problem and the mixed-integer unit commitment problem could be resolved. the proposed algorithm is tested on the IEEE 57-bus system with7thermal generating units. the 24-hour load data is made available along withthe additional data for generating units. the results of typical unit commitment, security-constrained unit commitment under normal operating states and SCUC with contingency states are compared. the results show that the total generating costs of SCUC with contingency are higher than the others. However the committed units of that SCUC ensure that the system could still serve load when contingency occurs.
the Message Passing Interface (MPI) is one of the most widely used programming models for parallel computing. However, the amount of memory available to an MPI process is limited by the amount of local memory within a...
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ISBN:
(纸本)9781450300445
the Message Passing Interface (MPI) is one of the most widely used programming models for parallel computing. However, the amount of memory available to an MPI process is limited by the amount of local memory within a compute node. Partitioned Global Address Space (PGAS) models such as Unified Parallel C (UPC) are growing in popularity because of their ability to provide a shared global address space that spans the memories of multiple compute nodes. However, taking advantage of UPC can require a large recoding effort for existing parallel applications. In this paper, we explore a new hybrid parallel programming model that combines MPI and UPC. this model allows MPI programmers incremental access to a greater amount of memory, enabling memory-constrained MPI codes to process larger data sets. In addition, the hybrid model offers UPC programmers an opportunity to create static UPC groups that are connected overMPI. As we demonstrate, the use of such groups can significantly improve the scalability of locality-constrained UPC codes. this paper presents a detailed description of the hybrid model and demonstrates its effectiveness in two applications: a random access benchmark and the Barnes-Hut cosmological simulation. Experimental results indicate that the hybrid model can greatly enhance performance;using hybrid UPC groups that span two cluster nodes, RA performance increases by a factor of 1.33 and using groups that span four cluster nodes, Barnes-Hut experiences a twofold speedup at the expense of a 2% increase in code size.
作者:
Lan XuBusiness School
East China University of Science and Technology Shanghai China
this paper sets up a Malmquist Productivity Index system of economic growth to study the comprehensive capacities and important economic indicators for the 16 cities in the Yangtze River Delta Region. In the progress,...
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this paper sets up a Malmquist Productivity Index system of economic growth to study the comprehensive capacities and important economic indicators for the 16 cities in the Yangtze River Delta Region. In the progress, it makes use of the Two-Stage Linear programming techniques to estimate the distance functions in reflection of the regional economic frontier. Further, the paper analyzes productivity growth because of the scale effect and technical progress which cause the internal differences to move on the different levels. the paper concludes to provide strategic suggestions withthe collaborations, mutual activities, and functional division for each city in the delta region.
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