Optimum-path Forest Algorithm Research Articles

Slope Stability Prediction Using k-NN-Based Optimum-Path Forest Approach

Slope instability can lead to catastrophic consequences. However, predicting slope stability effectively is still challenging because of the complex mechanisms and multiple influencing factors. In recent years, machine learning (ML) has received great attention in slope stability prediction due to its strong nonlinear prediction ability. In this study, an optimum-path forest algorithm based on k-nearest neighbor (OPFk-NN) was used to predict the stability of slopes. First, 404 historical slopes with failure risk were collected. Subsequently, the dataset was used to train and test the algorithm based on randomly divided training and test sets, respectively. The hyperparameter values were tuned by combining ten-fold cross-validation and grid search methods. Finally, the performance of the proposed approach was evaluated based on accuracy, F1-score, area under the curve (AUC), and computational burden. In addition, the prediction results were compared with the other six ML algorithms. The results showed that the OPFk-NN algorithm had a better performance, and the values of accuracy, F1-score, AUC, and computational burden were 0.901, 0.902, 0.901, and 0.957 s, respectively. Moreover, the failed slope cases can be accurately identified, which is highly critical in slope stability prediction. The slope angle had the most important influence on prediction results. Furthermore, the engineering application results showed that the overall predictive performance of the OPFk-NN model was consistent with the factor of safety value of engineering slopes. This study can provide valuable guidance for slope stability analysis and risk management.

Review of Non-Technical Losses Identification Techniques

Illegally consumption of electric power, termed as non-technical losses for the distribution companies is one of the dominant factors all over the world for many years. Although there are some conventional methods to identify these irregularities, such as physical inspection of meters at the consumer premises etc, but it requires large number of manpower and time; then also it does not seem to be adequate. Now a days there are various methods and algorithms have been developed that are proposed in different research papers, to detect non-technical losses. In this paper these methods are reviewed, their important features are highlighted and also the limitations are identified. Finally, the qualitative comparison of various non-technical losses identification algorithms is presented based on their performance, costs, data handling, quality control and execution times. It can be concluded that the graph-based classifier, Optimum-Path Forest algorithm that have both supervised and unsupervised variants, yields the most accurate result to detect non-technical losses.

A strong coreset algorithm to accelerate OPF as a graph-based machine learning in large-scale problems

Optimum-path forest (OPF) is one of the efficient graph-based frameworks that can determine the patterns of input dataset by extracting the optimal partitions of graph obtained through encoding data into a graph. Since OPF was introduced based on simple assumptions without considering the requirements of large-scale problems, this machine learning is an effective algorithm only for a reasonable size of input datasets. To provide a scalable OPF, this study introduces a strong coreset for accelerating OPF algorithm. Applying this approach can expedite OPF procedure, especially when it is working on massive datasets. Accordingly, a novel algebra is developed to represent the problem of OPF as an optimization problem for the proposed coreset definition. A novel coreset construction algorithm that can approximate the OPF solutions is subsequently proposed in order to improve the OPF construction speed. The simulation results of diverse experiments on various benchmark datasets illustrate computation gain and superiority of the proposed algorithm in terms of the construction and classification speeds as compared to the original algorithm while displaying reliably accurate performance. The presented coreset construction algorithm performs the training and testing phases of OPF up to 6.1 and 4.9 times faster than before, respectively.

Hybrid of anomaly-based and specification-based IDS for Internet of Things using unsupervised OPF based on MapReduce approach

Internet of Things (IoT) is a novel paradigm in computer networks in which resource-constrained objects connect to unreliable Internet by using a wide range of technologies. The insecure nature of the Internet and wireless sensor networks, that are the main components of IoT, make IoT vulnerable to different attacks, especially routing attacks (as insider attacks). A novel real-time hybrid intrusion detection framework is proposed in this study that consists of anomaly-based and specification-based intrusion detection modules for detecting two well-known routing attacks in IoT called sinkhole and selective-forwarding attacks. For this purpose, the specification-based intrusion detection agents, that are located in the router nodes, analyze the behavior of their host nodes and send their local results to the root node through normal data packets. In addition, an anomaly-based intrusion detection agent, that is located in the root node, employs the unsupervised optimum-path forest algorithm for projecting clustering models by using incoming data packets. This agent, which is based on the MapReduce architecture, can work in a distributed platform for projecting clustering models and consequently parallel detecting of anomalies as a global detection approach. The proposed method makes decision about suspicious behavior by using a voting mechanism. Notably, the proposed method is also extended to detect wormhole attack. The deployment of the hybrid proposed model is investigated in a smart-city scenario by an existing platform, as well. The free network's scale and the ability to identify malicious nodes are two key features of the proposed framework that are evaluated through different experiments in this study. The experimental results of simulated scenarios showed that the proposed hybrid method can achieve true positive rate of 76.19% and false positive rate of 5.92% when both sinkhole and selective-forwarding attacks were launched simultaneously. These rates in detecting wormhole attack are 96.02% and 2.08%, respectively.

