Preconditioner
Hi, I'm Nailya. I solve NavierStokes equations in implicit way using finite difference method on unstructured meshes, TVD method, Newton's method. The obtained linearized system I try to solve using GMRES method. The problem is that the matrix of system is very illconditioned. I need in a good preconditioner. How can I obtain it?

Re: Preconditioner
You can try to find some packages such as QMRPACK, SPARKSKIT from netlib and there are some preconditioning GMRES built in...

Re: Preconditioner
Nailya, Why is your system of equations so illconditioned? Make sure you assemble your matrix correctly. You can start trying to precondition your system of equations using a Jacobi Preconditioner.
Chuck 
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