SpECTRE
v2024.06.18

Items related to checking the convergence of numerical algorithms. More...
Namespaces  
namespace  OptionTags 
Option tags related to the convergence of iterative algorithms.  
namespace  Tags 
Tags related to the convergence of iterative algorithms.  
Classes  
struct  Criteria 
Criteria that determine an iterative algorithm has converged. More...  
struct  HasConverged 
Signals convergence or termination of the algorithm. More...  
Enumerations  
enum class  Reason { NumIterations , MaxIterations , AbsoluteResidual , RelativeResidual , Error } 
The reason the algorithm has converged or terminated. More...  
Functions  
bool  operator== (const Criteria &lhs, const Criteria &rhs) 
bool  operator!= (const Criteria &lhs, const Criteria &rhs) 
std::optional< Reason >  criteria_match (const Criteria &criteria, size_t iteration_id, double residual_magnitude, double initial_residual_magnitude) 
Determine whether the criteria are met. More...  
std::ostream &  operator<< (std::ostream &os, const Reason &reason) 
Items related to checking the convergence of numerical algorithms.

strong 
The reason the algorithm has converged or terminated.
std::optional< Reason > Convergence::criteria_match  (  const Criteria &  criteria, 
size_t  iteration_id,  
double  residual_magnitude,  
double  initial_residual_magnitude  
) 
Determine whether the criteria
are met.
iteration_id
is that of the latest completed step and that it is zeroindexed, where zero indicates the initial state of the algorithm. Therefore, the MaxIteration
criterion will match if the iteration_id
is equal or higher. For example, a MaxIteration
of 0 means the algorithm should run no iterations, so it matches if the iteration_id
is 0 or higher since that's the initial state before any steps have been performed. A MaxIteration
of 1 matches if the iteration_id
is 1 or higher since one iteration is complete. At this point, also the residual_magnitude
reflects the state of the algorithm after completion of the first iteration. The initial_residual_magnitude
always refers to the state before the first iteration has begun, i.e. where the iteration_id
is zero.Returns: A Convergence::Reason
if the criteria are met, or std::nullopt
otherwise. The possible convergence reasons are:
Convergence::Reason::AbsoluteResidual
if the residual_magnitude
meets the convergence criteria's absolute_residual
.Convergence::Reason::RelativeResidual
if residual_magnitude / initial_residual_magnitude
meets the convergence criteria's relative_residual
.Convergence::Reason::MaxIterations
if the iteration_id
is the convergence_criteria's max_iterations
or higher. This is often interpreted as an error because the algorithm did not converge in the alloted number of iterations.