Reference documentation for deal.II version GIT defb42778c 20221205 01:15:02+00:00

#include <deal.II/lac/trilinos_precondition.h>
Public Member Functions  
AdditionalData (const unsigned int ic_fill=0, const double ic_atol=0., const double ic_rtol=1., const unsigned int overlap=0)  
Public Attributes  
unsigned int  ic_fill 
double  ic_atol 
double  ic_rtol 
unsigned int  overlap 
Standardized data struct to pipe additional parameters to the preconditioner. The Trilinos IC decomposition allows for some fillin, so it actually is a threshold incomplete Cholesky factorization. The amount of fillin, and hence, the amount of memory used by this preconditioner, is controlled by the parameter ic_fill
, which specifies this as a double. When forming the preconditioner, for certain problems bad conditioning (or just bad luck) can cause the preconditioner to be very poorly conditioned. Hence it can help to add diagonal perturbations to the original matrix and form the preconditioner for this slightly better matrix. ic_atol
is an absolute perturbation that is added to the diagonal before forming the prec, and ic_rtol
is a scaling factor \(rtol \geq 1\). The last parameter specifies the overlap of the partitions when the preconditioner runs in parallel.
Definition at line 877 of file trilinos_precondition.h.
TrilinosWrappers::PreconditionIC::AdditionalData::AdditionalData  (  const unsigned int  ic_fill = 0 , 
const double  ic_atol = 0. , 

const double  ic_rtol = 1. , 

const unsigned int  overlap = 0 

) 
Constructor. By default, set the drop tolerance to 0, the level of extra fillins is set to be zero (just use the matrix structure, do not generate any additional fillin), the tolerance level are 0 and 1, respectively, and the overlap in case of a parallel execution is zero. This overlap in a blockapplication of the IC in the parallel case makes the preconditioner a socalled additive Schwarz preconditioner.
Definition at line 452 of file trilinos_precondition.cc.
unsigned int TrilinosWrappers::PreconditionIC::AdditionalData::ic_fill 
This specifies the amount of additional fillin elements besides the sparse matrix structure. When ic_fill
is large, this means that many fillins will be added, so that the IC preconditioner comes closer to a direct sparse Cholesky decomposition. Note, however, that this will drastically increase the memory requirement, especially when the preconditioner is used in 3D.
Definition at line 901 of file trilinos_precondition.h.
double TrilinosWrappers::PreconditionIC::AdditionalData::ic_atol 
This specifies the amount of an absolute perturbation that will be added to the diagonal of the matrix, which sometimes can help to get better preconditioners.
Definition at line 908 of file trilinos_precondition.h.
double TrilinosWrappers::PreconditionIC::AdditionalData::ic_rtol 
This specifies the factor by which the diagonal of the matrix will be scaled, which sometimes can help to get better preconditioners.
Definition at line 914 of file trilinos_precondition.h.
unsigned int TrilinosWrappers::PreconditionIC::AdditionalData::overlap 
This determines how large the overlap of the local matrix portions on each processor in a parallel application should be.
Definition at line 920 of file trilinos_precondition.h.