Conflicting edges spanning trees and NP-Hard subgraph identification problems

2016 - 2017How often do we try to get the best result with the least effort, spend as little time as possible to perform a task or make the most of the resources available in the workplace? In everyday life, the word ”optimize” is therefore often present. In particular, the optimization has as its object the study and the development of quantitative methodologies and tools for the solution of decision problems. This is a discipline born in the military field about 80 years ago. Over the years, it has found application in several sectors such as logistics and production, finance and telecommunications. Currently it has become an indispensable tool for supporting decision-making processes. The problems faced are typically those in which decisions have to be made on the use of resources available in limited quantities in order to respect an assigned set of constraints, maximizing, for example, the benefit obtainable from the use of the resources themselves... [edited by Author]XXX cicl

Polyhedra and algorithms for problems bridging notions of connectivity and independence

I denne avhandlinga interesserer vi oss for å finne delgrafer som svarer til utvalgte modeller for begrepene sammenheng og uavhengighet. I korthet betyr dette stabile (også kalt uavhengige) mengder med gitt kardinalitet, stabile (også kalt konfliktfrie) spenntrær og pardannelser (eller uavhengige kantmengder) som induserer en sammenhengende delgraf. Dette er kombinatoriske strukturer som kan generaliseres til ulike modeller for nettverksdesign innen telekommunikasjon og forsyningsvirksomhet, plassering av anlegg, fylogenetikk, og mange andre applikasjoner innen operasjonsanalyse og optimering. Vi argumenterer for at de valgte strukturene reiser interessante forskningsspørsmål, og vi bidrar med forbedret matematisk forståelse av selve strukturene, samt forbedrede algoritmer for å takle de tilhørende kombinatoriske optimeringsproblemene. Med det mener vi metoder for å identifisere en optimal struktur, forutsatt at elementene som danner dem (hjørner eller kanter i en gitt graf) er tildelt verdier. Forskninga vår omfatter ulike områder innenfor algoritmer, kombinatorikk og optimering. De fleste resultatene omhandler det å finne bedre beskrivelser av de geometriske strukturene (nemlig 0/1-polytoper) som representerer alle mulige løsninger for hvert av problemene. Slike forbedrede beskrivelser oversettes til lineære ulikheter i heltallsprogrammeringsmodeller, noe som igjen gir mer effektive beregningsresultater når man løser referanseinstanser av hvert problem. Vi påpeker gjentatte ganger betydninga av å dele kildekoden til implementasjonen av alle utviklede algoritmer og verktøy når det foreslås nye modeller og løsningsmetoder for heltallsprogrammering og kombinatorisk optimering. Kodearkivene våre inkluderer fullstendige implementasjoner, utformet med effektivitet og modulær design i tankene, og fremmer dermed gjenbruk, videre forskning og nye anvendelser innen forskning og utvikling.We are interested in finding subgraphs that capture selected models of connectivity and independence. In short: fixed cardinality stable (or independent) sets, stable (or conflict-free) spanning trees, and matchings (or independent edge sets) inducing a connected subgraph. These are combinatorial structures that can be generalized to a number of models across network design in telecommunication and utilities, facility location, phylogenetics, among many other application domains of operations research and optimization. We argue that the selected structures raise appealing research questions, and seek to contribute with improved mathematical understanding of the structures themselves, as well as improved algorithms to face the corresponding combinatorial optimization problems. That is, methods to identify an optimal structure, assuming the elements that form them (vertices or edges in a given graph) have a weight. Our research spans different lines within algorithmics, combinatorics and optimization. Most of the results concern finding better descriptions of the geometric structures (namely, 0/1-polytopes) that represent all feasible solutions to each of the problems. Such improved descriptions translate to linear inequalities in integer programming formulations which, in turn, provide stronger computational results when solving benchmark instances of each problem. We repeatedly remark the importance of sharing an open-source implementation of all algorithms and tools developed when proposing new models and solution methods in integer programming and combinatorial optimization. Our code repositories include full implementations, crafted with efficiency and modular design in mind, thus fostering reuse, further research and new applications in research and development.Doktorgradsavhandlin

