Noisy fitness evaluation in genetic algorithms and the dynamics of learning

A theoretical model is presented which describes selection in a genetic algorithm (GA) under a stochastic fitness measure and correctly accounts for finite population effects. Although this model describes a number of selection schemes, we only consider Boltzmann selection in detail here as results for this form of selection are particularly transparent when fitness is corrupted by additive Gaussian noise. Finite population effects are shown to be of fundamental importance in this case, as the noise has no effect in the infinite population limit. In the limit of weak selection we show how the effects of any Gaussian noise can be removed by increasing the population size appropriately. The theory is tested on two closely related problems: the one-max problem corrupted by Gaussian noise and generalization in a perceptron with binary weights. The averaged dynamics can be accurately modelled for both problems using a formalism which describes the dynamics of the GA using methods from statistical mechanics. The second problem is a simple example of a learning problem and by considering this problem we show how the accurate characterization of noise in the fitness evaluation may be relevant in machine learning. The training error (negative fitness) is the number of misclassified training examples in a batch and can be considered as a noisy version of the generalization error if an independent batch is used for each evaluation. The noise is due to the finite batch size and in the limit of large problem size and weak selection we show how the effect of this noise can be removed by increasing the population size. This allows the optimal batch size to be determined, which minimizes computation time as well as the total number of training examples required.

Fitness and novelty in evolutionary art

In this paper the effects of introducing novelty search in evolutionary art are explored. Our algorithm combines fitness and novelty metrics to frame image evolution as a multi-objective optimisation problem, promoting the creation of images that are both suitable and diverse. The method is illustrated by using two evolutionary art engines for the evolution of figurative objects and context free design grammars. The results demonstrate the ability of the algorithm to obtain a larger set of fit images compared to traditional fitness-based evolution, regardless of the engine used.

DNA Simulation of Genetic Algorithms: Fitness Computation

* This work has been partially supported by Spanish Project TIC2003-9319-c03-03 “Neural Networks and Networks of Evolutionary Processors”.

Survey of General Optical Council disciplinary and fitness to practise hearings:2001-2011

The aim of this survey was to review 187 transcripts from the United Kingdom’s General Optical Council (GOC) Disciplinary and Fitness To Practise (FTP) Committee hearings from 2001 to 2011 in order to identify common themes and thereby help practitioners to avoid the more frequently occurring pitfalls that were recorded during this period. The study covered changes in GOC FTP regulations in 2005, which involved a change from a disciplinary to a fitness to practise process. The number of cases was very small compared to the total number of optometrist and dispensing optician registrants, which was 13709 in 2001-02 rising to 18582 in 2010-11. The main findings indicated that between 2001 and 2011 there was a three times greater likelihood that male registrants versus female registrants would be brought in front of a GOC Disciplinary or FTP Committee. In terms of erasures from the GOC registers between 2001 and 2011, male registrants were also more likely to be erased than females. The male: female split for erasures between 2001 and 2011 was five: one, increasing to seven: one when considering the situation post the 2005 GOC FTP rule change. Of the cases brought before the Disciplinary and FTP Committees between 2001 and 2011, it was noted that cases implicating theft and fraud were most frequent representing 27% of hearings examined (17% involving NHS fraud and 10% theft or fraud from an employer). The examination of transcripts revealed other hearings were more complex. These hearings often had a primary reason for the investigation that highlighted further secondary concerns that also required investigation.

A fittség (m)értéke. A fizikai inaktivitás nemzetgazdasági terhei Magyarországon (The value (degree) of fitness. The national economic costs of physical inactivity in Hungary)

