Faunus::MetropolisMonteCarlo Class Reference

Class to handle Monte Carlo moves. More...

#include <montecarlo.h>

Classes
struct	State
	Class to describe a system state. More...

Public Member Functions
	MetropolisMonteCarlo (const json &j)
Energy::Hamiltonian &	getHamiltonian ()
	Get Hamiltonian of accepted (default) state.
Space &	getSpace ()
	Access to space in accepted (default) state.
Space &	getTrialSpace ()
	Access to trial space.
double	relativeEnergyDrift ()
	Relative energy drift from initial configuration. More...
void	sweep ()
	Perform all moves (stochastic and static) More...
void	restore (const json &j)
	Restores system from previously store json object. More...
	~MetropolisMonteCarlo ()
	Required due to unique_ptr to incomplete type.

Static Public Member Functions
static bool	metropolisCriterion (double energy_change)
	Metropolis criterion. More...

Friends
void	to_json (json &, const MetropolisMonteCarlo &)
	Write information to JSON object.

Detailed Description

Class to handle Monte Carlo moves.

This class maintains a list of MC moves and takes care of randomly selecting a move; perform the move; decides if the move is accepted; and checks if there is a drift in the potential energy.

The moves always operate on a trial state (new_state). If accepted, the changes will be copied into the old_state. The state here refers to the particle states (positions etc.), the simulation geometry (size, volume), and the state of the Hamiltonian (wave-vectors for Ewald etc.).

Todo:

The class has too many responsibilities, particularly in setting up the system.

Member Function Documentation

metropolisCriterion()

bool Faunus::MetropolisMonteCarlo::metropolisCriterion ( double  energy_change )

static

Metropolis criterion.

Parameters

energy_change

Energy change, (new minus old) in units of kT

Returns

True if accepted, false of rejected

Note

Regardless of outcome the random number generator should be incremented. This is important when using some MPI schemes where the simulations must be in sync.

relativeEnergyDrift()

double Faunus::MetropolisMonteCarlo::relativeEnergyDrift

(

)

Relative energy drift from initial configuration.

This is a powerful test that compares the final energy with the initial energy plus the accumulated list of changes.

Ideally this difference should be very small. If a MC move improperly captures the resulting energy change, a large drift will usually appear. This test has a minimal computational overhead as only the initial and final energies need to be calculated; the accumulated change is sampled during simulation for free.

Returns

Relative energy drift

restore()

void Faunus::MetropolisMonteCarlo::restore

(

const json &

j

)

Restores system from previously store json object.

Todo:

Too many responsibilities; tidy up!

sweep()

void Faunus::MetropolisMonteCarlo::sweep

(

)

Perform all moves (stochastic and static)

This "sweeps" over all registered MC moves respecting, with the probability of picking a move given by Movebase::weight.

First stochastic moves are randomly picked and, if needed, repeated (randomly). Next, static moves are performed. Currently static moves are defined by setting weight=0.

Todo:

using weight to mark as move as static is ugly

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

• src/montecarlo.h
• src/montecarlo.cpp