On 2/1/20 12:44 PM, Krishnakumar Gopalakrishnan wrote:
"_Two difficulties_ arise due to the _*zero pivots*_ in the bottom-right block
of the matrix.
1. Firstly, following a classical result from linear algebra, such matrices
are indefinite and the conjugate gradient solver cannot be applied. We
would have to resort to other iterative solvers instead, such as MinRes,
SymmLQ, or GMRES, that can deal with indefinite systems.
2. Secondly, due to the//zero block, there are zeros on the diagonal and none
of the usual, "simple" preconditioners (Jacobi, SSOR) will work as they
require division by diagonal elements"
How about this:
https://github.com/dealii/dealii/pull/9470
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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