This Message Is From an External Sender
This message came from outside your organization.
Hello! I have such problem, while solving linear system and using PCFactorSetDropTolerance. As I understand this function could significantly reduce number of iterations of system of solution, but there is no iterations decreasing.I had try a lot of options for this function, but there is no result
Could you suggest me if I have some mistake, while I setting up the preconditioner?
PetscCall(KSPSetType(ksp, KSPCG));
PetscCall(KSPSetInitialGuessNonzero(ksp,PETSC_TRUE));
PetscCall(KSPSetNormType(ksp, KSP_NORM_DEFAULT));
PetscCall(KSPCGSetType(ksp, KSP_CG_SYMMETRIC));
PetscCall(KSPGetPC(ksp, &pc));
PetscCall(PCSetType(pc, PCILU));
PetscCall(PCFactorSetShiftType(pc, MAT_SHIFT_POSITIVE_DEFINITE));
PetscCall(PCFactorSetLevels(pc, 2));
PetscCall(PCFactorSetReuseOrdering(pc,PETSC_TRUE));
PetscCall(PCFactorSetDropTolerance(pc, 1.e-5, 1.e-3, 10000));
PetscCall(PCFactorSetZeroPivot(pc, 1.e-3));
PetscCall(KSPSetTolerances(ksp, 1.e-8, 1.e-8, PETSC_DEFAULT, PETSC_DEFAULT));
PetscCall(KSPSetFromOptions(ksp));
PetscCall(KSPSolve(ksp, b, x));
PetscCall(KSPGetIterationNumber(ksp, &its));
