Exploiting variable precision in GMRES

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

Research output: Working paper

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We describe how variable precision floating point arithmetic can be used in
the iterative solver GMRES. We show how the precision of the inner products
carried out in the algorithm can be reduced as the iterations proceed, without
affecting the convergence rate or final accuracy achieved by the iterates.
Our analysis explicitly takes into account the resulting loss of orthogonality
in the Arnoldi vectors. We also show how inexact matrix-vector products can
be incorporated into this setting.
Original languageEnglish
Number of pages19
Publication statusPublished - Jul 2019


  • numerical analysis
  • variable precision
  • Krylov methods
  • ilinear algebra


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