LP Programs Research Articles

Linear Programs with Conjunctive Database Queries

In this paper, we study the problem of optimizing a linear program whose variables are the answers to a conjunctive query. For this we propose the language LP(CQ) for specifying linear programs whose constraints and objective functions depend on the answer sets of conjunctive queries. We contribute an efficient algorithm for solving programs in a fragment of LP(CQ). The natural approach constructs a linear program having as many variables as there are elements in the answer set of the queries. Our approach constructs a linear program having the same optimal value but fewer variables. This is done by exploiting the structure of the conjunctive queries using generalized hypertree decompositions of small width to factorize elements of the answer set together. We illustrate the various applications of LP(CQ) programs on three examples: optimizing deliveries of resources, minimizing noise for differential privacy, and computing the s-measure of patterns in graphs as needed for data mining.

Vrednost programa lojalnosti - daj mi više ili me tretiraj bolje?

Customer loyalty programs are frequently used by companies to establish and improve relationships with customers by providing them with rewards. Loyalty programs investigated in the literature focus mainly on tangible rewards and economic benefits offered to the customers. However, some research done on intangible rewards of loyalty programs suggest that they can be superior to tangible benefits in affecting customer loyalty. Previous research drew conclusions in industry-specific settings. The aim of the paper is to assess the impact of tangible and intangible benefits on customer loyalty using an on-line customer panel representing different industries. The data collected from over 300 customers is subjected to CFA/SEM analysis in R environment. The main contribution of the present study is that it represents the first attempt (to the best of authors" knowledge) to capture loyalty programs" tangible and intangible value in an Arab cultural context, given the fact the focus was on the participants from the United Arab Emirates. Several important dimensions of LP programs in an Arab country are revealed. Firstly, the study confirmed that social value of a loyalty program significantly impacts customer loyalty. In addition, it was confirmed that the flexibility of a loyalty program increased customer loyalty. Ultimately, it was established that customers value intangible benefits more than the tangible ones.

Optimize the Transport Cost and Environmental Impact of Whey Collection: A Case Study in the Region Trentino A. A. (Italy)

The scope of this research is to elaborate a strategy to minimize the logistic cost of the whey collection. The problem consists of the description of the whey collection basin and transport from CP (Cheese plant) to WPP (Whey processing plant). We started with an initial basic solution and proceeded with successive iterations to find the final optimal solution. Two numeric methods are proposed to solve iteratively the problem: the first one emulates the simplex method, the second one is an empirical solution to find the optimal route. Both are solved with an Excel and Google map software and do not require a dedicated LP program for calculus. The results demonstrate that both methods contribute to solve the transport problem and generate valuable information for the achievement of economic and environmental targets.

The Big Data Newsvendor: Practical Insights from Machine Learning

We investigate the data-driven newsvendor problem when one has n observations of p features related to the demand as well as historical demand data. We propose two approaches to finding the optimal order quantity in this new setting -- Machine Learning (ML) with and without regularization, and Kernel-weights Optimization (KO). We show that the resulting Big Data newsvendor problem can be solved by LP, MIP or QCQP programs under the ML approach, and by a simple sorting algorithm under the KO approach. We justify the use of feature information by showing that not including them yields inconsistent decisions, which translates to sub-optimal costs even with infinite amount of demand data. We then derive finite-sample performance bounds on the out-of-sample costs of the feature-based decisions, which shows (i) the Big Data regime, when over-fitting dominates finite-sample bias, is defined by p > O(n^{-1/(2 8/p)}\sqrt{\log{(n)}}), and (ii) both regularized ML and KO are effective methods to handle over-fitting. Finally, we apply the feature-based algorithms for nurse staffing in a hospital emergency room using a data set from a large UK teaching hospital and find that (i) the best KO and ML algorithms beat the best practice benchmark by 23% and 24% respectively in the out-of-sample cost with statistical significance at the 5% level, and (ii) the best KO algorithm is faster than the best ML algorithm by three orders of magnitude and the best practice benchmark by two orders of magnitude.

A New Approach for Corrective and Preventive Control to Unsolvable Case in Power Networks having DERs

Recently, Korean system operating conditions have gradually approached an upper limit. When a contingency occurs, the power system may have no solutions. Different from the cases of bad initial guesses or the solutions are too close to the solvability boundary in which numerical methods can be applied, for unsolvable cases, the only way to restore solvability would be structure modifications. In this paper, a new approach for corrective and preventive control to such cases is proposed in two steps: (i) finding any solution regardless its feasibility; (ii) for the infeasible solution, make it feasible with additional modifications at load buses having Distributed Energy Resources. The test case built based on the peak load profile of 2008 by KEPCO including 1336 buses is analyzed. Since reactive power compensation is optimized to restore solvability, all demands are met, therefore no blackouts happen. The proposed method was integrated in the LP program designed by power21 Corporation.

