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We present parallel and sequential dense QR factorization algorithms that are both optimal (up to polylogarithmic factors) in the amount of communication they perform, and just as stable as Householder QR. We prove optimality by extending…

Numerical Analysis · Mathematics 2008-08-21 James Demmel , Laura Grigori , Mark Hoemmen , Julien Langou

We present parallel and sequential dense QR factorization algorithms that are both optimal (up to polylogarithmic factors) in the amount of communication they perform, and just as stable as Householder QR. Our first algorithm, Tall Skinny…

Numerical Analysis · Computer Science 2008-08-29 James Demmel , Laura Grigori , Mark Hoemmen , Julien Langou

This paper describes a new QR factorization algorithm which is especially designed for massively parallel platforms combining parallel distributed multi-core nodes. These platforms make the present and the foreseeable future of…

Distributed, Parallel, and Cluster Computing · Computer Science 2012-08-27 Jack Dongarra , Mathieu Faverge , Thomas Herault , Julien Langou , and Yves Robert

Previous studies have reported that common dense linear algebra operations do not achieve speed up by using multiple geographical sites of a computational grid. Because such operations are the building blocks of most scientific…

Distributed, Parallel, and Cluster Computing · Computer Science 2016-11-15 Emmanuel Agullo , Camille Coti , Jack Dongarra , Thomas Herault , Julien Langou

We present parallel and sequential dense QR factorization algorithms for tall and skinny matrices and general rectangular matrices that both minimize communication, and are as stable as Householder QR. The sequential and parallel algorithms…

Numerical Analysis · Mathematics 2008-09-16 James Demmel , Laura Grigori , Mark Hoemmen , Julien Langou

Numerical algorithms have two kinds of costs: arithmetic and communication, by which we mean either moving data between levels of a memory hierarchy (in the sequential case) or over a network connecting processors (in the parallel case).…

Numerical Analysis · Computer Science 2011-02-02 Grey Ballard , James Demmel , Olga Holtz , Oded Schwartz

In 1981 Hong and Kung proved a lower bound on the amount of communication needed to perform dense, matrix-multiplication using the conventional $O(n^3)$ algorithm, where the input matrices were too large to fit in the small, fast memory. In…

Computational Complexity · Computer Science 2011-09-20 Grey Ballard , James Demmel , Olga Holtz , Oded Schwartz

Nowadays, large and complex deep learning (DL) models are increasingly trained in a distributed manner across multiple worker machines, in which extensive communications between workers pose serious scaling problems. In this article, we…

Distributed, Parallel, and Cluster Computing · Computer Science 2020-11-10 Shaohuai Shi , Zhenheng Tang , Xiaowen Chu , Chengjian Liu , Wei Wang , Bo Li

This paper introduces hybrid LU-QR al- gorithms for solving dense linear systems of the form Ax = b. Throughout a matrix factorization, these al- gorithms dynamically alternate LU with local pivoting and QR elimination steps, based upon…

Numerical Analysis · Mathematics 2014-01-23 Mathieu Faverge , Julien Herrmann , Julien Langou , Bradley Lowery , Yves Robert , Jack Dongarra

Hierarchical clustering over graphs is a fundamental task in data mining and machine learning with applications in domains such as phylogenetics, social network analysis, and information retrieval. Specifically, we consider the recently…

Data Structures and Algorithms · Computer Science 2022-06-16 Arpit Agarwal , Sanjeev Khanna , Huan Li , Prathamesh Patil

We investigate iterative low-resolution message-passing algorithms for quasi-cyclic LDPC codes with horizontal and vertical layered schedules. Coarse quantization and layered scheduling are highly relevant for hardware implementations to…

Information Theory · Computer Science 2022-12-19 Philipp Mohr , Gerhard Bauch

Large language model (LLM) decoding suffers from high latency due to fragmented execution across operators and heavy reliance on off-chip memory for data exchange and reduction. This execution model limits opportunities for fusion and…

Distributed, Parallel, and Cluster Computing · Computer Science 2025-08-27 Xinhao Luo , Zihan Liu , Yangjie Zhou , Shihan Fang , Ziyu Huang , Yu Feng , Chen Zhang , Shixuan Sun , Zhenzhe Zheng , Jingwen Leng , Minyi Guo

As multicore systems continue to gain ground in the High Performance Computing world, linear algebra algorithms have to be reformulated or new algorithms have to be developed in order to take advantage of the architectural features on these…

Numerical Analysis · Mathematics 2008-08-12 Alfredo Buttari , Julien Langou , Jakub Kurzak , Jack Dongarra

We present the LU decomposition with panel rank revealing pivoting (LU_PRRP), an LU factorization algorithm based on strong rank revealing QR panel factorization. LU_PRRP is more stable than Gaussian elimination with partial pivoting…

Numerical Analysis · Computer Science 2012-08-14 Amal Khabou , James W. Demmel , Laura Grigori , Ming Gu

Bilevel optimization, crucial for hyperparameter tuning, meta-learning and reinforcement learning, remains less explored in the decentralized learning paradigm, such as decentralized federated learning (DFL). Typically, decentralized…

Machine Learning · Computer Science 2024-10-21 Min Wen , Chengchang Liu , Ahmed Abdelmoniem , Yipeng Zhou , Yuedong Xu

Many real-world problems are naturally formulated as higher-order optimization (HUBO) tasks involving dense, multi-variable interactions, which are challenging to solve with classical methods. Quantum optimization offers a promising route,…

Factorizing large matrices by QR with column pivoting (QRCP) is substantially more expensive than QR without pivoting, owing to communication costs required for pivoting decisions. In contrast, randomized QRCP (RQRCP) algorithms have proven…

Numerical Analysis · Mathematics 2018-04-17 Jianwei Xiao , Ming Gu , Julien Langou

We introduce an algorithmic framework for performing QR factorization with column pivoting (QRCP) on general matrices. The framework enables the design of practical QRCP algorithms through user-controlled choices for the core subroutines.…

Mathematical Software · Computer Science 2025-07-02 Maksim Melnichenko , Riley Murray , William Killian , James Demmel , Michael W. Mahoney , Piotr Luszczek , Mark Gates

High-level applications, such as machine learning, are evolving from simple models based on multilayer perceptrons for simple image recognition to much deeper and more complex neural networks for self-driving vehicle control systems.The…

Distributed, Parallel, and Cluster Computing · Computer Science 2020-10-12 Guixiang Ma , Yao Xiao , Theodore L. Willke , Nesreen K. Ahmed , Shahin Nazarian , Paul Bogdan

Reduction of communication and efficient partitioning are key issues for achieving scalability in hierarchical $N$-Body algorithms like FMM. In the present work, we propose four independent strategies to improve partitioning and reduce…

Distributed, Parallel, and Cluster Computing · Computer Science 2017-02-20 Mustafa Abduljabbar , George Markomanolis , Huda Ibeid , Rio Yokota , David Keyes
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