Optimizing One Million Variable NK Landscapes by Hybridizing Deterministic Recombination and Local Search

In gray-box optimization, the search algorithms have access to the variable interaction graph (VIG) of the optimization problem. For Mk Landscapes (and NK Landscapes) we can use the VIG to identify an improving solution in the Hamming neighborhood in constant time. In addition, using the VIG, deterministic Partition Crossover is able to explore an exponential number of solutions in a time that is linear in the size of the problem. Both methods have been used in isolation in previous search algorithms. We present two new gray-box algorithms that combine Partition Crossover with highly efficient local search. The best algorithms are able to locate the global optimum on Adjacent NK Landscape instances with one million variables. The algorithms are compared with a state-of-the-art algorithm for pseudo-Boolean optimization: Gray-Box Parameterless Population Pyramid. The results show that the best algorithm is always one combining Partition Crossover and highly efficient local search. But the results also illustrate that the best optimizer differs on Adjacent and Random NK Landscapes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Enhancing partition crossover with articulation points analysis

Partition Crossover is a recombination operator for pseudo-Boolean optimization with the ability to explore an exponential number of solutions in linear or square time. It decomposes the objective function as a sum of subfunctions, each one depending on a different set of variables. The decomposition makes it possible to select the best parent for each subfunction independently, and the operator provides the best out of $2^q$ solutions, where $q$ is the number of subfunctions in the decomposition. These subfunctions are defined over the connected components of the recombination graph: a subgraph of the objective function variable interaction graph containing only the differing variables in the two parents. In this paper, we advance further and propose a new way to increase the number of linearly independent subfunctions by analyzing the articulation points of the recombination graph. These points correspond to variables that, once flipped, increase the number of connected components. The presence of a connected component with an articulation point increases the number of explored solutions by a factor of, at least, 4. We evaluate the new operator using Iterated Local Search combined with Partition Crossover to solve NK Landscapes and MAX-SAT.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Funding was provided by the Fulbright program, the Spanish Ministry of Education, Culture and Sport (CAS12/00274), the Spanish Ministry of Economy and Competitiveness and FEDER (TIN2014-57341-R and TIN2017-88213-R), the Air Force Office of Scientific Research, (FA9550-11-1-0088), the Leverhulme Trust (RPG-2015-395), the FAPESP (2015/06462-1) and CNPq (304400/2014-9)

On finite-size effects in computer simulations using the Ewald potential

We discuss the origin and relevance for computer simulations of a strong finite-size effect that appears when using the Ewald summation formula. It can be understood as arising from a volume-dependent shift of the potential in a finite, periodic box relative to the infinite volume limit. This shift is due to the fact that the ``zero of energy'' for a periodic system cannot be defined by letting the interacting particles be separated by an infinite distance; the correct definition corresponds to setting its \bbox k=\bbox 0 Fourier mode to zero. The implications of this effect for computer simulations are discussed.Comment: Submitted to Journal of Chemical Physic

Categorías de uso de las gráficas en ingeniería

Los modelos empleados en la didáctica de la matemática han estado fuertemente anclados al predominio de epistemologías de conceptos matemáticos, dejando a un lado el hecho que la matemática está al servicio de otros dominios científicos y de otras prácticas de referencia (Cordero, 2006). Lo cual nos ha llevado a realizar una investigación que busca ubicar los marcos de referencia donde el conocimiento matemático adquiera sentido y significación (Cantoral y Farfán, 2003). Para ello realizamos un estudio de los usos de las gráficas en Ingeniería, de manera particular en mecánica de fluidos

