Integrator Class Reference

Update velocities and positions. More...

#include <Integrator.h>

Inheritance diagram for Integrator:

Public Member Functions
	Integrator ()
	The constructor.
	Integrator (double timestepLength)
virtual	~Integrator ()
	The destructor.
virtual void	readXML (XMLfileUnits &xmlconfig)=0
virtual void	init ()=0
virtual void	eventForcesCalculated (ParticleContainer *moleculeContainer, Domain *domain)=0
	informs the integrator about available forces, who then continues integration More...
virtual void	eventNewTimestep (ParticleContainer *moleculeContainer, Domain *domain)=0
	inform the integrator that the integration should continue More...
void	setTimestepLength (double dt)
	set the time between two time steps
double	getTimestepLength ()
	get the time between two time steps

Protected Attributes
double	_timestepLength
	time between time step n and time step (n+1)

Detailed Description

Update velocities and positions.

Author

Martin Buchholz, Martin Bernreuther, et al.

The basic idea of the integrator is, that it calculates from given values at one timestep the corresponding values in the next timestep. A PRECONDITION for each integrator is, that all values that the integrator reads before it writes them have to be available at the same point in time (usually t=0). E.g. positions and velocities are always available at the same starting time as they are read from the input file, but the forces don't stand in the input file, so they have to be calculated for t=0 before the integrator starts working.

The idea of this interface is that different integrators can be used, but the user of the main application shouldn't have to care which integrator is used. This of course means, that there can't be a method called "second_velocity_half_step_of_leapfrog_integrator". For different integrators, different steps at different steps of the program are needed. So it isn't feasible to have methods which performs a certain step of an integrator. The "User" even might not know, which information the integrator needs to calculate a certain value. So the idea is, the the user (surrounding method) informs the integrator whenever some new information (e.g. new Forces on the molecules) is available. The integrator should then know what can be done with this new information (e.g. calculate new accelaration)

Member Function Documentation

eventForcesCalculated()

virtual void Integrator::eventForcesCalculated ( ParticleContainer *  moleculeContainer, Domain *  domain  )

pure virtual

informs the integrator about available forces, who then continues integration

An Integrator can't calculate the force on molecules. But the forces are needed to solve the equations of motion. This method informs the integrator that the forces on all molecules have been calculated (by some other module), so the integrator should continue it's work up to a point where all values are available at the time step end.

Parameters

moleculeContainer	containes the molecules for which the equations of motion shall be solved
domain	needed because some macroscopic values (Thermostat) might influence the integrator

Implemented in Leapfrog, and LeapfrogRMM.

eventNewTimestep()

virtual void Integrator::eventNewTimestep ( ParticleContainer *  moleculeContainer, Domain *  domain  )

pure virtual

inform the integrator that the integration should continue

Basically, the only point where an integrator has to interrupt it's work is when it needs forces to continue, which is not necessarily between two time steps. But the simulation program usually wants to do something (output) between two time steps (this has to be done as only then all values (x, v,...) are avaiable for the same point in time). So the integrator interrupts it's work at the end of one time step and resumes work with the call of this method.

Parameters

moleculeContainer	containes the molecules for which the equations of motion shall be solved
domain	needed because some macroscopic values (Thermostat) might influence the integrator

Implemented in Leapfrog, and LeapfrogRMM.

init()

virtual void Integrator::init ( )

pure virtual

Initialize Integrator

Implemented in Leapfrog, and LeapfrogRMM.

readXML()

virtual void Integrator::readXML ( XMLfileUnits &  xmlconfig )

pure virtual

Implemented in Leapfrog.

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

• src/integrators/Integrator.h