Az elmúlt években Magyarországon is fokozatosan nőtt az érdeklődés az életminőség vizsgálata iránt. A 2004-2006 közötti időszakra készült első Nemzeti Fejlesztési Terv fő célkitűzése a lakosság életminőségének javítása volt, de célját nem érte el, mivel a WHO 2010 májusában közzétett statisztikája szerint a magyarországi életminőség-mutatók az európai rangsor végén találhatók. Elszomorító az Eurobarométer 2010. évi reprezentatív kutatásának eredménye: a népesség 77 százalékának életmódja mozgásszegény, fizikailag inaktív. Kutatásunk során azt a ténylegesen hiánypótló célt kívántuk elérni, hogy meghatározzuk és számszerűsítsük a mozgásszegény életmódból adódó nemzetgazdasági terheket, valamint megbecsüljük a fizikai inaktivitás csökkentésével elérhető megtakarítások számszerűsíthető mértékét. Az Országos Egészségbiztosítási Pénztár (OEP) és egy saját országos kérdőíves kutatás (n = 1158) adataira támaszkodtunk. A fizikai inaktivitás betegségeire vonatkozó megtakarítási lehetőségeket tételesen határoztuk meg, majd megállapítottuk az inaktivitásból származó gazdasági terheket, aminek alapján a döntéshozók elkészíthetik a fizikai inaktivitás csökkentésre alkalmas akcióterveiket. Ezzel nemcsak a lakosság "közérzete" javulhat számottevően, de komolyabb költségeket is meg lehet takarítani közép- és hosszú távon. / === / Interest in examining the quality of life has increased steadily in Hungary in recent years. Improving it was the main objective of the first National Development Plan, for the 2004-6 period, but it failed to do so, for Hungary's indices for quality of life were at the bottom of the European list according to figures published by the WHO in May 2010. The results of the representative research Furobarometer 2010 are saddening: 77 per cent of the population pursue a low-exercise, physically inactive lifestyle. The authors' researches sought to fill a gap by measuring and quantifying the national economic costs of a low-exercise lifestyle and to estimate quantitatively the savings to be made by reducing such physical inactivity. The paper relics on the data of the National Health Insurance Fund and on an authors' questionnaire (n = 1158). The potential savings on illness relating to physical activity are listed one by one. to arrive at the economic costs of such inactivity, based on which it is possible for decision-makers to prepare adequate action plans for reducing physical inactivity. This will improve the "morale" of the public and bring appreciable savings in the medium and long term.

Student perceptions of the school physical fitness testing program: The Fitnessgram

The purpose of this study was to determine fifth grade students' perceptions of the Fitnessgram physical fitness testing program. This study examined if the Fitnessgram physical fitness testing experience promotes an understanding of the health-related fitness components and examined the relationship between individual fitness test scores and time spent participating in out-of-school physical activity. Lastly, students' thoughts and feelings concerning the Fitnessgram experience were examined. ^ The primary participant population for the study was 110 fifth grade students at Redland Elementary School, a Miami-Dade County Public School (M-DCPS). Data were collected over the course of 5 months. Multiple sources of data allowed for triangulation. Data sources included Fitnessgram test scores, questionnaires, document analysis, and in-depth interviews. ^ Interview data were analyzed qualitatively for common broad themes, which were identified and defined. Document analysis included analyzing student fitness test scores and student questionnaire data. This information was analyzed to determine if the Fitnessgram test scores have an impact on student views about the school fitness-testing program. Data were statistically analyzed using analysis of frequency, crosstabulations (Bryman & Duncan, 1997), and Somers'd Correlation (Bryman & Duncan, 1997). The results of the analysis of data on student knowledge of the physical fitness components tested by each Fitnessgram test revealed students do not understand the health-related fitness components. ^ The results of determining a relationship between individuals' fitness test scores and time spent in out-of-school physical activity revealed a significant positive relationship for 2 of the 6 Fitnessgram tests. ^ The results of examining students' thoughts and feelings about each Fitnessgram test focused around 2 broad themes: (a) these children do not mind the physical fitness testing and (b) how they felt about the experience was directly related to how they thought they had performed. ^ If the goal of physical fitness was only to get children fit, this test may be appropriate. However, the ultimate goal of physical fitness is to encourage students to live active and healthy lifestyles. Findings suggest the Fitnessgram as implemented by M-DCPS may not be the most suitable measurement instrument when assessing attitudinal changes that affect a healthy lifelong lifestyle. ^

A Geographic Perspective of Cuban Landscapes

Beginning in the era of the Spanish conquest and taking the reader right up to the present day, this book focuses on how the landscape of Cuba has changed and evolved into the environment we see today. It illustrates the range of factors – economic, political and cultural – that have determined Cuba’s physical geography, and explores the shifting conservation measures which have been instituted in response to new methods in agriculture and land management. The text uses historical documents, fieldwork, Geographic Information System (GIS) data and remotely-sensed satellite imagery to detail Cuba’s extensive land-use history as well as its potential future. The author goes further to analyze the manner, speed and methods of landscape change, and examines the historical context and governing agendas that have had an impact on the relationship between Cuba’s inhabitants and their island. Gebelein also assesses the key role played by agricultural production in the framework of international trade required to sustain Cuba’s people and its economy. The book concludes with a review of current efforts by Cuban and other research scientists, as well as private investors, conservation managers and university professors who are involved in shaping Cuba’s evolving landscape and managing it during the country’s possible transition to a more politically diverse, enfranchised and open polity.

