Improved Firefly Algorithm with Variable Neighborhood Search for Data Clustering

من بين الخوارزميات الأدلة العليا (الميتاهيورستك)، تعد الخوارزميات القائمة على البحوث المتعددة (المجتمع) خوارزمية بحث استكشافية متفوقة كخوارزمية البحث المحلية من حيث استكشاف مساحة البحث للعثور على الحلول المثلى العالمية. ومع ذلك، فإن الجانب السلبي الأساسي للخوارزميات القائمة على البحوث المتعددة (المجتمع) هو قدرتها الاستغلالية المنخفضة، مما يمنع توسع منطقة البحث عن الحلول المثلى. خوارزمية اليَرَاعَة المضيئة (Firefly (FA هي خوارزمية تعتمد على المجتمع والتي تم استخدامها على نطاق واسع في مشاكل التجميع. ومع ذلك، فإن FA مقيد بتقاربها السابق لأوانه عندما لا يتم استخدام استراتيجيات بحث محلي لتحسين جودة حلول المجموعات في منطقة المجاورة واستكشاف المناطق العالمية في مساحة البحث. على هذا الأساس، فإن الهدف من هذا العمل هو تحسين FA باستخدام البحث المتغير في الأحياء (VNS) كطريقة بحث محلية (FA-VNS)، وبالتالي توفير فائدة VNS للمفاضلة بين قدرات الاستكشاف والاستغلال. يسمح FA-VNS المقترح لليراعات بتحسين حلول التجميع مع القدرة على تعزيز حلول التجميع والحفاظ على تنوع حلول التجميع أثناء عملية البحث باستخدام مشغلي الاضطراب في VNS. لتقييم أداء الخوارزمية، يتم استخدام ثماني مجموعات بيانات معيارية مع أربع خوارزميات تجميع معروفة. تشير المقارنة وفقًا لمقاييس التقييم الداخلية والخارجية إلى أن FA-VNS المقترحة يمكن أن تنتج حلول تجميع أكثر إحكاما من خوارزميات التجميع المعروفة.Among the metaheuristic algorithms, population-based algorithms are an explorative search algorithm superior to the local search algorithm in terms of exploring the search space to find globally optimal solutions. However, the primary downside of such algorithms is their low exploitative capability, which prevents the expansion of the search space neighborhood for more optimal solutions. The firefly algorithm (FA) is a population-based algorithm that has been widely used in clustering problems. However, FA is limited in terms of its premature convergence when no neighborhood search strategies are employed to improve the quality of clustering solutions in the neighborhood region and exploring the global regions in the search space. On these bases, this work aims to improve FA using variable neighborhood search (VNS) as a local search method, providing VNS the benefit of the trade-off between the exploration and exploitation abilities. The proposed FA-VNS allows fireflies to improve the clustering solutions with the ability to enhance the clustering solutions and maintain the diversity of the clustering solutions during the search process using the perturbation operators of VNS. To evaluate the performance of the algorithm, eight benchmark datasets are utilized with four well-known clustering algorithms. The comparison according to the internal and external evaluation metrics indicates that the proposed FA-VNS can produce more compact clustering solutions than the well-known clustering algorithms

Modified ACS centroid memory for data clustering

Ant Colony Optimization (ACO) is a generic algorithm, which has been widely used in different application domains due to its simplicity and adaptiveness to different optimization problems. The key component that governs the search process in this algorithm is the management of its memory model. In contrast to other algorithms, ACO explicitly utilizes an adaptive memory, which is important to its performance in terms of producing optimal results. The algorithm’s memory records previous search regions and is fully responsible for transferring the neighborhood of the current structures to the next iteration. Ant Colony Optimization for Clustering (ACOC) is a swarm algorithm inspired from nature to solve clustering issues as optimization problems. However, ACOC defined implicit memory (pheromone matrix) inability to retain previous information on an ant’s movements in the pheromone matrix. The problem arises because ACOC is a centroid-label clustering algorithm, in which the relationship between a centroid and instance is unstable. The label of the current centroid value changes from one iteration to another because of changes in centroid label. Thus the pheromone values are lost because they are associated with the label (position) of the centroid. ACOC cannot transfer the current clustering solution to the next iterations due to the history of the search being lost during the algorithm run. This study proposes a new centroid memory (A-ACOC) for data clustering that can retain the information of a previous clustering solution. This is possible because the pheromone is associated with the adaptive instance and not with label of the centroid. Centroids will be identified based on the adaptive instance route. A comparison of the performance of several common clustering algorithms using real-world data sets shows that the accuracy of the proposed algorithm surpasses those of its counterparts