Deconstructing the Big Valley Search Space Hypothesis

The big valley hypothesis suggests that, in combinatorial optimisation, local optima of good quality are clustered and surround the global optimum. We show here that the idea of a single valley does not always hold. Instead the big valley seems to de-construct into several valleys, also called ‘funnels’ in theoretical chemistry. We use the local optima networks model and propose an effective procedure for extracting the network data. We conduct a detailed study on four selected TSP instances of moderate size and observe that the big valley decomposes into a number of sub-valleys of different sizes and fitness distributions. Sometimes the global optimum is located in the largest valley, which suggests an easy to search landscape, but this is not generally the case. The global optimum might be located in a small valley, which offers a clear and visual explanation of the increased search difficulty in these cases. Our study opens up new possibilities for analysing and visualising combinatorial landscapes as complex networks

Deconstructing the Sanders Focus and the Sanders Phase : A Reply to Perttula Regarding the Taxonomy and Significance of the So-called Sanders Focus, or Sanders Phase, Pottery of Northeast Texas and Southeast Oklahoma

Perttula is correct in pointing out that there are numerical errors in a recently published table of mine. A revised version is presented here as Table 1. Although several of these errors are numerically large and might have caused problems had they gone uncorrected, Perttula is not correct in suggesting that they are serious in the sense that they have affected the conclusions I reached based on the table, the insinuation being that they weaken my Sanders entrepot hypothesis. They do not. That hypothesis is part of the reinterpretation of the archeology and bioanthropology of the Arkansas Valley and the Red River Valley which I have been developing for more than eight years. It could hardly be weakened by errors in this table which is simply a compilation of the pottery of the five so-called Sanders focus/phase types reported from the list of sites with probable Sanders phase components recently proffered by Bruseth, Wilson, and Perttula

Coarse-Grained Barrier Trees of Fitness Landscapes

Recent literature suggests that local optima in fitness landscapes are clustered, which offers an explanation of why perturbation-based metaheuristics often fail to find the global optimum: they become trapped in a sub-optimal cluster. We introduce a method to extract and visualize the global organization of these clusters in form of a barrier tree. Barrier trees have been used to visualize the barriers between local optima basins in fitness landscapes. Our method computes a more coarsely grained tree to reveal the barriers between clusters of local optima. The core element is a new variant of the flooding algorithm, applicable to local optima networks, a compressed representation of fitness landscapes. To identify the clusters, we apply a community detection algorithm. A sample of 200 NK fitness landscapes suggests that the depth of their coarse-grained barrier tree is related to their search difficulty

Communities of Local Optima as Funnels in Fitness Landscapes

We conduct an analysis of local optima networks extracted from fitness landscapes of the Kauffman NK model under iterated local search. Applying the Markov Cluster Algorithm for community detection to the local optima networks, we find that the landscapes consist of multiple clusters. This result complements recent findings in the literature that landscapes often decompose into multiple funnels, which increases their difficulty for iterated local search. Our results suggest that the number of clusters as well as the size of the cluster in which the global optimum is located are correlated to the search difficulty of landscapes. We conclude that clusters found by community detection in local optima networks offer a new way to characterize the multi-funnel structure of fitness landscapes

Additional Dimensions to the Study of Funnels in Combinatorial Landscapes

The global structure of travelling salesman's fitness landscapes has recently revealed the presence of multiple `funnels'. This implies that local optima are organised into several clusters, so that a particular local optimum largely belongs to a particular funnel. Such a global structure can increase search difficulty, especially, when the global optimum is located in a deep, narrow funnel. Our study brings more precision (and dimensions) to the notion of funnels with a data-driven approach using Local Optima Networks and the Chained Lin-Kernighan heuristic. We start by exploring the funnel 'floors', characterising them using the notion of communities from complex networks. We then analyse the more complex funnel 'basins'. Since their depth is relevant to search, we visualise them in 3D. Our study, across a set of TSP instances, reveals a multi-funnel structure in most of them. However, the specific topology varies across instances and relates to search difficulty. Finally, including a stronger perturbation into Chained Lin-Kernighan proved to smooth the funnel structure, reducing the number of funnels and enlarging the valley leading to global optima

