petsc-master 2020-10-26
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PCFactorSetDropTolerance

The preconditioner will use an ILU based on a drop tolerance. (Under development)

Synopsis

#include "petscpc.h" 
PetscErrorCode  PCFactorSetDropTolerance(PC pc,PetscReal dt,PetscReal dtcol,PetscInt maxrowcount)
Logically Collective on PC

Input Parameters

pc - the preconditioner context
dt - the drop tolerance, try from 1.e-10 to .1
dtcol - tolerance for column pivot, good values [0.1 to 0.01]
maxrowcount - the max number of nonzeros allowed in a row, best value depends on the number of nonzeros in row of original matrix

Options Database Key

-pc_factor_drop_tolerance <dt,dtcol,maxrowcount> - Sets drop tolerance

There are NO default values for the 3 parameters, you must set them with reasonable values for your matrix. We don't know how to compute reasonable values.

Level

intermediate

Location

src/ksp/pc/impls/factor/factor.c

Implementations

PCFactorSetDropTolerance_Factor in src/ksp/pc/impls/factor/factimpl.c
PCFactorSetDropTolerance_ILU in src/ksp/pc/impls/factor/ilu/ilu.c

Index of all PC routines
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Index of all manual pages