[petsc-users] -ksp_diagonal_scale

[Jed Brown]

On Fri, Dec 23, 2011 at 04:11, Alexander Grayver <agrayver at gfz-potsdam.de>wrote:

> I would also be interested more to know how it scales system? I mean what
> is idea behind this scaling.


http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/KSP/KSPSetDiagonalScale.html

It takes the inverse square root of the diagonal and does symmetric
scaling. If you used this with no additional preconditioner, it would be
like preconditioning with Jacobi. The point is to correct some ill-scaling
*before* sending the matrix to an algebraic preconditioner.
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