Detailed Description

Newton step strategy that applies a fixed damping factor to every update.

The accepted step is \( x_{\rm new} = x - \alpha \cdot \Delta x \), where \( \alpha \) is the damping factor (1.0 = full Newton step, no damping).

Definition at line 15 of file FixedDampingStrategy.h.

#include <FixedDampingStrategy.h>

Inheritance diagram for NumLib::FixedDampingStrategy:

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Collaboration diagram for NumLib::FixedDampingStrategy:

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Public Member Functions
	FixedDampingStrategy (double damping)
StepResult	applyStep (GlobalVector const &x, GlobalVector const &minus_delta_x, GlobalVector const &res, GlobalMatrix const &J, GlobalVector &x_new, NewtonStepContext &ctx, int iteration) override
Public Member Functions inherited from NumLib::NewtonStepStrategy
virtual void	initialize (GlobalVector const &)
void	setDampingPolicy (DampingPolicy const *policy)
virtual	~NewtonStepStrategy ()=default

Private Attributes
double	_damping

Additional Inherited Members
Protected Attributes inherited from NumLib::NewtonStepStrategy
DampingPolicy const *	_damping_policy = nullptr

Constructor & Destructor Documentation

◆ FixedDampingStrategy()

NumLib::FixedDampingStrategy::FixedDampingStrategy ( double damping )

explicit

Definition at line 11 of file FixedDampingStrategy.cpp.

                                                         : _damping(damping)
{
}

References _damping.

Member Function Documentation

◆ applyStep()

StepResult NumLib::FixedDampingStrategy::applyStep	(	GlobalVector const &	x,
		GlobalVector const &	minus_delta_x,
		GlobalVector const &	res,
		GlobalMatrix const &	J,
		GlobalVector &	x_new,
		NewtonStepContext &	ctx,
		int	iteration )

overridevirtual

Given the current solution x, the Newton direction minus_delta_x, the residual res, and the Jacobian J, compute and apply a step to x_new. The strategy is free to re-evaluate F(x) internally.

Parameters

[in]	x	current solution
[in]	minus_delta_x	full Newton step (J^{-1} r)
[in]	res	residual at x
[in]	J	Jacobian at x (may be used for curvature)
[out]	x_new	accepted new solution
[in]	ctx	equation system context for re-evaluation
[in]	iteration	current outer iteration number

Implements NumLib::NewtonStepStrategy.

Definition at line 15 of file FixedDampingStrategy.cpp.

{
    double damping = _damping;
 
    if (_damping_policy)
    {
        damping = _damping_policy->apply(minus_delta_x, x, _damping);
    }
 
    MathLib::LinAlg::axpy(x_new, -damping, minus_delta_x);
 
    return {.success = true, .step_length = damping, .x_new_is_set = true};
}

References _damping, NumLib::NewtonStepStrategy::_damping_policy, and MathLib::LinAlg::axpy().

Member Data Documentation

◆ _damping

double NumLib::FixedDampingStrategy::_damping

private

Definition at line 29 of file FixedDampingStrategy.h.

Referenced by FixedDampingStrategy(), and applyStep().

The documentation for this class was generated from the following files: