AdvanceTailMove Class Reference

A derived class which performs an advance tail move, causing the tail of a worm in a off-diagonal configuration to advance in imaginary time, resulting in a shorter worm. More...

#include <move.h>

Inheritance diagram for AdvanceTailMove:

Collaboration diagram for AdvanceTailMove:

Public Member Functions
	AdvanceTailMove (Path &, ActionBase *, MTRand &, ensemble _operateOnConfig=OFFDIAGONAL, bool _varLength=true)
	Constructor.
	~AdvanceTailMove ()
	Destructor.
bool	attemptMove ()
	Perform an advance tail move. More...
string	getName ()
	return the move name
Public Member Functions inherited from MoveBase
	MoveBase (Path &, ActionBase *, MTRand &, ensemble _operateOnConfig=ANY, bool _varLength=false)
	Move naming conventions: More...
virtual	~MoveBase ()
	Destructor.
double	getAcceptanceRatio ()
	Get the acceptance ratio.
double	getTotAcceptanceRatio ()
	Get the total acceptance ratio.
double	getAcceptanceRatioLevel (int n)
	Get the acceptance ratio by level.
int	getNumAttempted ()
	Get the number of moves attempted.
int	getNumAccepted ()
	Get the number of moves accepted.
int	getNumAttemptedLevel (int n)
	Get the number of moves attempted by level.
int	getNumAcceptedLevel (int n)
	Get the number of moves accepted by level.
void	resetTotAccept ()
	Reset the total accepted counter.
void	resetAccept ()
	Reset the number accepted counter.

Static Public Attributes
static const string	name

Additional Inherited Members
Data Fields inherited from MoveBase
ensemble	operateOnConfig
	What configurations do we operate on?
bool	variableLength
	Does the move have a variable length?
string	name1
Protected Member Functions inherited from MoveBase
dVec	newStagingPosition (const beadLocator &, const beadLocator &, const int, const int)
	Returns a new staging position which will exactly sample the kinetic action. More...
dVec	newStagingPosition (const beadLocator &, const beadLocator &, const int, const int, iVec &)
	Returns a new staging position which will exactly sample the kinetic action in different winding sectors. More...
iVec	sampleWindingSector (const beadLocator &, const beadLocator &, const int, double &)
	Obtain a winding sector for a stage-like move. More...
iVec	getWindingNumber (const beadLocator &, const beadLocator &)
	Find the winding number for a path between two beads. More...
dVec	newFreeParticlePosition (const beadLocator &)
	Generates a new position, which exactly samples the free particle density matrix. More...
dVec	newBisectionPosition (const beadLocator &, const int)
	Returns a new bisection position which will exactly sample the kinetic action. More...
void	printMoveState (string)
void	checkMove (int, double)
Protected Attributes inherited from MoveBase
Path &	path
	A reference to the paths.
ActionBase *	actionPtr
	A base pointer to the action.
MTRand &	random
	A reference to the RNG.
bool	success
	Did we sucessfully perform a move?
uint32	numAccepted
	The number of accepted moves.
uint32	numAttempted
	The number of attempted moves.
int	numToMove
	The number of particles moved.
int	numLevels
Array< uint32, 1 >	numAcceptedLevel
	The number of moves accepted at each level.
Array< uint32, 1 >	numAttemptedLevel
	The number of moves attempted at each level.
Array< dVec, 1 >	originalPos
	The original particle positions.
Array< dVec, 1 >	newPos
	New particle positions.
vector< iVec >	winding
	The winding vectors
vector< int >	windingSector
	Used to index different winding sectors.
vector< double >	cumrho0
	Used for tower-sampling winding sectors.
int	maxWind
	The largest winding number.
int	numWind
	The total number of winding vectors.
double	oldAction
	The original potential action.
double	newAction
	The new potential action.
double	deltaAction
	The action difference.
double	sqrt2LambdaTau
	sqrt(2 * Lambda * tau)
double	sqrtLambdaTau
	sqrt(Lambda * tau)
beadLocator	nBeadIndex
	Neighbor bead index.
dVec	neighborPos
	Staging neighbor position.
dVec	newRanPos
	Staing random position.
double	newK
double	oldK
	The old and new kinetic action.
double	newV
double	oldV
	The old and new potential action.
Static Protected Attributes inherited from MoveBase
static uint32	totAccepted = 0
	The total number of moves accepted.
static uint32	totAttempted = 0
	The total number of moves attempted.

