Revisiting Implicit and Explicit Averaging for Noisy Optimization

Explicit and implicit averaging are two well-known strategies for noisy optimization. Both strategies can counteract the disruptive effect of noise; however, a critical question remains: which one is more efficient? This question has been raised in many studies, with conflicting preferences and, in some cases, findings. Nevertheless, theoretical findings on the noisy sphere problem with additive Gaussian noise supports the superiority of implicit averaging, which may have had a strong impact on the preference of implicit averaging in more recent evolutionary methods for noisy optimization. This study speculates that the analytically supported superiority of implicit averaging relies on specific features of the noisy sphere problem with additive noise, which cannot be generalized to other problems. It enumerates these features and designs controlled numerical experiments to investigate this potential reliance. Each experiment gradually suppresses one specific feature, and the progress rate is numerically calculated for different values of the sample size given a fixed evaluation budget. Our empirical results indicate that for a wide range of noise strength and evaluation budget per iteration, the more these specific features are suppressed, the more the optimal averaging strategy deviates from implicit toward explicit averaging, which confirms our speculations. Consequently, the optimal sample size, which is regarded as the tradeoff between implicit and explicit averaging, depends on the problem characteristics and should be learned during optimization for maximum efficiency

Static and Dynamic Multimodal Optimization by Improved Covariance Matrix Self-Adaptation Evolution Strategy with Repelling Subpopulations

The covariance matrix self-adaptation evolution strategy with repelling subpopulations (RS-CMSA-ES) is one of the most successful multimodal optimization (MMO) methods currently available. However, some of its components may become inefficient in certain situations. This study introduces the second variant of this method, called RS-CMSA-ESII. It improves the adaptation schemes for the normalized taboo distances of the archived solutions and the covariance matrix of the subpopulation, the termination criteria for the subpopulations, and the way in which the infeasible solutions are treated. It also improves the time complexity of RS-CMSA-ES by updating the initialization procedure of a subpopulation and developing a more accurate metric for determining critical taboo regions. The effects of these modifications are illustrated by designing controlled numerical simulations. RS-CMSA-ESII is then compared with the most successful and recent niching methods for MMO on a widely adopted test suite. The results obtained reveal the superiority of RS-CMSA-ESII over these methods, including the winners of the competition on niching methods for MMO in previous years. Besides, this study extends RS-CMSA-ESII to dynamic MMO and compares it with a few recently proposed methods on the modified moving peak benchmark functions

PyDDRBG: A Python framework for benchmarking and evaluating static and dynamic multimodal optimization methods

PyDDRBG is a Python framework for generating tunable test problems for static and dynamic multimodal optimization. It allows for quick and simple generation of a set of predefined problems for non-experienced users, as well as highly customized problems for more experienced users. It easily integrates with an arbitrary optimization method. It can calculate the optimization performance when measured according to the robust mean peak ratio. PyDDRBG is expected to advance the fields of static and dynamic multimodal optimization by providing a common platform to facilitate the numerical analysis, evaluation, and comparison in these fields

The architecture of the middle ear in the small Indian mongoose (Herpestes Javanicus)

The small Indian mongoose (Herpestes javanicus) is native to the Middle East, Iran and much of southern Asia. For this study the middle ears of a total of 6 adult small Indian mongooses, both fresh and museum samples were explored by using of dissection and plain radiography. On the one hand, at least in some species of the mongoose vocalisations and hearings play a critical role in coordinating behaviours. On the other hand, the ear region has provided useful character relevant for mammalian phylogeny. So, the aim of the present study is a brief discussion of the various anatomic particularities of the middle ear based on a combination of existing data and the results of the authors’ study in the small Indian mongoose

The effect of seating preferences of the medical students on educational achievement

Background: The seat selection and classroom dynamics may have mutual influence on the student performance and participation in both assigned and random seating arrangement. Purpose: The aim of the study was to understand the influence of seat selection on educational achievement. Methods: The seating positions of the medical students were recorded on an architectural plan during each class session and the means and standard deviations of the students’ locations were calculated in X and Y orientations. The locations of the students in the class were analyzed based on three architectural classifications: interactional zone, distance from the board, and access to the aisles. Final exam scores were used to measure the students’ educational achievement. Results: Our results demonstrate that there is a statistically significant relationship between the student's locations in the class and their attendance and educational achievements. Conclusion: Two factors may effect on educational achievement: student seating in the high interactional zone and minimal changes in seating location. Seating in the high interaction zone was directly associated with higher performance and inversely correlated with the percentage of absences. This observation is consistent with the view that students in the front of the classroom are likely more motivated and interact with the lecturer more than their classmates

The top 100 global water questions: Results of a scoping exercise

YesGlobal water security presents a complex problem for human societies and will become more acute as the impacts of climate change escalate. Water security connects the practical water and sanitation challenges of households to the dynamics of global hydroclimates and ecosystems in the Anthropocene. To ensure the successful deployment of attention and resources, it is necessary to identify the most pressing questions for water research. Here, we present the results of a scoping exercise conducted across the global water sector. More than 400 respondents submitted an excess of 4,000 potential questions. Drawing on expert analysis, we highlight 100 indicative research questions across six thematic domains: water and sanitation for human settlements; water and sanitation safety risk management; water security and scarcity; hydroclimate-ecosystem-Anthropocene dynamics; multi-level governance; and knowledge production. These questions offer an interdisciplinary and multi-scalar framework for guiding the nature and space of water research for the coming decades

The top 100 global water questions: Results of a scoping exercise

Global water security presents a complex problem for human societies and will become more acute as the impacts of climate change escalate. Water security connects the practical water and sanitation challenges of households to the dynamics of global hydroclimates and ecosystems in the Anthropocene. To ensure the successful deployment of attention and resources, it is necessary to identify the most pressing questions for water research. Here, we present the results of a scoping exercise conducted across the global water sector. More than 400 respondents submitted an excess of 4,000 potential questions. Drawing on expert analysis, we highlight 100 indicative research questions across six thematic domains: water and sanitation for human settlements; water and sanitation safety risk management; water security and scarcity; hydroclimate-ecosystem-Anthropocene dynamics; multi-level governance; and knowledge production. These questions offer an interdisciplinary and multi-scalar framework for guiding the nature and space of water research for the coming decades

Womens' opinions on antenatal care in developing countries: results of a study in Cuba, Thailand, Saudi Arabia and Argentina

BACKGROUND: The results of a qualitative study carried out in four developing countries (Cuba, Thailand, Saudi Arabia and Argentina) are presented. The study was conducted in the context of a randomised controlled trial to test the benefits of a new antenatal care protocol that reduced the number of visits to the doctor, rationalised the application of technology, and improved the provision of information to women in relation to the traditional protocol applied in each country. METHODS: Through focus groups discussions we were able to assess the concepts and expectations underlying women's evaluation of concepts and experiences of the care received in antenatal care clinics. 164 women participated in 24 focus groups discussion in all countries. RESULTS: Three areas are particularly addressed in this paper: a) concepts about pregnancy and health care, b) experience with health services and health providers, and c) opinions about the modified Antenatal Care (ANC) programme. In all three topics similarities were identified as well as particular opinions related to country specific social and cultural values. In general women have a positive view of the new ANC protocol, particularly regarding the information they receive. However, controversial issues emerged such as the reduction in the number of visits, particularly in Cuba where women are used to have 18 ANC visits in one pregnancy period. CONCLUSION: Recommendations to improve ANC services performance are being proposed. Any country interested in the application of a new ANC protocol should regard the opinion and acceptability of women towards changes