Efficient Preconditioner Updates for Shifted Linear Systems

  • Authors:
  • Stefania Bellavia;Valentina De Simone;Daniela di Serafino;Benedetta Morini

  • Affiliations:
  • stefania.bellavia@unifi.it and benedetta.morini@unifi.it;valentina.desimone@unina2.it;daniela.diserafino@unina2.it;-

  • Venue:
  • SIAM Journal on Scientific Computing
  • Year:
  • 2011

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Abstract

We present a technique for building effective and low cost preconditioners for sequences of shifted linear systems $(A + \alpha I) x_\alpha = b$, where $A$ is symmetric positive definite and $\alpha 0$. This technique updates a preconditioner for $A$, available in the form of an $LDL^T$ factorization, by modifying only the nonzero entries of the $L$ factor in such a way that the resulting preconditioner mimics the diagonal of the shifted matrix and reproduces its overall behavior. This approach is supported by a theoretical analysis as well as by numerical experiments, showing that it works efficiently for a broad range of values of $\alpha$.