Chilling damage in a changing climate in coastal landscapes of the subtropical zone: a case study from south Florida

Extensive portions of the southern Everglades are characterized by series of elongated, raised peat ridges and tree islands oriented parallel to the predominant flow direction, separated by intervening sloughs. Tall herbs or woody species are associated with higher elevations and shorter emergent or floating species are associated with lower elevations. The organic soils in this “Ridge-and-Slough” landscape have been stable over millennia in many locations, but degrade over decades under altered hydrologic conditions. We examined soil, pore water, and leaf phosphorus (P) and nitrogen (N) distributions in six Ridge and Slough communities in Shark Slough, Everglades National Park. We found P enrichment to increase and N to decrease monotonically along a gradient from the most persistently flooded sloughs to rarely flooded ridge environments, with the most dramatic change associated with the transition from marsh to forest. Leaf N:P ratios indicated that the marsh communities were strongly P-limited, while data from several forest types suggested either N-limitation or co-limitation by N and P. Ground water stage in forests exhibited a daytime decrease and partial nighttime recovery during periods of surface exposure. The recovery phase suggested re-supply from adjacent flooded marshes or the underlying aquifer, and a strong hydrologic connection between ridge and slough. We therefore developed a simple steady-state model to explore a mechanism by which a phosphorus conveyor belt driven by both evapotranspiration and the regional flow gradient can contribute to the characteristic Ridge and Slough pattern. The model demonstrated that evapotranspiration sinks at higher elevations can draw in low concentration marsh waters, raising local soil and water P concentrations. Focusing of flow and nutrients at the evapotranspiration zone is not strong enough to overcome the regional gradient entirely, allowing the nutrient to spread downstream and creating an elongated concentration plume in the direction of flow. Our analyses suggest that autogenic processes involving the effects of initially small differences in topography, via their interactions with hydrology and nutrient availability, can produce persistent physiographic patterns in the organic sediments of the Everglades.

Chilling damage in a changing climate in coastal landscapes of the subtropical zone: a case study from south Florida

Freeze events significantly influence landscape structure and community composition along subtropical coastlines. This is particularly true in south Florida, where such disturbances have historically contributed to patch diversity within the mangrove forest, and have played a part in limiting its inland transgression. With projected increases in mean global temperatures, such instances are likely to become much less frequent in the region, contributing to a reduction in heterogeneity within the mangrove forest itself. To understand the process more clearly, we explored the dynamics of a Dwarf mangrove forest following two chilling events that produced freeze-like symptoms, i.e., leaf browning, desiccation, and mortality, and interpreted the resulting changes within the context of current winter temperatures and projected future scenarios. Structural effects from a 1996 chilling event were dramatic, with mortality and tissue damage concentrated among individuals comprising the Dwarf forest's low canopy. This disturbance promoted understory plant development and provided an opportunity for Laguncularia racemosa to share dominance with Rhizophora mangle. Mortality due to the less severe 2001 event was greatest in the understory, probably because recovery of the protective canopy following the earlier freeze was still incomplete. Stand dynamics were static over the same period in nearby unimpacted sites. The probability of reaching temperatures as low as those recorded at a nearby meteorological station (≤3 °C) under several warming scenarios was simulated by applying 1° incremental temperature increases to a model developed from a 42-year temperature record. According to the model, the frequency of similar chilling events decreased from once every 1.9 years at present to once every 3.4 and 32.5 years with 1 and 4 °C warming, respectively. The large decrease in the frequency of these events would eliminate an important mechanism that maintains Dwarf forest structure, and promotes compositional diversity.

Across-scale patterning of plant-soil-water interactions surrounding tree islands in Southern Everglades landscapes

The freshwater Everglades is a complex system containing thousands of tree islands embedded within a marsh-grassland matrix. The tree island-marsh mosaic is shaped and maintained by hydrologic, edaphic and biological mechanisms that interact across multiple scales. Preserving tree islands requires a more integrated understanding of how scale-dependent phenomena interact in the larger freshwater system. The hierarchical patch dynamics paradigm provides a conceptual framework for exploring multi-scale interactions within complex systems. We used a three-tiered approach to examine the spatial variability and patterning of nutrients in relation to site parameters within and between two hydrologically defined Everglades landscapes: the freshwater Marl Prairie and the Ridge and Slough. Results were scale-dependent and complexly interrelated. Total carbon and nitrogen patterning were correlated with organic matter accumulation, driven by hydrologic conditions at the system scale. Total and bioavailable phosphorus were most strongly related to woody plant patterning within landscapes, and were found to be 3 to 11 times more concentrated in tree island soils compared to surrounding marshes. Below canopy resource islands in the slough were elongated in a downstream direction, indicating soil resource directional drift. Combined multi-scale results suggest that hydrology plays a significant role in landscape patterning and also the development and maintenance of tree islands. Once developed, tree islands appear to exert influence over the spatial distribution of nutrients, which can reciprocally affect other ecological processes.