StrangLBFGSMinimizer Class Reference
[Energy Minimizer]

Limited-memory BFGS minimizer based on the Strang recurrence. More...

#include <strangLBFGS.h>

Inheritance diagram for StrangLBFGSMinimizer:

List of all members.

Public Member Functions
Constructors and Destructors
	StrangLBFGSMinimizer ()
	Default constructor.
	StrangLBFGSMinimizer (ForceField &force_field)
	Constructor expecting a valid force field.
	StrangLBFGSMinimizer (ForceField &force_field, SnapShotManager *ssm)
	Constructor expecting a valid force field and a snapshot manager.
	StrangLBFGSMinimizer (ForceField &force_field, SnapShotManager *ssm, const Options &options)
	Constructor expecting a valid force field, a snapshot manager and options.
	StrangLBFGSMinimizer (ForceField &force_field, const Options &options)
	Constructor expecting a valid force field and options.
	StrangLBFGSMinimizer (const StrangLBFGSMinimizer &rhs)
	Copy constructor.
virtual	~StrangLBFGSMinimizer ()
	Destructor.
Assignments
const StrangLBFGSMinimizer &	operator= (const StrangLBFGSMinimizer &rhs)
	Assignment operator.
Setup methods. They do all necessary preparations.
virtual bool	specificSetup ()
	Specific setup.
Accessors
void	setMaxNumOfStoredVectPairs (Size num)
	Set the maximum number of stored vector pairs.
Size	getMaxNumOfStoredVectPairs () const
	Return the maximum number of stored vector pairs.
void	setImprovedFlag (bool flag)
	Set the improved flag.
bool	getImprovedFlag () const
	Return the improved flag.
virtual double	findStep ()
	Calculate the next step.
virtual void	updateDirection ()
	Update the stored vector pairs, either by adding a new pair or if there is no space left by replacing the oldest pair.
virtual bool	minimize (Size iterations=0, bool resume=false)
	Minimize the energy of the system.
Protected Attributes
Protected Attributes
LineSearch	line_search_
	The line search.
bool	first_iter_
	Is this an initial first iteration?
Size	number_of_atoms_
	Number of movable atoms.
Size	max_num_of_vect_pairs_
	Maximum number of stored vector pairs.
Size	curr_num_of_vect_pairs_
	Current number of stored vector pairs.
bool	improved_
	Should the improved version be used?
vector< float >	rho_
	Old and new scaling values.
vector< Vector3 >	stored_s_
	Stored former steps.
vector< Vector3 >	stored_y_
	Stored former changes in gradients.
vector< float >	work_val_
	Temporarily used memory for saving scalars associated with the stored vector pairs.
Size	index_of_free_vect_
	Index of the vector pair which will be used for saving the data of the current step (usually by replacing old data).
std::vector< Vector3 >	initial_atoms_
	Positions of movable atoms when starting an iteration.

---

Detailed Description

Limited-memory BFGS minimizer based on the Strang recurrence.

A minimizer for geometry optimization based on the limited-memory BFGS method proposed in

[1] Nocedal J.: Updating quasi-Newton matrices with limited storage. Math. Comp. 35 (1980) 773-782.

[2] Liu D.C., Nocedal J.: On the limited memory BFGS method for large scale optimization. Math. Programming 45 (1989) 503-528.

If the 'improved' option is set, ideas proposed in

[3] Mehiddin Al-Baali: Improved Hessian approximations for the limited memory BFGS method. Numerical Algorithms 22 (1999) 99-112

are adopted.

---

Constructor & Destructor Documentation

StrangLBFGSMinimizer::StrangLBFGSMinimizer (   )

Default constructor.

virtual StrangLBFGSMinimizer::~StrangLBFGSMinimizer (   )  [virtual]

Destructor.

---

Member Function Documentation

virtual double StrangLBFGSMinimizer::findStep (   )  [virtual]

Calculate the next step. First, this method updates the model. Second, it performs a line search along the calculated direction afterwards. Returns: double if the line search found an acceptable solution, otherwise -1. See also: EnergyMinimizer::findStep Reimplemented from EnergyMinimizer.

virtual bool StrangLBFGSMinimizer::minimize (  Size  iterations = 0, bool  resume = false )  [virtual]

Minimize the energy of the system. This method executes at most iterations minimization steps. If the number of iterations is not given, the number specified in the options is taken. Parameters: iterations  the maximum number of iterations resume  true to resume a previous run See also: EnergyMinimizer::minimize Reimplemented from EnergyMinimizer.

virtual void StrangLBFGSMinimizer::updateDirection (   )  [virtual]

Update the stored vector pairs, either by adding a new pair or if there is no space left by replacing the oldest pair. Compute the search direction afterwards by using the Strang recurrence formula (optional: with an improvement idea of Al-Baali). Reimplemented from EnergyMinimizer.

---

Member Data Documentation

Size StrangLBFGSMinimizer::curr_num_of_vect_pairs_ [protected]

Current number of stored vector pairs.

Size StrangLBFGSMinimizer::index_of_free_vect_ [protected]

Index of the vector pair which will be used for saving the data of the current step (usually by replacing old data).

std::vector<Vector3> StrangLBFGSMinimizer::initial_atoms_ [protected]

Positions of movable atoms when starting an iteration. This is used to reduce slightly rounding errors

Size StrangLBFGSMinimizer::max_num_of_vect_pairs_ [protected]

Maximum number of stored vector pairs.

Size StrangLBFGSMinimizer::number_of_atoms_ [protected]

Number of movable atoms.

vector<float> StrangLBFGSMinimizer::rho_ [protected]

Old and new scaling values. Also used in the Strang recurrence formula.

vector<Vector3> StrangLBFGSMinimizer::stored_s_ [protected]

Stored former steps. Vectors stored in column order.

vector<Vector3> StrangLBFGSMinimizer::stored_y_ [protected]

Stored former changes in gradients. Vectors stored in column order.

vector<float> StrangLBFGSMinimizer::work_val_ [protected]

Temporarily used memory for saving scalars associated with the stored vector pairs.