The dependence of halo bias on age, concentration and spin

Halo bias is the main link between the matter distribution and dark matter halos. In its simplest form, halo bias is determined by halo mass, but there are known additional dependencies on other halo properties which are of consequence for accurate modeling of galaxy clustering. Here we present the most precise measurement of these secondary-bias dependencies on halo age, concentration, and spin, for a wide range of halo masses spanning from 10$^{10.7}$ to 10$^{14.7}$ $h^{-1}$ M$_{\odot}$. At the high-mass end, we find no strong evidence of assembly bias for masses above M$_{vir}$ $\sim10^{14}$ $h^{-1}$ M$_{\odot}$. Secondary bias exists, however, for halo concentration and spin, up to cluster-size halos, in agreement with previous findings. For halo spin, we report, for the first time, two different regimes: above M$_{vir}\sim$10$^{11.5}$ $h^{-1}$ M$_{\odot}$, halos with larger values of spin have larger bias, at fixed mass, with the effect reaching almost a factor 2. This trend reverses below this characteristic mass. In addition to these results, we test, for the first time, the performance of a multi-tracer method for the determination of the relative bias between different subsets of halos. We show that this method increases significantly the signal-to-noise of the secondary-bias measurement as compared to a traditional approach. This analysis serves as the basis for follow-up applications of our multi-tracer method to real data.Comment: 11 pages, 6 figures, submitted to MNRA

Dipteran chromosomes: a simple method for obtaining high quality chromosomal preparations

For cytogenetic studies it is necessary to develop an efficient method of chromosome preparation with wellpreserved and dispersed chromosomes and little or no cell-wall debris. In this study, we describe a method for obtaining high quality chromosomal preparations of dipteran cells. This procedure combines drop method and air-dry technique and produces a cell suspension with separated and mixed cells. Suspended mitotic cells were then dropped onto a glass slide in order to distribute the cytoplasm and spread the chromosomes. We compare and evaluate different chromosome preparation methods to develop a more reliable procedure for the resolution of chromosome characteristics and chromosome bandings in blow fly mitotic chromosomes. The combined drop and air-dry technique described here is convenient for identification of sex chromosomes. Using this protocol, acceptable high-quality chromosomal spreads with flattened cells and no cell debris, and without damage and/or loss of chromosomes were obtained.Fil: Chirino, Monica Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Laboratorio de Biología Cromosómica; ArgentinaFil: Rossi, Luis Francisco. Universidad de Buenos Aires. Facultad de Medicina. Laboratorio de Biología Cromosómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bressa, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Luaces, Juan Pablo. Universidad de Buenos Aires. Facultad de Medicina. Laboratorio de Biología Cromosómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Merani, Maria Susana. Universidad de Buenos Aires. Facultad de Medicina. Laboratorio de Biología Cromosómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Editorial for the Special Issue on Combinatorial Optimization Problems

First paragraph: In combinatorial optimization, the goal is to find an optimal solution, according to some objective function, from a discrete search space. These problems arise widely in industry and academia and, unfortunately, many of them are NP-hard and no polynomial time algorithm can guarantee their solution to a certified optimality unless. Therefore, in the last decades researchers have investigated the use of stochastic search algorithms to find near optimal solutions to these problems. In particular, great research efforts have been devoted to the development and application of metaheuristic algorithms to solve combinatorial optimization problems

Use of m-Health Technology for Preventive Interventions to Tackle Cardiometabolic Conditions and Other Non-Communicable Diseases in Latin America- Challenges and Opportunities

In Latin America, cardiovascular disease (CVD) mortality rates will increase by an estimated 145% from 1990 to 2020. Several challenges related to social strains, inadequate public health infrastructure, and underfinanced healthcare systems make cardiometabolic conditions and non-communicable diseases (NCDs) difficult to prevent and control. On the other hand, the region has high mobile phone coverage, making mobile health (mHealth) particularly attractive to complement and improve strategies toward prevention and control of these conditions in low- and middle-income countries. In this article, we describe the experiences of three Centers of Excellence for prevention and control of NCDs sponsored by the National Heart, Lung, and Blood Institute with mHealth interventions to address cardiometabolic conditions and other NCDs in Argentina, Guatemala, and Peru. The nine studies described involved the design and implementation of complex interventions targeting providers, patients and the public. The rationale, design of the interventions, and evaluation of processes and outcomes of each of these studies are described, together with barriers and enabling factors associated with their implementation.Fil: Beratarrechea, Andrea Gabriela. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Diez Canseco, Francisco. Universidad Peruana Cayetano Heredia; PerúFil: Irazola, Vilma. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Miranda, Jaime. Universidad Peruana Cayetano Heredia; PerúFil: Ramirez Zea, Manuel. Institute of Nutrition of Central America and Panama; GuatemalaFil: Rubinstein, Adolfo Luis. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin