A NOTE ON INEXACT INNER PRODUCTS IN GMRES

Serge Gratton, Ehouarn Simon, David Titley-Peloquin, Philippe L. Toint

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We show to what extent the accuracy of the inner products computed in the GMRES iterative solver can be reduced as the iterations proceed without affecting the convergence rate or final accuracy achieved by the iterates. We bound the loss of orthogonality in GMRES with inexact inner products. We use this result to bound the ratio of the residual norm in inexact GMRES to the residual norm in exact GMRES and give a condition under which this ratio remains close to 1. We illustrate our results with examples in variable floating-point arithmetic.

    Original languageEnglish
    Pages (from-to)1406-1422
    Number of pages17
    JournalSIAM Journal on Matrix Analysis and Applications
    Volume43
    Issue number3
    DOIs
    Publication statusPublished - 2022

    Keywords

    • Arnoldi algorithm
    • GMRES algorithm
    • inexact inner products
    • variable precision arithmetic

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