VTS_Control Class Reference

Provides variable time stepping control together with the logging at equidistant time intervals. More...

#include <vts.h>

Public Types
enum	ROLLBACK_MODE
	sets the criteria for energy conservation at each step ROLLBACK_ON_DE_DT the value of (E1-E0)/dt is preserved ROLLBACK_ON_DE the value of (E1-E0) is preserved

Public Member Functions
	VTS_Control (VTS_METHOD vts_method=VTS_NONE, STEP_ALGORITHM step_algorithm=STEP_MD)
	Constructor. See init for explanation.
void	init (VTS_METHOD vts_method=VTS_NONE, STEP_ALGORITHM step_algorithm=STEP_MD)
	Sets the VTS method, basic stepping algorithm and initializes all public variables.
void	set_max_drift (double en_drift_max=0.)
	Sets the maximal value of energy change at which the rollback is requested.
bool	test_step (double dt, double en_drift, double *dt_new=0, double time_to_update=0., bool invalid_state=false)
	Returns true if a step made from t to t+dt is acceptable with the given energy drift en_drift.

Public Attributes
double	en_drift_goal
	desired average energy drift
double	en_drift_low
	additional parameters for VTS_EPSILONS method: if en_drift_low < en_drift < en_drift_goal the timestep is unchnaged
double	dt_raise
	maximal timestep increasing factor for a single step
double	dt_descent
	timestep decreasing fator for VTS_SIMPLE and VTS_EPSILONS methods
double	exponent
	exponent for VTS_PREDICTIVE method: dE ~ pow(dt,exp)
double	dt_low_limit
	lowest allowed timestep, ignored if zero
double	dt_upper_limit
	highest allowed timestep, ignored if zero
double	dt_critical
	lowest step to autoswitch to ROLLBACK_ON_DE, ignored if zero
int	forwards
	number of accepted steps
int	rollbacks
	number of rollbacks
int	low_limit_reached
	number of approaching the lowest timestep

Detailed Description

Provides variable time stepping control together with the logging at equidistant time intervals.

Member Function Documentation

init()

void VTS_Control::init	(	VTS_METHOD	vts_method = VTS_NONE,
		STEP_ALGORITHM	step_algorithm = STEP_MD
	)

Sets the VTS method, basic stepping algorithm and initializes all public variables.

Parameters

vts_method	Timestep control method
step_algorithm	Global algorithm: MD or minimization

test_step()

bool VTS_Control::test_step	(	double	dt,
		double	en_drift,
		double *	dt_new = 0,
		double	time_to_update = 0.,
		bool	invalid_state = false
	)

Returns true if a step made from t to t+dt is acceptable with the given energy drift en_drift.

In case of ACCEPTED step puts the suggested (possibly increased) NEXT time step (to be used for stepping further from (t+dt) to (t+dt)+dt_new) into dt_new. If time_to_update > 0, then dt_new is set to be lower or equal time_to_update. Used to match the time moments for log file updates. In case of REJECTED step puts the suggested CORRECTED (reduced) time step (to be used for repeating a step from t to t+dt_new) into dt_corrected. This value should be used for the next trial (revert to time t, make step to t+dt_new, evaluate en_drift again).

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

• vts.h