Implications of High-Frequency Cochlear Dead Regions for Fitting Hearing Aids to Adults With Mild to Moderately Severe Hearing Loss

A cochlear dead region (DR) occurs at a given frequency when there is a loss of normal functioning of inner hair cells tuned to that frequency. It has been suggested that existence of high-frequency DRs has implications for hearing aid fitting, and that the optimal amount of high-frequency gain is reduced for these patients. However, the data supporting this suggestion has been obtained using listeners with severe or profound hearing loss. It is uncertain whether these results would apply for listeners with the mild to moderately severe hearing loss that is more typical of hearing aid users. This investigation used laboratory and field measurements to examine the effects of reduced high-frequency gain in typical hearing aid users with high-frequency DRs compared with matched users without DRs. The study was a double-blinded, nonrandomized intervention design with 18 matched pairs of adult subjects. In each pair, one subject had high-frequency DRs (usually at one or two test frequencies) and the other subject had no DR. Each subject was fitted unilaterally with a hearing aid having two active programs. One program used a National Acoustics Laboratories (NAL) prescription target for average speech (NAL condition). The other program was identical to NAL except for reduced gain in the high frequencies (low-pass [LP] condition). Outcomes included aided speech recognition in quiet and noise measured in the laboratory, ratings of speech understanding in daily life, and final preference for the NAL or LP program. In laboratory testing, speech recognition in quiet was significantly better when using the NAL program. This result was seen for subjects with DRs and without DRs. When listening in noise, speech recognition was significantly better when using the NAL program for subjects without DRs. For subjects with DRs, results were equivalent for the NAL and LP programs. In daily life, the NAL program received significantly higher ratings for speech understanding, and this result was seen for subjects with and without DRs. When asked about their preference for using the NAL or LP program in daily life, subjects did not always choose the program they had rated as giving better speech understanding, but their preference was not associated with having DRs. About one-third of subjects preferred the LP program. The reason most frequently given for preferring the LP program was that the NAL was too loud. Overall, adult hearing aid wearers with mild to moderately severe hearing loss benefitted from high-frequency gain whether or not they had DRs. In laboratory testing, but not in daily life, subjects with DRs tended to obtain less benefit than those without DRs. However, provision of NAL high-frequency gain never resulted in poorer performance in either group. These results suggest that identification of high-frequency DRs at one or two frequencies does not call for any a priori modification of the target hearing aid prescription for listeners with mild to moderately severe hearing loss.

Lightweight compilation of (C)LP to JavaScript

AbstractWe present and evaluate a compiler from Prolog (and extensions) to JavaScript which makes it possible to use (constraint) logic programming to develop the client side of web applications while being compliant with current industry standards. Targeting JavaScript makes (C)LP programs executable in virtually every modern computing device with no additional software requirements from the point of view of the user. In turn, the use of a very high-level language facilitates the development of high-quality, complex software. The compiler is a back end of the Ciao system and supports most of its features, including its module system and its rich language extension mechanism based onpackages. We present an overview of the compilation process and a detailed description of the run-time system, including the support for modular compilation into separate JavaScript code. We demonstrate the maturity of the compiler by testing it with complex code such as a CLP(FD) library written in Prolog with attributed variables. Finally, we validate our proposal by measuring the performance of some LP and CLP(FD) benchmarks running on top of major JavaScript engines.

Interprovider differentiated service interconnection management models in the Internet bandwidth commodity markets

Due to the recent evolution of telecommunications infrastructure and the Internet as a commodity market for bandwidth, Internet Service Providers (ISPs) encounter new issues concerned with bandwidth management for the network interconnection. Bandwidth commodity exchange is considered a new B2B (Business-to-Business) electronic commerce application that brings new market opportunities to carriers and service providers for managing their bandwidth resources. This paper develops market-based bandwidth management optimization models for Differentiated Service (DiffServ) QoS (Quality of Service) networks using an implementation of the bandwidth management agent, BMP (Bandwidth Management Point). We use network economic models to formulate an optimization problem for the interconnection and resource allocation policy of the DiffServ network. We formulate and develop those economic models as optimization problems of LP, NLP, MILP and mixed integer nonlinear programming (MINLP), and discuss the pricing mechanisms and available solution approaches for the implementation of the BMP's resource optimization process. Different opportunity costs are estimated based on the results of a network simulation using traffic flow statistics measured from a recent Internet backbone. We then numerically simulate the behavior of backbone network ISPs to optimize their profits for various demand scenarios.

Specialised branch-and-bound algorithm for transmission network expansion planning

An algorithm is presented that finds the optimal plan long-term transmission for all cases studied, including relatively large and complex networks. The knowledge of optimal plans is becoming more important in the emerging competitive environment, in which the correct economic signals have to be sent to all participants. The paper presents a new specialised branch-and-bound algorithm for transmission network expansion planning. Optimality is obtained at a cost, however: that is the use of a transportation model for representing the transmission network, in this model only the Kirchhoff current law is taken into account (the second law being relaxed). The expansion problem then becomes an integer linear program (ILP) which is solved by the proposed branch-and bound method without any further approximations. To control combinatorial explosion the branch and bound algorithm is specialised using specific knowledge about the problem for both the selection of candidate problems and the selection of the next variable to be used for branching. Special constraints are also used to reduce the gap between the optimal integer solution (ILP program) and the solution obtained by relaxing the integrality constraints (LP program). Tests have been performed with small, medium and large networks available in the literature.

A System for Automatically Generating Documentation for (C)LP Programs

We describe lpdoc, a tool which generates documentation manuals automatically from one or more logic program source files, written in ISO-Prolog, Ciao, and other (C)LP languages. It is particularly useful for documenting library modules, for which it automatically generates a rich description of the module interface. However, it can also be used quite successfully to document full applications. A fundamental advantage of using lpdoc is that it helps maintaining a true correspondence between the program and its documentation, and also identifying precisely to what version of the program a given printed manual corresponds. The quality of the documentation generated can be greatly enhanced by including within the program text assertions (declarations with types, modes, etc.) for the predicates in the program, and machine-readable comments. One of the main novelties of lpdoc is that these assertions and comments are written using the Ciao system assertion language, which is also the language of communication between the compiler and the user and between the components of the compiler. This allows a significant synergy among specification, documentation, optimization, etc. A simple compatibility library allows conventional (C)LP systems to ignore these assertions and comments and treat normally programs documented in this way. The documentation can be generated in many formats including texinfo, dvi, ps, pdf, info, html/css, Unix nroff/man, Windows help, etc., and can include bibliographic citations and images. lpdoc can also generate “man” pages (Unix man page format), nicely formatted plain ascii “readme” files, installation scripts useful when the manuals are included in software distributions, brief descriptions in html/css or info formats suitable for inclusion in on-line indices of manuals, and even complete WWW and info sites containing on-line catalogs of documents and software distributions. The lpdoc manual, all other Ciao system manuals, and parts of this paper are generated by lpdoc.

A System for Automatically Generating Documentation for (C)LP Programs

A System for Automatically Generating Documentation for (C)LP Programs

Preface: Volume 30, Issue 2

This volume contains the Proceedings of International Workshop on Optimization and Implementation of Declarative Programs (WOID′99). The Workshop was held in held in conjunction with the International Conference on Logic Programming ICLP′99 in Las Cruces, New Mexico, USA on the 2nd and 3rd of December, 1999.Overview:The aim of this workshop was to provide a forum where new trends, ideas and developments concerning the optimization and implementation of declarative languages could be discussed. It was especially geared towards bringing researchers from low-level compilation and high-level optimization together. Indeed, compilers and linkers are getting more and more sophisticated and employ more and more high-level optimizations, such as partial evaluation or deforestation. Researchers in high-level optimization and transformation, on the other hand, realise that low-level issues have to be taken into account in order to apply their techniques in practice. So, in this workshop we wanted to provide the possibility for these two areas to meet and accelerate their synergy.Contributions:Out of 11 submissions 8 papers were selected. To ensure a workshop character ample time was reserved for discussion and each paper was assigned a “key listener” from the program committee. This scheme was borrowed from the LOPSTR workshop series, and proved to be successful. The contributions were arranged in 3 sessions, described below.1. Implementation & Low-level OptimizationThe first paper of the session by R. Muth, S. Watterson, and S. Debray, discussed how the information that certain program variables “almost always” have a particular value (as opposed to “always” as in partial evaluation or constant folding) can and should be exploited for optimization. (For various reasons this paper is not present in this volume of ENTCS.) The other two papers of the session presented new ways of efficiently implementing CLP languages and constructs. The paper by N-F. Zhou and S. Kaneko presented an efficient (hybrid) way to compile equality constraints, while the paper by M. Gavanelli and M. Milano showed how to efficiently implement lazy domain evaluation for Constraint Satisfaction Problems.2. AnalysisThe session on analysis comprised two papers. The first one by K. Ueda developed a new linearity analysis for concurrent logic programs, with the aim of achieving compile time garbage collection. The paper by G. Puebla and M. Hermenegildo provided an encompassing and insightful overview of the important issues and problems that arise when analysing and specialising large programs decomposed into modules.3. SpecializationThe first paper of the last session, by F. Fioravanti, A. Pettorossi, and M. Proietti, presented a novel way to specialise (C)LP programs within a given context. This context allows one to describe additional specialisation constraints which are hard (or impossible) to express in earlier approaches. The next paper, by W. Vanhoof and M. Bruynooghe, dicussed how to achieve a binding-time analysis (i.e., figuring out which values and operations are already known or executable at specialisation time) for offline partial evaluation in the context of Mercury programs with modules. Finally, the paper by M. Leuschel and J. Jorgensen (presented by H. Lehmann) gave an overview of a new, fast offline partial evaluation system (called LOGEN), which can handle partially static data structures and many pure and impure features of Prolog.Further information about the workshop can be obtained at: http://www.ecs.soton.ac.uk/~mal/iclp99.woid.html.The Program Committee was composed of:Saumya Debray(University of Arizona)Bart Demoen(University of Leuven)John Gallagher(University of Bristol)Michael Leuschel (Chair)(University of Southampton)Germán Puebla(University of Madrid)Peter Stuckey(University of Melbourne)Neng-Fa Zhou(Kyushu Institute of Technology)I would like to thank the authors for their participation in the workshop and the program committee for their efforts in reviewing the papers. I also want to thank the Managing Editors of the Electronic Notes in Computer Science series, Michael Mislove, Maurice Nivat, and Christos Papadimitriou, for providing the opportunity to publish the proceedings in this series.Michael Leuschel, Guest Editor

Supernode processing of mixed-integer models

This paper discusses processing software for large scale mixed-integer optimization models. The software is part of the Mathematical OPtimization System MOPS [18] which contains algorithms for solving large-scale LP and mixed-integer programs. The processing techniques are implemented in such a way that they can be applied not only initially but also during the branch-and-bound algorithm.

Linear programming formulation of MDPs in countable state space: The multichain case

We present an Linear Programming formulation of MDPs with countable state and action spaces and no unichain assumption. This is an extension of the Hordijk and Kallenberg (1979) formulation in finite state and action spaces. We provide sufficient conditions for both existence of optimal solutions to the primal LP program and absence of duality gap. Then, existence of a (possibly randomized) average optimal policy is also guaranteed. Existence of a stationary average optimal deterministic policy is also investigated.

Smoothing empirical functions by lp programming

We give three models for smoothing empirical functions. The first model is the well known graduating model given by Whittaker [7], the second and the third model are new. New iterative procedures are presented for solving these models. These iterative procedures are based on the equilibrium conditions of l p programming, so our solution procedure for solving Whittaker's model is also new.

A linear programming regulator applied to hydroelectric reservoir level control

For linear dynamical systems with linear state and control constraints the regulator problem can be formulated as a linear programming problem. A regulator, built around a standard LP program and operating in the Open Loop Optimal Feedback (OLOF) fashion, is presented. The LP-OLOF regulator was implemented on a VAX 11/780 computer to control, in real time, a double water tank laboratory process, and the water level of a hydroelectric power station reservoir. The reservoir control experiment showed that even with an assumed simple process model, satisfactory performance was achieved. In particular it was beneficial that the LP-OLOF regulator allows dynamic changes of the water flow bounds corresponding to the number of generators available at different operating conditions, and that the regulator can predict the water level.

Mathematical programming in the Netherlands

Results of an exhaustive survey of mathematical programming in the Netherlands held in 1982 are presented and, where applicable, compared to a survey held in 1976. It appears that the growth rate has levelled off, that about half of the largest one hundred industrial firms in the Netherlands now apply MP and that the users are quite satisfied with LP programs except for input, output and documentation.

Duality for convex functionals: specific cases

Using our recently developed theory of duality for convex integral functionals, dual problems are constructed for linear functional programming and Lp programming.

The Adequacy of the Independence of Markets Assumption in Interregional Competition Models

An important function of agricultural economics is to determine the competitive potential for beginning or expanding production of a commodity in a specified area. This problem is approached through budgeting techniques and/or more sophisticated models such as linear or reactive programming. Many examples using LP or reactive programming algorithms are available. In two recent studies, reactive models were used to examine the market for potatoes and sweet cherries. These studies provided an insight into the relative competitive position among producing areas and among consuming centers. To reach a solution, the competitive assumption of LP or reactive models requires independence of supply functions for producing regions and demand functions for consuming markets. Thus, frequently the demand price for a given commodity in a market is estimated as a function of volume in that market and perhaps time, income or other variables. The resulting equation is used by inserting the mean value of all explanatory variables except volume, resulting in an equation that has price as a function of volume, plus a constant, and is compatible reactive programming.