Solving the Set Covering Problem with Conflicts on Sets: A new parallel GRASP

In this paper, we analyze a new variant of the well-known NP-hard Set Covering Problem, characterized by pairwise conflicts among subsets of items. Two subsets in conflict can belong to a solution provided that a positive penalty is paid. The problem looks for the optimal collection of subsets representing a cover and minimizing the sum of covering and penalty costs. We introduce two integer linear programming formulations and a quadratic one for the problem and provide a parallel GRASP (Greedy Randomized Adaptive Search Procedure) that, during parallel executions of the same basic procedure, shares information among threads. We tailor such a parallel processing to address the specific problem in an innovative way that allows us to prevent redundant computations in different threads, ultimately saving time. To evaluate the performance of our algorithm, we conduct extensive experiments on a large set of new instances obtained by adapting existing instances for the Set Covering Problem. Computational results show that the proposed approach is extremely effective and efficient providing better results than Gurobi (tackling three alternative mathematical formulations of the problem) in less than 1/6 of the computational time

Economic Growth, Innovation, Cultural Diversity. What Are We All Talking About? A Critical Survey of the State-of-the-art

This report constitutes the first deliverable of the project ENGIME – Economic Growth and Innovation in Multicultural Environments, financed by the European Commission – FP5 – Key Action: Improving socio-economic knowledge base. Contract HPSE-CT2001-50007Multiculturalism, Diversity, Economic Growth

Genomic history of Neolithic to Bronze Age Anatolia, Northern Levant, and Southern Caucasus

Here, we report genome-wide data analyses from 110 ancient Near Eastern individuals spanning the Late Neolithic to Late Bronze Age, a period characterized by intense interregional interactions for the Near East. We find that 6th millennium BCE populations of North/Central Anatolia and the Southern Caucasus shared mixed ancestry on a genetic cline that formed during the Neolithic between Western Anatolia and regions in today’s Southern Caucasus/Zagros. During the Late Chalcolithic and/or the Early Bronze Age, more than half of the Northern Levantine gene pool was replaced, while in the rest of Anatolia and the Southern Caucasus, we document genetic continuity with only transient gene flow. Additionally, we reveal a genetically distinct individual within the Late Bronze Age Northern Levant. Overall, our study uncovers multiple scales of population dynamics through time, from extensive admixture during the Neolithic period to long-distance mobility within the globalized societies of the Late Bronze Age. Video Abstrac

Bowdoin College Catalogue and Academic Handbook (2023-2024)

https://digitalcommons.bowdoin.edu/course-catalogues/1321/thumbnail.jp

An archaeogenomic approach to the population history of Southwest Asia and the Aegean from the Neolithic to the Bronze Age

The goal of the present thesis is to synthesize a novel picture of the population history of the Eastern Mediterranean, through the application of high-throughput methods in ancient DNA. Despite the historical significance of this area for the sociocultural and technological innovations leading to farming and, later, the formation of the earliest state societies, comprehensive archaeogenomic approaches to understanding mobility and social traditions have been limited. Here, I undertook the analyses of a large assemblage of human remains from collections and institutions across Europe and Asia, leading to more than 200 genomes in total – the largest number ever reported for the Aegean, Anatolia and the Northern Levant. By applying state-of-the-art methods in ancient DNA and population genetics, I could reach a number of notable observations regarding the scale and timing of mobility and migration and the admixture among populations, whose interactions were previously inferred only through their material culture. In addition, my research uncovered hitherto unknown aspects of the micro-history, and cultural practices related to family and marriage rules, thereby enriching the way we understand the organization and beliefs of these past societies

Population Structure and Frankish Ethnogenesis (AD 400-900)

abstract: The transition from Late Antiquity to Early Medieval Europe (ca. AD 400-900) is often characterized as a period of ethnogenesis for a number of peoples, such as the Franks. Arising during protracted contact with the Roman Empire, the Franks would eventually form an enduring kingdom in Western Europe. However, there is little consensus about the processes by which they formed an ethnic group. This study takes a fresh look at the question of Frankish ethnogenesis by employing a number of theoretical and methodological subdisciplines, including population genetics and ethnogenetic theory. The goals of this work were 1) to validate the continued use of biological data in questions of historical and archaeological significance; and 2) to elucidate how Frankish population structure changed over time. Toward this end, measurements from the human dentition and crania were subjected to rigorous analytical techniques and interpreted within a theoretical framework of ethnogenetic life cycles. Results validate existing interpretations of intra-regional biological continuity over time. However, they also reveal that 1) there are clear biological and geographical differences between communities, and 2) there are hints of diachronic shifts, whereby some communities became more similar to each other over time. These conclusions complement current ethnohistoric work arguing for the increasing struggle of the Frankish kingdom to unify itself when confronted by strong regionally-based politics.Dissertation/ThesisDoctoral Dissertation Anthropology 201