# Force Class Reference

Force objects apply forces to the particles in a System, or alter their behavior in other ways. More...

`#include <Force.h>`

Inheritance diagram for Force:

List of all members.

## Public Member Functions
| Force ()
virtual | ~Force ()
int | getForceGroup () const
| Get the force group this Force belongs to.
void | setForceGroup (int group)
| Set the force group this Force belongs to.
## Protected Member Functions
virtual ForceImpl * | createImpl () const =0
| When a Context is created, it invokes this method on each Force in the System.
ForceImpl & | getImplInContext (Context &context)
| Get the ForceImpl corresponding to this Force in a Context.
ContextImpl & | getContextImpl (Context &context)
| Get the ContextImpl corresponding to a Context.
## Friends
class | ContextImpl

## Detailed Description

Force objects apply forces to the particles in a System, or alter their behavior in other ways.

This is an abstract class. Subclasses define particular forces.

More specifically, a Force object can do any or all of the following:

- Add a contribution to the force on each particle
- Add a contribution to the potential energy of the System
- Modify the positions and velocities of particles at the start of each time step
- Define parameters which are stored in the Context and can be modified by the user
- Change the values of parameters defined by other Force objects at the start of each time step

Forces may be organized into "force groups". This is used for multiple time step integration, and allows subsets of the Forces in a System to be evaluated at different times. By default, all Forces are in group 0. Call setForceGroup() to change this. Some Force subclasses may provide additional methods to further split their computations into multiple groups. Be aware that particular Platforms may place restrictions on the use of force groups, such as requiring all nonbonded forces to be in the same group.

## Constructor & Destructor Documentation

Force | ( |  | ) | `[inline]`

virtual ~Force | ( |  | ) | `[inline, virtual]`

## Member Function Documentation

virtual ForceImpl* createImpl | ( |  | ) | const`[protected, pure virtual]`

When a Context is created, it invokes this method on each Force in the System.

It should create a new ForceImpl object which can be used by the context for calculating forces. The ForceImpl will be deleted automatically when the Context is deleted.

Implemented in AndersenThermostat, CMAPTorsionForce, CMMotionRemover, CustomAngleForce, CustomBondForce, CustomCompoundBondForce, CustomExternalForce, CustomGBForce, CustomHbondForce, CustomManyParticleForce, CustomNonbondedForce, CustomTorsionForce, GBSAOBCForce, GBVIForce, HarmonicAngleForce, HarmonicBondForce, MonteCarloAnisotropicBarostat, MonteCarloBarostat, MonteCarloMembraneBarostat, NonbondedForce, PeriodicTorsionForce, RBTorsionForce, DrudeForce, AmoebaAngleForce, AmoebaBondForce, AmoebaGeneralizedKirkwoodForce, AmoebaInPlaneAngleForce, AmoebaMultipoleForce, AmoebaOutOfPlaneBendForce, AmoebaPiTorsionForce, AmoebaStretchBendForce, AmoebaTorsionTorsionForce, AmoebaVdwForce, and AmoebaWcaDispersionForce.

ContextImpl& getContextImpl | ( | Context & | context | ) | `[protected]`

Get the ContextImpl corresponding to a Context.

int getForceGroup | ( |  | ) | const

Get the force group this Force belongs to.

ForceImpl& getImplInContext | ( | Context & | context | ) | `[protected]`

Get the ForceImpl corresponding to this Force in a Context.

void setForceGroup | ( | int | group | ) |

Set the force group this Force belongs to.

Parameters:

  | group | the group index. Legal values are between 0 and 31 (inclusive).

## Friends And Related Function Documentation

friend class ContextImpl`[friend]`

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

- Force.h