UPMC, Master 2 Mathematics and Applications, Fall 2019
High performance computing for numerical methods and data analysis


Syllabus | Schedule of Lectures | Recommended reading |


Syllabus, Wednesdays 9 AM - 12 PM

Instructor: L. Grigori
Location: 15/16-101 (except on October 23 when the location will be 15/16-309), Sorbonne Université, Jussieu campus


The objective of this course is to provide the necessary background for designing efficient parallel algorithms in scientific computing as well as in the analysis of large volumes of data. The operations considered are the most costly steps at the heart of many complex numerical simulations. Parallel computing aspects in the analysis of large data sets will be studied through tensor calculus in high dimension. The course will also give an introduction to the most recent algorithms in large scale numerical linear algebra, an analysis of their numerical stability, associated with a study of their complexity in terms of computation and communication.

The lecture will also discuss one of the major challenges in high performance computing which is the increased communication cost. The traditional metric for the cost of an algorithm is the number of arithmetic or logical operations it performs. But the most expensive operation an algorithm performs, measured in time or energy, is not arithmetic or logic, but communication, i.e. moving data between levels of a memory hierarchy or between processors over a network. The difference in costs can be orders of magnitude, and is growing over time due to technological trends like Moore's Law. So our goal is to design new algorithms that communicate much less than conventional algorithms, attaining lower bounds when possible.

This course will also present an overview of novel "communication-avoiding" (CA) algorithms that attain these goals, including communication lower bounds, and practical implementations showing large speedups. Problem domains considered include dense and sparse linear algebra and tensors.

> Top of the page  

Schedule of lectures

  • Oct 23
    9:00 - 10:30 Introduction to high performance computing
    10:30 - 12:00 Communication avoiding matrix multiplication, LU, QR (Part 1), slides . Suggested reading pdf , Chapter in Computational Mathematics, Numerical Analysis and Applications, SEMA SIMAI Springer Series.
  • Nov 6
    9:00 - 10:30 LU and QR factorizations, slides
    10:30 - 12:00 Communication avoiding matrix multiplication, LU, QR (Part 2, same slides as Lecture from Oct 23)
  • Nov 13
    9:00 - 10:30 Communication avoiding LU and QR factorizations (continued)
    10:30 - 12:00 Introduction to distributed memory machines and MPI
    Recommended slides Lecture 7 of J. Demmel's class
  • Nov 20
    9:00 - 10:30 Randomized algorithms for low rank matrix approximation, slides
    Project on randomized algorithms, pdf
    10:30 - 12:00 MPI hands-on (1st part, TP), this class will take place in 15-25/322
  • Nov 27
    9:00 - 10:30 Randomized algorithms for low rank matrix approximation (contd)
    10:30 - 12:00 MPI hands-on (2nd part, TP), this class will take place in 15-25/322
  • Dec 4
    9:00 - 12:00AM Deterministic algorithms for low rank matrix approximation, slides
  • Dec 11
    9:00 - 12:00 Krylov subspace methods and preconditioners, slides
  • Dec 18
    9:00 - 12:00AM Low rank tensor approximations, slides
  • Jan 8, 2020, room 15/16-101
    Final exam (only paper documents are allowed during the exam)
    Example of questions from a previous year given at the exam is here .
  • > Top of the page  

    Recommended reading (evolving)



    For communication avoiding algorithms:

    Lower bounds on communication
  • Michael Christ, James Demmel, Nicholas Knight, Thomas Scanlon, and Katherine Yelick
    Communication Lower Bounds and Optimal Algorithms for Programs That Reference Arrays — Part 1
    EECS Technical Report No. UCB/EECS-2013-61, May 14, 2013.
  • Grey Ballard, James Demmel, Olga Holtz, Oded Schwartz,
    Minimizing Communication in Numerical Linear Algebra,
    SIAM Journal on Matrix Analysis and Applications, SIAM, Volume 32, Number 3, pp. 866-901, 2011, pdf .
  • Communication avoiding algorithms for dense linear algebra
  • J. Demmel, L. Grigori, M. F. Hoemmen, and J. Langou,
    Communication-optimal parallel and sequential QR and LU factorizations,
    SIAM Journal on Scientific Computing, Vol. 34, No 1, 2012, pdf (also available on arXiv:0808.2664v1), short version of UCB-EECS-2008-89 and LAWN 204, available since 2008.
  • L. Grigori, J. Demmel, and H. Xiang,
    CALU: a communication optimal LU factorization algorithm,
    SIAM J. Matrix Anal. & Appl., 32, pp. 1317-1350, 2011, pdf preliminary version published as LAWN 226
  • J. Demmel, L. Grigori, M. Gu, and H. Xiang
    Communication avoiding rank revealing QR factorization with column pivoting, pdf,
    SIAM J. Matrix Anal. & Appl, Vol. 36, No. 1, pp. 55-89, 2015.
  • G. Ballard, J. Demmel, L. Grigori, M. Jacquelin, N. Knight, D. Nguyen
    Reconstructing Householder vectors for QR factorization ,
    Journal of Parallel and Distributed Computing, Aug 2015, pdf.
  • Communication avoiding algorithms for iterative methods and preconditioners
  • L. Grigori, S. Moufawad, F. Nataf
    Enlarged Krylov Subspace Conjugate Gradient Methods for Reducing Communication , INRIA TR 8597 ,
    to appear in SIAM J. Matrix Anal. & Appl, 2016.
  • Randomized numerical linear algebra: overview, elementary proofs, low rank approximation algorithms, sketching algorithms
  • for a list of suggested reading, please check the Reading group on randomized linear algebra, Spring 2015

  • > Top of the page  
    INRIA Paris
    Laboratoire J. L. Lions
    Sorbonne Université
    Contact: Laura Grigori (Laura(dot)Grigori(at)inria(dot)fr)

    © 2007 rs