# State Class Reference

A State object records a snapshot of the current state of a simulation at a point in time. More...

`#include <State.h>`

List of all members.

## Public Types
enum | DataType { Positions = 1, Velocities = 2, Forces = 4, Energy = 8, Parameters = 16 }
| This is an enumeration of the types of data which may be stored in a State. More...
## Public Member Functions
| State ()
| Construct an empty State containing no data.
double | getTime () const
| Get the time for which this State was created.
const std::vector< Vec3 > & | getPositions () const
| Get the position of each particle.
const std::vector< Vec3 > & | getVelocities () const
| Get the velocity of each particle.
const std::vector< Vec3 > & | getForces () const
| Get the force acting on each particle.
double | getKineticEnergy () const
| Get the total kinetic energy of the system.
double | getPotentialEnergy () const
| Get the total potential energy of the system.
void | getPeriodicBoxVectors (Vec3 &a, Vec3 &b, Vec3 &c) const
| Get the vectors defining the axes of the periodic box (measured in nm).
double | getPeriodicBoxVolume () const
| Get the volume of the periodic box (measured in nm^3).
const std::map< std::string, double > & | getParameters () const
| Get a map containing the values of all parameters.
| StateBuilder (double time)
State | getState ()
void | setPositions (const std::vector< Vec3 > &pos)
void | setVelocities (const std::vector< Vec3 > &vel)
void | setForces (const std::vector< Vec3 > &force)
void | setParameters (const std::map< std::string, double > &params)
void | setEnergy (double ke, double pe)
void | setPeriodicBoxVectors (const Vec3 &a, const Vec3 &b, const Vec3 &c)

## Detailed Description

A State object records a snapshot of the current state of a simulation at a point in time.

Internal class used to construct new State objects.

You create it by calling getState() on a Context.

When a State is created, you specify what information should be stored in it. This saves time and memory by only copying in the information that you actually want. This is especially important for forces and energies, since they may need to be calculated. If you query a State object for a piece of information which is not available (because it was not requested when the State was created), it will throw an exception.

## Member Enumeration Documentation

enum DataType

This is an enumeration of the types of data which may be stored in a State.

When you create a State, use these values to specify which data types it should contain.

Enumerator:

  Positions |
  Velocities |
  Forces |
  Energy |
  Parameters |

## Constructor & Destructor Documentation

State | ( |  | ) |

Construct an empty State containing no data.

This exists so State objects can be used in STL containers.

## Member Function Documentation

const std::vector<Vec3>& getForces | ( |  | ) | const

Get the force acting on each particle.

If this State does not contain forces, this will throw an exception.

double getKineticEnergy | ( |  | ) | const

Get the total kinetic energy of the system.

If this State does not contain energies, this will throw an exception.

Note that this may be different from simply mv2/2 summed over all particles. For example, a leapfrog integrator will store velocities offset by half a step, so they must be adjusted before computing the kinetic energy. This routine returns the kinetic energy at the current time, computed in a way that is appropriate for whatever Integrator is being used.

const std::map<std::string, double>& getParameters | ( |  | ) | const

Get a map containing the values of all parameters.

If this State does not contain parameters, this will throw an exception.

void getPeriodicBoxVectors | ( | Vec3 & | a,
|  | Vec3 & | b,
|  | Vec3 & | c |
| ) |  |  | const

Get the vectors defining the axes of the periodic box (measured in nm).

Parameters:

  | a | on exit, this contains the vector defining the first edge of the periodic box
  | b | on exit, this contains the vector defining the second edge of the periodic box
  | c | on exit, this contains the vector defining the third edge of the periodic box

double getPeriodicBoxVolume | ( |  | ) | const

Get the volume of the periodic box (measured in nm^3).

const std::vector<Vec3>& getPositions | ( |  | ) | const

Get the position of each particle.

If this State does not contain positions, this will throw an exception.

double getPotentialEnergy | ( |  | ) | const

Get the total potential energy of the system.

If this State does not contain energies, this will throw an exception.

State getState | ( |  | ) |

double getTime | ( |  | ) | const

Get the time for which this State was created.

const std::vector<Vec3>& getVelocities | ( |  | ) | const

Get the velocity of each particle.

If this State does not contain velocities, this will throw an exception.

void setEnergy | ( | double | ke,
|  | double | pe |
| ) |  |  |

void setForces | ( | const std::vector< Vec3 > & | force | ) |

void setParameters | ( | const std::map< std::string, double > & | params | ) |

void setPeriodicBoxVectors | ( | const Vec3 & | a,
|  | const Vec3 & | b,
|  | const Vec3 & | c |
| ) |  |  |

void setPositions | ( | const std::vector< Vec3 > & | pos | ) |

void setVelocities | ( | const std::vector< Vec3 > & | vel | ) |

StateBuilder | ( | double | time | ) |

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

- State.h