Modification of supervised OPF-based intrusion detection systems using unsupervised learning and social network concept

Optimum-path forest (OPF) is a graph-based machine learning method that can overcome some limitations of the traditional machine learning algorithms that have been used in intrusion detection systems. This paper presents a novel approach for intrusion detection using a modified OPF (MOPF) algorithm for improving the performance of traditional OPF in terms of detection rate (DR), false alarm rate (FAR), and time of execution. To address the problem of scalability in large datasets and also for achieving high attack recognition rates, the proposed framework employs the k-means clustering algorithm, as a partitioning module, for generating different homogeneous training subsets from original heterogeneous training samples. In the proposed MOPF algorithm, the distance between unlabeled samples and the root (prototype) of every sample in OPF is also considered in classifying unlabeled samples with the aim of improving the accuracy rate of traditional OPF algorithm. Moreover, the centrality and the prestige concepts in the social network analysis are employed in a pruning module for determining the most informative samples in training subsets to speed up the traditional OPF algorithm. The experimental results on NSL-KDD dataset show that the proposed method performs better than traditional OPF in terms of accuracy rate, DR, FAR, and cost per example (CPE) evaluation metrics.

Retrieval of clothing images based on relevance feedback with focus on collar designs

The content-based image retrieval methods are developed to help people find what they desire based on preferred images instead of linguistic information. This paper focuses on capturing the image features representing details of the collar designs, which is important for people to choose clothing. The quality of the feature extraction methods is important for the queries. This paper presents several new methods for the collar-design feature extraction. A prototype of clothing image retrieval system based on relevance feedback approach and optimum-path forest algorithm is also developed to improve the query results and allows users to find clothing image of more preferred design. A series of experiments are conducted to test the qualities of the feature extraction methods and validate the effectiveness and efficiency of the RF-OPF prototype from multiple aspects. The evaluation scores of initial query results are used to test the qualities of the feature extraction methods. The average scores of all RF steps, the average numbers of RF iterations taken before achieving desired results and the score transition of RF iterations are used to validate the effectiveness and efficiency of the proposed RF-OPF prototype.

Recognition of handwritten digits using the signature features and Optimum-Path Forest Classifier

There is a growing need for recognition of digits manuscripts for use in various situations, such as recognition of handwritten postal address digits for automated redirection of letters in the mail, acknowledgment of nominal values in bank checks. Recognition of handwritten digits faces great difficulty in dealing with intra-class variation due to different writing styles, different degrees of inclination of the characters. Optical character recognition systems, also known as OCR, identifying and recognizing printed characters through images, an already widespread functionality in scanners, mobile devices, among others. This paper presents the use of the classifier Optimum-Path Forest (OPF) applied in handwriting recognition digits. A new feature extraction method is proposed using signature of the characters, and the OPF algorithm is used in the classification. According to the results presented, it appears that the detection and recognition of characters are being carried out satisfactorily in the Manhattan distance stood out with an average accuracy of 99.53%, and get training times and test lower than the other methods such as It is the characteristic of OPF method.

Multi-View Video Summarization Using Bipartite Matching Constrained Optimum-Path Forest Clustering

The task of multi-view video summarization is to efficiently represent the most significant information from a set of videos captured for a certain period of time by multiple cameras. The problem is highly challenging because of the huge size of the data, presence of many unimportant frames with low activity, inter-view dependencies, and significant variations in illumination. In this paper, we propose a graph-theoretic solution to the above problems. Semantic feature in form of visual bag of words and visual features like color, texture, and shape are used to model shot representative frames after temporal segmentation . Gaussian entropy is then applied to filter out frames with low activity. Inter-view dependencies are captured via bipartite graph matching. Finally, the optimum-path forest algorithm is applied for the clustering purpose. Subjective as well as objective evaluations clearly indicate the effectiveness of the proposed approach.

A nature-inspired approach to speed up optimum-path forest clustering and its application to intrusion detection in computer networks

We propose a nature-inspired approach to estimate the probability density function (pdf) used for data clustering based on the optimum-path forest algorithm (OPFC). OPFC interprets a dataset as a graph, whose nodes are the samples and each sample is connected to its k-nearest neighbors in a given feature space (a k-nn graph). The nodes of the graph are weighted by their pdf values and the pdf is computed based on the distances between the samples and their k-nearest neighbors. Once the k-nn graph is defined, OPFC finds one sample (root) at each maximum of the pdf and propagates one optimum-path tree (cluster) from each root to the remaining samples of its dome. Clustering effectiveness will depend on the pdf estimation, and the proposed approach efficiently computes the best value of k for a given application. We validate our approach in the context of intrusion detection in computer networks. First, we compare OPFC with data clustering based on k-means, and self-organization maps. Second, we evaluate several metaheuristic techniques to find the best value of k.

Links Between Image Segmentation Based on Optimum-Path Forest and Minimum Cut in Graph

Image segmentation can be elegantly solved by optimum-path forest and minimum cut in graph. Given that both approaches exploit similar image graphs, some comparative analysis is expected between them. We clarify their differences and provide their comparative analysis from the theoretical point of view, for the case of binary segmentation (object/background) in which hard constraints (seeds) are provided interactively. Particularly, we formally prove that some optimum-path forest methods from two distinct region-based segmentation paradigms, with internal and external seeds and with only internal seeds, indeed minimize some graph-cut measures. This leads to a proof of the necessary conditions under which the optimum-path forest algorithm and the min-cut/max-flow algorithm produce exactly the same segmentation result, allowing a comparative analysis between them.