Non-Gradient Hash Factor Learning for High-Dimensional and Incomplete Data Representation Learning

High-dimensional and incomplete (HDI) data are ubiquitous in various Big Data-related industrial applications, such as drug innovation and recommender systems. Hash-learning is the most efficient representation learning approach to extract hidden information from HDI data owing to its fast reasoning and low storage. However, an existing hash learning approach commonly employs gradient-based optimization techniques to address the discrete objective caused by the binary nature of hash factors, where the Quantization (i.e., quantizing the real values to binary codes) loss is inevitable, resulting in accuracy loss when representing HDI data. Motivated by these critical and vital issues, this paper proposes a non-gradient hash factor (NGHF) model with three-fold ideas: a) innovating a discrete differential evolution (DDE) algorithm able to simulate the continuous optimization via disabling bits of binary codes based on the projected Hamming dissimilarity, thus enabling an effective discrete optimizer, b) applying the proposed DDE algorithm to directly optimize the discrete learning objective of NGHF defined on HDI data, thereby facilitating its efficient and precise training without any Quantization loss, and c) theoretically proving the convergence of NGHF. As such, NGHF possesses high representation learning ability comparable to that of a real-valued model, making it able to achieve precise binary representation to HDI data. Extensive experimental results on nine real-world datasets demonstrate that NGHF significantly outperforms eight state-of-the-art hash learning models. Moreover, its accuracy is amazingly comparable to that of a real-valued model for HDI data representation learning.