Detailed Description

A derived class which performs an advance tail move, causing the tail of a worm in a off-diagonal configuration to advance in imaginary time, resulting in a shorter worm.

Definition at line 472 of file move.h.

Member Function Documentation

attemptMove()

bool AdvanceTailMove::attemptMove ( )

virtual

Perform an advance tail move.

Here we attempt to advance the tail of a worm in imaginary time by a random number of slices. This is accomplished by removing beads and the result is a shorter worm. It is only possible if we already have an off-diagonal configuration.

Implements MoveBase.

Definition at line 2609 of file move.cpp.

                                  {
 
    success = false;
 
    /* Only perform a move if we have beads */
    if (path.worm.getNumBeadsOn() == 0) 
        return success;
 
    /* Get the number of time slices we will try to shrink the worm by */
    advanceLength = 2*(1 + random.randInt(constants()->Mbar()/2-1));
    numLevels = int (ceil(log(1.0*advanceLength) / log(2.0)-EPS));
 
    /* We now make sure that this is shorter than the length of the worm, 
     * otherewise we reject the move immediatly */
    if (advanceLength < path.worm.length) {
 
        /* The proposed new tail */
        tailBead = path.next(path.worm.tail,advanceLength);
 
        /* The action shift due to the chemical potential */
        double muShift = advanceLength*constants()->tau()*constants()->mu();
 
        double norm = constants()->attemptProb("recede tail") / 
            constants()->attemptProb("advance tail");
 
        /* Weight for ensemble */
        norm *= actionPtr->ensembleWeight(-advanceLength);
 
        checkMove(0,0.0);
 
        /* Increment the number of recede moves and the total number of moves */
        numAttempted++;
        numAttemptedLevel(numLevels)++;
        totAttempted++;
 
        /* Mark the proposed tail as special */
        path.worm.special1 = tailBead;
 
        /* If we have a local action, perform a single slice rejection move */
        if (actionPtr->local) {
 
            double actionShift = (-log(norm) + muShift)/advanceLength;
 
            deltaAction = 0.0;
            double factor = 0.5;
 
            beadLocator beadIndex;
            beadIndex = path.worm.tail;
            do {
                deltaAction = -(actionPtr->barePotentialAction(beadIndex) - factor*actionShift);
 
                /* We do a single slice Metropolis test and exit the move if we
                 * wouldn't remove the single bead */
                if ( random.rand() >= exp(-deltaAction) ) {
                    undoMove();
                    return success;
                }
 
                factor = 1.0; 
                beadIndex = path.next(beadIndex);
            } while (!all(beadIndex==tailBead));
 
            /* Add the part from the tail */
            deltaAction = -(actionPtr->barePotentialAction(beadIndex) - 0.5*actionShift);
            deltaAction -= actionPtr->potentialActionCorrection(path.worm.tail,tailBead);
 
            /* Perform final metropolis test */
            if ( random.rand() < (exp(-deltaAction)) ) {
                keepMove();
                checkMove(1,deltaAction - advanceLength*actionShift);
            }
            else {
                undoMove();
                checkMove(2,0.0);
            }
        }
        /* Otherwise, perform a full trajectory update */
        else {
            /* Compute the old action for the path to be removed */
            oldAction = actionPtr->potentialAction(path.worm.tail,tailBead);
 
            /* Perform the metropolis test */
            if ( random.rand() < norm*exp(oldAction - muShift) )  {
                keepMove();
                checkMove(1,-oldAction);
            }
            else {
                undoMove();
                checkMove(2,0.0);
            }
        }
 
    } // advanceLength
 
    return success;
}

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

• include/move.h
• src/move.cpp