Ying Ji , Yuehua Feng , Yongxin Dong , Jinrui Guan , Xiao Han
{"title":"Low-rank approximation: Randomized QR with Column Pivoting and related methods using sparse projection and pass-efficient techniques","authors":"Ying Ji , Yuehua Feng , Yongxin Dong , Jinrui Guan , Xiao Han","doi":"10.1016/j.cam.2025.117091","DOIUrl":"10.1016/j.cam.2025.117091","url":null,"abstract":"<div><div>Currently, several efficient algorithms utilize randomization techniques to compute low-rank matrix approximations, such as Randomized QR with Column Pivoting (RQRCP) and Flip-Flop spectrum-revealing QR (FFSRQR). While these algorithms have achieved notable efficiency in dealing with large-scale low-rank matrix approximations, there is still scope for improvement. This paper introduces an improved version of the RQRCP algorithm, enhanced by incorporating a sparse embedding matrix (SEM) for sparse projection, referred to as RQRCP-SEM. Furthermore, building on RQRCP-SEM and employing pass-efficient techniques, this paper proposes two versions of the PEFFSRQR-SEM algorithm to further optimize the efficiency of the FFSRQR algorithm. The paper theoretically analyzes the approximation error and computational complexity of these new algorithms and validates these analyses through numerical experiments.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117091"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Inexact block triangular preconditioners for double saddle-point systems arising from coupled Stokes–Darcy model","authors":"Siqi Liang, Na Huang","doi":"10.1016/j.cam.2025.117079","DOIUrl":"10.1016/j.cam.2025.117079","url":null,"abstract":"<div><div>The interaction between fluids in porous media and free flow regions is significant in various fields such as geology, environmental engineering, and petroleum engineering. This problem can be modeled using a coupled system of Stokes equations and Darcy’s law. Finite element discretization of the coupled Stokes–Darcy model results in a double saddle-point system. In this work, we propose a class of inexact block three-by-three triangular preconditioners for these discretized saddle-point systems by fully utilizing their special structure. When used to precondition Krylov subspace methods, each step requires solving only three simple symmetric positive definite linear subsystems. Additionally, we derive explicit and sharp spectral bounds for the preconditioned matrices and show that all eigenvalues have positive real parts. Numerical experiments demonstrate the effectiveness and robustness of our preconditioners in solving the coupled Stokes–Darcy model.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117079"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Codes equipped with non-cyclic burst-b distance, bounds and periodical burst errors","authors":"Pankaj Kumar Das, Achal Agarwal","doi":"10.1016/j.cam.2025.117081","DOIUrl":"10.1016/j.cam.2025.117081","url":null,"abstract":"<div><div>In this paper, we present a study on codes equipped with non-cyclic burst-<span><math><mi>b</mi></math></span> distance. We mainly study bounds on the maximum number of codewords possible in such a code, as well as the codes’ periodical burst detection- and -correction capability. For such a code, we derive the Litsyn-Laihonen type of bound and its improved version. We also present the asymptotic form of Litsyn-Laihonen type bound and make a comparison with all the previously known asymptotic bounds. We also provide periodical burst detection- and -correction capability for such a code in general and then for a special code. Finally, we give a decoding procedure for the special code along with its computational complexity.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117081"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The backward problem of a stochastic space-fractional diffusion equation driven by fractional Brownian motion","authors":"Fan Yang, Lu-Lu Yan, Xiao-Xiao Li","doi":"10.1016/j.cam.2025.117086","DOIUrl":"10.1016/j.cam.2025.117086","url":null,"abstract":"<div><div>This paper is concerned with a backward problem of a stochastic space-fractional diffusion equation. The source term is driven by fractional Brownian motion. The well-posedness of the forward problem is studied at first. The backward problem is ill-posed, i.e., the solution of this problem does not depend continuously on the data. The instability is discussed in the sense of expectation and variance. A truncated regularization method is used to solve the backward problem. Under the a priori and the a posteriori regularization parameter choice rules, the error estimates between the regularization solution and the exact solution are obtained, respectively. Different numerical examples are presented to illustrate the validity and effectiveness of our method.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117086"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Componentwise and normwise perturbation analysis for the anti-triangular Schur decomposition","authors":"Jia Yan Wu , Xiao Shan Chen , Hai–Wei Sun","doi":"10.1016/j.cam.2025.117092","DOIUrl":"10.1016/j.cam.2025.117092","url":null,"abstract":"<div><div>This paper presents componentwise and new normwise perturbation bounds for the anti-triangular Schur decomposition of a square matrix. In particular, we derive sensitivity estimates and condition numbers of eigenvalues and <span><math><mi>Z</mi></math></span>-isotropic subspaces and improve the normwise condition number of such decomposition given by Chen, Li and Ng [SIAM J. Matrix Anal., 33(2012): 325–335]. Numerical examples are given to test the obtained bounds.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117092"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Convergence analysis of a PINNs-based approach to the inverse source problem of the heat equation with local measurements","authors":"Xuezhao Zhang, Zhiyuan Li","doi":"10.1016/j.cam.2025.117077","DOIUrl":"10.1016/j.cam.2025.117077","url":null,"abstract":"<div><div>This paper investigates the problem of recovering the spatial distribution of the source term in a parabolic system from local measurement data. We propose a method based on Physics-Informed Neural Networks (PINNs) to approximate the solution of this inverse problem. Within this framework, we design a novel loss function that incorporates the residuals of the partial differential equation (PDE), measurement data residuals, as well as residuals from initial–boundary conditions and boundary derivatives. These additional terms enhance the regularity of the solution to address the ill-posedness of the inverse problem. Based on the conditional stability of the inverse problem, we demonstrate that the neural network can effectively approximate its solution, and we further establish generalization error estimates for the source term, which depend on the training error and data noise level, while also verifying the convergence of the network. A series of numerical experiments further validate the effectiveness and robustness of the proposed method, showing that it achieves high accuracy and efficiency under noisy data and varying measurement conditions.