The solver doesn't converge

[Yixun Liu]

Hi,
I build a finite element system and the related PETSc codes are following,

 KSPSetOperators(ksp,sparseMechanicalStiffnessMatrix,sparseMechanicalStiffnessMatrix,DIFFERENT_NONZERO_PATTERN);
  KSPSetTolerances(ksp,0.001,1.e-50,PETSC_DEFAULT, PETSC_DEFAULT);

I output the solution and find its magnitude is about 1.0e+10. It's
definitely wrong.  The correct solution should be around 1 or 2. It
seems the solver cannot converge. How do deal with this issue?

Thanks.

Yixun