[petsc-users] precondition for matrix-free GMRES

[RenZhengYong]

Dear petsc users,

I have a question to ask for your suggestions which is to solve Ax=b using
GMRES,
here A is partially dense.  Using petsc, I successfully used the
matrix-free approach to solve
it so that the expensive storage of A is avoided.  My question is could I
offer an matrix B
(which is sparse matrix and good approximation to A) so that the
convergence rate of
GMRES can be speed up.

Best wishes
Zhengyong


-- 
Zhengyong Ren
AUG Group, Institute of Geophysics
Department of Geosciences, ETH Zurich
NO H 47 Sonneggstrasse 5
CH-8092, Zürich, Switzerland
Tel: +41 44 633 37561
e-mail: zhengyong.ren at aug.ig.erdw.ethz.ch
Gmail: renzhengyong at gmail.com
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