Computing a few extreme singular triplets of a third-order tensor using the t-product

This paper describes software for computing a few of the largest or smallest singular triplets of a third-order tensor using the t-product. The software implements restarted partial tensor bidiagonalization techniques that were introduced by El Hachimi et al. in [Numer. Linear Algebra Appl., 31 (2024), Art. e2530]. Restarting is carried out by augmenting the available solution subspace by Ritz lateral slices or by harmonic Ritz lateral slices. The performance of our Python implementation is investigated. The software is designed for easy use in various applications.