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This paper explores variants of the subspace iteration algorithm for computing approximate invariant subspaces. The standard subspace iteration approach is revisited and new variants that exploit gradient-type techniques combined with a…

Numerical Analysis · Mathematics 2024-05-14 Foivos Alimisis , Yousef Saad , Bart Vandereycken

Block Gram-Schmidt algorithms serve as essential kernels in many scientific computing applications, but for many commonly used variants, a rigorous treatment of their stability properties remains open. This work provides a comprehensive…

Numerical Analysis · Mathematics 2023-02-21 Erin Carson , Kathryn Lund , Miroslav Rozložník , Stephen Thomas

This work considers multirate generalized-structure additively partitioned Runge-Kutta (MrGARK) methods for solving stiff systems of ordinary differential equations (ODEs) with multiple time scales. These methods treat different partitions…

Numerical Analysis · Mathematics 2022-01-19 Steven Roberts , John Loffeld , Arash Sarshar , Carol S. Woodward , Adrian Sandu

Solving large-scale linear systems problems is a cornerstone in scientific and industrial computing. Classical iterative solvers face increasing difficulty as the number of unknowns becomes large, while fully quantum linear solvers require…

Quantum Physics · Physics 2026-04-14 Shigetora Miyashita , Yoshi-aki Shimada

Iterative methods for solving large sparse systems of linear equations are widely used in many HPC applications. Extreme scaling of these methods can be difficult, however, since global communication to form dot products is typically…

Mathematical Software · Computer Science 2020-09-29 Nick Brown , J. Mark Bull , Iain Bethune

Generalized Additive Runge-Kutta schemes have shown to be a suitable tool for solving ordinary differential equations with additively partitioned right-hand sides. This work develops symplectic GARK schemes for additively partitioned…

Numerical Analysis · Mathematics 2023-12-14 Michael Günther , Adrian Sandu , Kevin Schäfers , Antonella Zanna

We introduce an iterative method named GPMR for solving 2x2 block unsymmetric linear systems. GPMR is based on a new process that reduces simultaneously two rectangular matrices to upper Hessenberg form and that is closely related to the…

Numerical Analysis · Mathematics 2021-11-16 Alexis Montoison , Dominique Orban

We present a systematic pathway for solving differential equations within the quantum linear systems framework by combining block encoding with Quantum Singular Value Transformation (QSVT). The approach is demonstrated on a complex…

Quantum Physics · Physics 2026-05-12 Abhishek Setty

We introduce two iterative methods, GPBiLQ and GPQMR, for solving unsymmetric partitioned linear systems. The basic mechanism underlying GPBiLQ and GPQMR is a novel simultaneous tridiagonalization via biorthogonality that allows for…

Numerical Analysis · Mathematics 2024-01-08 Kui Du , Jia-Jun Fan , Fang Wang

We present an overview of randomized orthogonalization techniques that construct a well-conditioned basis whose sketch is orthonormal. Randomized orthogonalization has recently emerged as a powerful paradigm for reducing the computational…

Numerical Analysis · Mathematics 2025-12-18 Jean-Guillaume de Damas , Laura Grigori , Igor Simunec , Edouard Timsit

The Coupled Cluster (CC) method is used to compute the electronic correlation energy in atoms and molecules and often leads to highly accurate results. However, due to its single-reference nature, standard CC in its projected form fails to…

In recent years two Krylov subspace methods have been proposed for solving skew symmetric linear systems, one based on the minimum residual condition, the other on the Galerkin condition. We give new, algorithm-independent proofs that in…

Numerical Analysis · Mathematics 2015-12-02 Stanley C. Eisenstat

In this paper, we develop algorithms for computing the recurrence coefficients corresponding to multiple orthogonal polynomials on the step-line. We reformulate the problem as an inverse eigenvalue problem, which can be solved using…

Numerical Analysis · Mathematics 2026-03-05 Amin Faghih , Michele Rinelli , Marc Van Barel , Raf Vandebril , Robbe Vermeiren

This paper introduces and analyzes an original class of Krylov subspace methods that provide an efficient alternative to many well-known conjugate-gradient-like (CG-like) Krylov solvers for square nonsymmetric linear systems arising from…

Numerical Analysis · Mathematics 2017-09-13 Silvia Gazzola , Paolo Novati

Classical iterative methods for tomographic reconstruction include the class of Algebraic Reconstruction Techniques (ART). Convergence of these stationary linear iterative methods is however notably slow. In this paper we propose the use of…

Numerical Analysis · Mathematics 2015-01-22 Siegfried Cools , Pieter Ghysels , Wim van Aarle , J. Sijbers , Wim Vanroose

Lattice QCD calculations require significant computational effort, with the dominant fraction of resources typically spent in the numerical inversion of the Dirac operator. One of the simplest methods to solve such large and sparse linear…

High Energy Physics - Lattice · Physics 2021-12-01 Salvatore Cali , William Detmold , Grzegorz Korcyl , Piotr Korcyl , Phiala Shanahan

Complex-variable matrix optimization problems (CMOPs) in Frobenius norm emerge in many areas of applied mathematics and engineering applications. In this letter, we focus on solving CMOPs by iterative methods. For unconstrained CMOPs, we…

Numerical Analysis · Mathematics 2023-04-06 Sai Wang , Yi Gong

This paper presents the results of a preliminary experimental investigation of the performance of a stationary iterative method based on a block staircase splitting for solving singular systems of linear equations arising in Markov chain…

Numerical Analysis · Mathematics 2023-02-16 V. Besozzi , M. Della Bartola , L. Gemignani

In this paper we introduce a parameter dependent class of Krylov-based methods, namely CD, for the solution of symmetric linear systems. We give evidence that in our proposal we generate sequences of conjugate directions, extending some…

Numerical Analysis · Mathematics 2014-08-27 Giovanni Fasano

Many quantum algorithms for attacking symmetric cryptography involve the rank problem of quantum linear equations. In this paper, we first propose two quantum algorithms for solving quantum linear systems of equations with coherent…

Quantum Physics · Physics 2024-05-14 Qiqing Xia , Qianru Zhu , Huiqin Xie , Li Yang