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117077"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A derivative-free spectral residual method for computing generalized eigenpairs of weakly symmetric tensors","authors":"Ruijuan Zhao , Maolin Liang , Yangyang Xu , Qun Li","doi":"10.1016/j.cam.2025.117088","DOIUrl":"10.1016/j.cam.2025.117088","url":null,"abstract":"<div><div>This paper is concerned with computing generalized eigenpairs of weakly symmetric tensors. We first show that computing generalized eigenpairs of weakly symmetric tensors is equivalent to finding the nonzero solutions of a nonlinear system of equations, and then propose a derivative-free spectral residual method for it. The method utilizes the residual vector as the search direction and incorporates a derivative-free nonmonotone line search strategy, avoiding any explicit information associated with the Jacobian matrix of the considered nonlinear system of equations. Additionally, the global convergence of the method is established. Numerical results are presented to demonstrate superior efficiency of the proposed method through comparisons with the alternating least squares (ALS) method and other existing approaches. Furthermore, the results show that the proposed method can capture more, and in some cases all, generalized eigenvalues of weakly symmetric tensors.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117088"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On numerical computation of inverses and determinants for generalized anti-tridiagonal Hankel matrices","authors":"Xin Fan, Ji-Teng Jia","doi":"10.1016/j.cam.2025.117076","DOIUrl":"10.1016/j.cam.2025.117076","url":null,"abstract":"<div><div>This paper investigates the inverses and determinants of generalized anti-tridiagonal Hankel matrices. We first present an explicit formula for the inverses of these matrices, based on tensor products and the inverses of general anti-tridiagonal Hankel matrices. An efficient algorithm for matrix inversion is then proposed, reducing memory requirements for storing these matrices and simplifying analysis by leveraging the properties of tensor products. Additionally, we introduce a cost-effective algorithm for computing the determinants of generalized anti-tridiagonal Hankel matrices, transforming the problem into that of lower-order anti-tridiagonal Hankel matrix determinants. We also derive an explicit formula for determinant evaluation. Numerical results from MATLAB simulations demonstrate the accuracy, efficiency, and performance of the proposed algorithms, which are compared to MATLAB built-in functions, showing clear advantages in computational accuracy and speed.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117076"},"PeriodicalIF":2.6,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhuo-Heng He , Yun-Ze Xu , Qing-Wen Wang , Xiang-Xiang Wang
{"title":"Solving a system of quaternion matrix equations by using PSVD for multiple matrices with applications","authors":"Zhuo-Heng He , Yun-Ze Xu , Qing-Wen Wang , Xiang-Xiang Wang","doi":"10.1016/j.cam.2025.117072","DOIUrl":"10.1016/j.cam.2025.117072","url":null,"abstract":"<div><div>In this paper, some applications of product singular value decomposition (PSVD) for multiple quaternion matrices are considered. A general system of coupled Sylvester-type quaternion matrix equations with <span><math><mi>n</mi></math></span> equations and <span><math><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></math></span> unknowns is considered by using PSVD for <span><math><mi>n</mi></math></span> quaternion matrices, where <span><math><mi>n</mi></math></span> is an arbitrary positive integer. Some solvability conditions and general solutions to the system are derived. The general solution to the system is also presented. Some numerical examples are given to illustrate the results of this paper. Moreover, we propose an application to the encryption and decryption of color videos using the system of coupled Sylvester-type quaternion matrix equations. The results demonstrate that the method can encrypt and decrypt video frames effectively, providing high accuracy as validated by metrics such as PSNR, SSIM, and FSIM.</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117072"},"PeriodicalIF":2.6,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Curvature-guided cartoon-texture decomposition of a color image","authors":"Jingjie Wang, Wei Wang","doi":"10.1016/j.cam.2025.117075","DOIUrl":"10.1016/j.cam.2025.117075","url":null,"abstract":"<div><div>In this paper, we propose a novel curvature-guided variational model for color image decomposition. In particular, we integrate the curvature priors into the traditional variational model to steer the evolution towards preserving curvature information, meanwhile, we incorporate saturation-value total variation to regularize the cartoon component of a color image. Additionally, we utilize the <span><math><msup><mrow><mi>L</mi></mrow><mrow><mn>1</mn></mrow></msup></math></span> norm to model the texture component in the saturation-value color space. The proposed variational model introduces an energy functional to achieve cartoon and texture decomposition in saturation-value color space, and preserves color information, fine structures/edges in the cartoon component. Theoretically, we explore the properties of the proposed model and provide a theoretical discussion about the existence of the solution. We then develop an effective and efficient algorithm to minimize the problem by utilizing the alternating direction method of multipliers. Numerical examples are presented to demonstrate that the performance of our framework competes favorably with other methods in terms of visual quality and metrics such as structure similarity (SSIM), peak signal-to-noise ratio (PSNR), quaternion structural similarity (QSSIM), S-CIELAB color metric, average local contrast (ALC), and discrete entropy (DE).</div></div>","PeriodicalId":50226,"journal":{"name":"Journal of Computational and Applied Mathematics","volume":"476 ","pages":"Article 117075"},"PeriodicalIF":2.6,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}