Scalable Evidential K-Nearest Neighbor Classification on Big Data

The K -Nearest Neighbor (K-NN) algorithm has garnered widespread utilization in real-world scenarios, due to its exceptional interpretability that other classification algorithms may not have. The evidential K-NN (EK-NN) algorithm builds upon the same nearest neighbor search procedure as K-NN, and provides more informative classification outcomes. However, EK-NN is not practical for Big Data because it is computationally complex. First, the search for K nearest neighbors of test samples from $n$ training samples requires $O(n^{2})$ operations. Additionally, estimating parameters involves performing complicated matrix calculations that increase in scale as the dataset becomes larger. To address these issues, we propose two scalable EK-NN classifiers, Global Exact EK-NN and Local Approximate EK-NN, under the distributed Spark framework. Along with the Local Approximate EK-NN, a new distributed gradient descent algorithm is developed to learn parameters. Data parallelism is used to reduce negative impacts caused by data distribution differences. Experimental results show that Our algorithms are able to achieve state-of-the-art scaling efficiency and accuracy on large datasets with more than 10 million samples.