Management of Cluster Policies: Case Studies of Japanese, German, and French Bio-clusters

This paper provides a detailed comparison of the following five cases of Japanese and European clusters in biotechnology: (1) Kobe Biomedical Innovation Cluster (KBIC) in Kobe (Japan), (2) Fuji Pharma Valley Cluster in Shizuoka Prefecture (Japan), (3) BioM Biotech Cluster in Munich (Germany), (4) BioRegion Rhine-Neckar in Heidelberg (Germany), and (5) Alsace BioValley Cluster in Strasbourg (France). We pay special attention to the cluster policy and its management by each region's core cluster management organization. Information on the focal clusters and the management of cluster policies has been obtained through interviews with the cluster directors and core staff in 2010 and 2011. We find several similarities and differences among the five cases of Japanese and European clusters. We also discuss how the management of cluster policies by the core management organizations may be related with the performance of regional clusters.management, cluster policy, regional cluster, R&D, biotechnology, international comparison

Understanding Phase Transitions with Local Optima Networks: Number Partitioning as a Case Study

Phase transitions play an important role in understanding search difficulty in combinatorial optimisation. However, previous attempts have not revealed a clear link between fitness landscape properties and the phase transition. We explore whether the global landscape structure of the number partitioning problem changes with the phase transition. Using the local optima network model, we analyse a number of instances before, during, and after the phase transition. We compute relevant network and neutrality metrics; and importantly, identify and visualise the funnel structure with an approach (monotonic sequences) inspired by theoretical chemistry. While most metrics remain oblivious to the phase transition, our results reveal that the funnel structure clearly changes. Easy instances feature a single or a small number of dominant funnels leading to global optima; hard instances have a large number of suboptimal funnels attracting the search. Our study brings new insights and tools to the study of phase transitions in combinatorial optimisation

Comparing Communities of Optima with Funnels in Combinatorial Fitness Landscapes

The existence of sub-optimal funnels in combinatorial fitness landscapes has been linked to search difficulty. The exact nature of these structures — and how commonly they appear — is not yet fully understood. Improving our understanding of funnels could help with designing effective diversification mechanisms for a ‘smoothing’ effect, making optimisation easier. We model fitness landscapes as local optima networks. The relationship between communities of local optima found by network clustering algorithms and funnels is explored. Funnels are identified using the notion of monotonic sequences from the study of energy landscapes in theoretical chemistry. NK Landscapes and the Quadratic Assignment Problem are used as case studies. Our results show that communities are linked to funnels. The analysis exhibits relationships between these landscape structures and the performance of trajectory-based metaheuristics such as Simulated Annealing (SA) and Iterated Local Search (ILS). In particular, ILS gets trapped in funnels, and modular communities of optima slow it down. The funnels contribute to lower success for SA. We show that increasing the strength of ILS perturbation helps to ‘smooth’ the funnels and improves performance in multi-funnel landscapes.Authors listed as ECOM Trac

Deconstructing Feminine and Feminist Fantastic through the Study of Living Dolls

In her Deconstructing Feminine and Feminine Fantastic through the Study of Living Dolls, Raquel Velázquez analyzes the treatment of one idiosyncratic image within the fantastic genre, and one that also has a special impact on the configuration of the feminine: the doll. On the one hand, she examines the evolution of this fantastic motif in order to determine whether it involves a transformation of how the feminine fantastic is represented. On the other hand, she establishes some correlations between the image of the fantastic doll, and the development of processes such as the dollification of women or the humanization of the doll as it is identified in contemporary society. This is seen as an exemplification of how both the alleged feminine fantastic (which is questioned here), and the feminist fantastic adjust, alter, or adapt, in the same way as the society in which it is contextualized or integrated