[petsc-users] Solve Linear System with Field Split Preconditioner

晓峰 何 tlanyan at hotmail.com
Tue Sep 27 00:45:43 CDT 2022

Hi Barry,

A00 is formed from elliptic operator.

I tried GAMG with A00, but it was extremely slow to solve the system with field-split preconditioner(I’m not sure I did it with the right way).


On Sep 26, 2022, at 23:11, Barry Smith <bsmith at petsc.dev<mailto:bsmith at petsc.dev>> wrote:

  What is your A00 operator? ILU is almost never a good choice for large scale problems. If it is an elliptic operator that using a PC of gamg may work well for the A00 preconditioner instead of ILU.


  For moderate size problems you can use a PC type LU for AOO to help you understand the best preconditioner to use for the A11 (the Schur complement block), once you have a good preconditioner for the A11 block you would then go back and determine a good preconditioner for the A00 block.

On Sep 26, 2022, at 10:08 AM, 晓峰 何 <tlanyan at hotmail.com<mailto:tlanyan at hotmail.com>> wrote:

Hello Jed,

The saddle point is due to Lagrange multipliers, thus the size of A11 is much smaller than A00.

Best Regards,


On Sep 26, 2022, at 21:03, Jed Brown <jed at jedbrown.org<mailto:jed at jedbrown.org>> wrote:

Lagrange multipliers

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