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The efficient and accurate QR decomposition for matrices with hierarchical low-rank structures, such as HODLR and hierarchical matrices, has been challenging. Existing structure-exploiting algorithms are prone to numerical instability as…

Numerical Analysis · Mathematics 2018-09-28 Daniel Kressner , Ana Susnjara

The unpivoted and pivoted Householder QR factorizations are ubiquitous in numerical linear algebra. A difficulty with pivoted Householder QR is the communication bottleneck introduced by pivoting. In this paper we propose using random…

Numerical Analysis · Mathematics 2017-03-08 Stephen Becker , James Folberth , Laura Grigori

Quantum signal processing and quantum singular value transformation are powerful tools to implement polynomial transformations of block-encoded matrices on quantum computers, and has achieved asymptotically optimal complexity in many…

Quantum Physics · Physics 2026-04-01 Xi Lu , Yuan Liu , Hongwei Lin

The rational QZ method generalizes the QZ method by implicitly supporting rational subspace iteration. In this paper we extend the rational QZ method by introducing shifts and poles of higher multiplicity in the Hessenberg pencil, which is…

Numerical Analysis · Mathematics 2021-08-11 Thijs Steel , Daan Camps , Karl Meerbergen , Raf Vandebril

We address the task of higher-order derivative evaluation of computer programs that contain QR decompositions and real symmetric eigenvalue decompositions. The approach is a combination of univariate Taylor polynomial arithmetic and matrix…

Numerical Analysis · Mathematics 2010-10-01 Sebastian F. Walter , Lutz Lehmann , René Lamour

Randomized sampling has recently been proven a highly efficient technique for computing approximate factorizations of matrices that have low numerical rank. This paper describes an extension of such techniques to a wider class of matrices…

Numerical Analysis · Mathematics 2015-03-25 Per-Gunnar Martinsson

We present a novel algorithm for performing the Cartan-Khaneja-Glaser decomposition of unitary matrices in $SU(2^n)$, a critical task for efficient quantum circuit design. Building upon the approach introduced by S\'a Earp and Pachos…

Given a matrix $A$ of size $m\times n$, the manuscript describes a algorithm for computing a QR factorization $AP=QR$ where $P$ is a permutation matrix, $Q$ is orthonormal, and $R$ is upper triangular. The algorithm is blocked, to allow it…

Numerical Analysis · Mathematics 2015-06-01 P. G. Martinsson

As the most central and computationally intensive component of deep neural networks, the execution efficiency of matrix multiplication directly determines the training and inference performance of models. Harnessing the parallel processing…

Quantum Physics · Physics 2026-05-25 Jiaqi Yao , Tianjian Huang , Zipeng Cai , Ding Liu

The QR-algorithm is one of the most important algorithms in linear algebra. Its several variants make feasible the computation of the eigenvalues and eigenvectors of a numerical real or complex matrix, even when the dimensions of the matrix…

Numerical Analysis · Mathematics 2020-09-02 Avinash Kulkarni , Tristan Vaccon

Efficient task scheduling is paramount in parallel programming on multi-core architectures, where tasks are fundamental computational units. QR factorization is a critical sub-routine in Sequential Least Squares Quadratic Programming…

Distributed, Parallel, and Cluster Computing · Computer Science 2025-06-12 Soumyajit Chatterjee , Rahul Utkoor , Uppu Eshwar , Sathya Peri , V. Krishna Nandivada

The efficient implementation of matrix arithmetic operations underpins the speedups of many quantum algorithms. We develop a suite of methods to perform matrix arithmetics -- with the result encoded in the off-diagonal blocks of a…

Quantum Physics · Physics 2026-01-23 Christopher Kang , Yuan Su

This paper is concerned with the reduction of a unitary matrix U to CMV-like shape. A Lanczos--type algorithm is presented which carries out the reduction by computing the block tridiagonal form of the Hermitian part of U, i.e., of the…

Numerical Analysis · Mathematics 2016-07-27 Roberto Bevilacqua , Gianna M. Del Corso , Luca Gemignani

In this work, we develop a new fast algorithm, spaQR -- sparsified QR, for solving large, sparse linear systems. The key to our approach is using low-rank approximations to sparsify the separators in a Nested Dissection based Householder QR…

Numerical Analysis · Mathematics 2020-10-15 Abeynaya Gnanasekaran , Eric Darve

Solving linear systems and computing eigenvalues are two fundamental problems in linear algebra. For solving linear systems, many efficient quantum algorithms have been discovered. For computing eigenvalues, currently, we have efficient…

Quantum Physics · Physics 2020-09-22 Changpeng Shao

We present a class of fast subspace tracking algorithms based on orthogonal iterations for structured matrices/pencils that can be represented as small rank perturbations of unitary matrices. The algorithms rely upon an updated data sparse…

Numerical Analysis · Mathematics 2021-04-23 Roberto Bevilacqua , Gianna M. Del Corso , Luca Gemignani

The variational quantum eigensolver has been proposed as a low-depth quantum circuit that can be employed to examine strongly correlated systems on today's noisy intermediate-scale quantum computers. We examine details associated with the…

Quantum Physics · Physics 2020-08-26 Luogen Xu , Joseph T. Lee , J. K. Freericks

New real structure-preserving decompositions are introduced to develop fast and robust algorithms for the (right) eigenproblem of general quaternion matrices. Under the orthogonally JRS-symplectic transformations, the Francis JRS-QR step…

Numerical Analysis · Mathematics 2020-11-10 Zhigang Jia , Musheng Wei , Meixiang Zhao , Yong Chen

We propose a rational QZ method for the solution of the dense, unsymmetric generalized eigenvalue problem. This generalization of the classical QZ method operates implicitly on a Hessenberg, Hessenberg pencil instead of on a Hessenberg,…

Numerical Analysis · Mathematics 2020-05-20 Daan Camps , Karl Meerbergen , Raf Vandebril

Joint diagonalization, the process of finding a shared set of approximate eigenvectors for a collection of matrices, arises in diverse applications such as multidimensional harmonic analysis or quantum information theory. This task is…

Optimization and Control · Mathematics 2025-02-12 Erik Troedsson , Marcus Carlsson , Herwig Wendt