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Public Member Functions | Protected Member Functions | Protected Attributes
BootstrapFilter< StateVar, MeasVar > Class Template Reference

Particular particle filter : Proposal PDF = SystemPDF. More...

#include <bootstrapfilter.h>

Inheritance diagram for BootstrapFilter< StateVar, MeasVar >:
ParticleFilter< StateVar, MeasVar > Filter< StateVar, MeasVar >

List of all members.

Public Member Functions

 BootstrapFilter (MCPdf< StateVar > *prior, int resampleperiod=0, double resamplethreshold=0, int resamplescheme=DEFAULT_RS)
 Constructor.
 BootstrapFilter (MCPdf< StateVar > *prior, MCPdf< StateVar > *post, int resampleperiod=0, double resamplethreshold=0, int resamplescheme=DEFAULT_RS)
 Constructor.
virtual ~BootstrapFilter ()
 Destructor.
virtual void ProposalSet (ConditionalPdf< StateVar, StateVar > *const cpdf)
 Set the proposal density.
ConditionalPdf< StateVar,
StateVar > * 
ProposalGet ()
 Get a pointer to the proposal density.
virtual MCPdf< StateVar > * PostGet ()
 Get Posterior density.
virtual void Reset (Pdf< StateVar > *prior)
 Reset Filter.
virtual bool Update (SystemModel< StateVar > *const sysmodel, const StateVar &u, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z, const StateVar &s)
 Full Update (system with inputs/sensing params)
virtual bool Update (SystemModel< StateVar > *const sysmodel, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z, const StateVar &s)
 Full Update (system without inputs, with sensing params)
virtual bool Update (SystemModel< StateVar > *const sysmodel, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z)
 Full Update (system without inputs/sensing params)
virtual bool Update (SystemModel< StateVar > *const sysmodel, const StateVar &u, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z)
 Full Update (system with inputs, without sensing params)
virtual bool Update (SystemModel< StateVar > *const sysmodel, const StateVar &u)
 System Update (system with inputs)
virtual bool Update (SystemModel< StateVar > *const sysmodel)
 System Update (system without inputs)
virtual bool Update (MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z, const StateVar &s)
 Measurement Update (system with "sensing params")
virtual bool Update (MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z)
 Measurement Update (system without "sensing params")
int TimeStepGet () const
 Get current time.

Protected Member Functions

virtual bool UpdateInternal (SystemModel< StateVar > *const sysmodel, const StateVar &u, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z, const StateVar &s)
 Actual implementation of updateinternal.
virtual bool ProposalStepInternal (SystemModel< StateVar > *const sysmodel, const StateVar &u, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z, const StateVar &s)
 Proposal step.
virtual bool UpdateWeightsInternal (SystemModel< StateVar > *const sysmodel, const StateVar &u, MeasurementModel< MeasVar, StateVar > *const measmodel, const MeasVar &z, const StateVar &s)
 Update Weights.
virtual bool DynamicResampleStep ()
 Resample if necessary.
virtual bool StaticResampleStep ()
 Resample if wanted.
virtual bool Resample ()
 Actual Resampling happens here;.

Protected Attributes

ConditionalPdf< StateVar,
StateVar > * 
_proposal
 Pointer to the Proposal Density.
WeightedSample< StateVar > _sample
 While updating use sample<StateVar>
vector< WeightedSample
< StateVar > > 
_old_samples
 While updating store list of old samples.
vector< WeightedSample
< StateVar > > 
_new_samples
 While updating store list of new samples.
vector< Sample< StateVar > > _new_samples_unweighted
 While resampling.
vector< WeightedSample
< StateVar > >::iterator 
_os_it
 Iterator for old list of samples.
vector< WeightedSample
< StateVar > >::iterator 
_ns_it
 Iterator for new list of samples.
int _resamplePeriod
 Number of timestep between resampling from the Posterior Pdf.
double _resampleThreshold
 Threshold used when dynamic resampling.
int _resampleScheme
 Which resample algorithm (see top of particle.h for #defines)
bool _dynamicResampling
 Dynamic resampling or fixed period resampling?
bool _proposal_depends_on_meas
 Proposal depends on last measurement?
bool _created_post
 created own post
Pdf< StateVar > * _prior
 prior Pdf
Pdf< StateVar > * _post
 Pointer to the Posterior Pdf.
int _timestep
 Represents the current timestep of the filter.

Detailed Description

template<typename StateVar, typename MeasVar>
class BFL::BootstrapFilter< StateVar, MeasVar >

Particular particle filter : Proposal PDF = SystemPDF.

This is one (simple) particular implementation of a particle filter, in which the proposal density is equal to the pdf describing the system model (aka as SystemPdf), and involving a resampling step

The reason why I chose the name bootstrap filter is the fact that this is the name used in the book by Doucet et al.

    @Book{		  doucet_book,
    editor	= {Doucet, Arnaud and de Freytas, Nando and Gordon, Neil},
    title		= {{S}equential {M}onte {C}arlo {M}ethods in {P}ractice},
    publisher	= {Springer--Verlag},
    year		= {2001},
    series	= {Statistics for engineering and information science},
    month		= {january},
    annote	= {see http://www-sigproc.eng.cam.ac.uk/~ad2/book.html}
    }
    

(and I presume this will become a/the standard book about particle filtering). Typical for the bootstrap filter is the fact that the proposal density is chosen to be the SystemPdf of the SystemModel. So there is no proposal density in the constructor here

Todo:
The implementation is very slow for the moment. It would probably be much faster to add a vector<WeightedSample> to the private members of this class.
See also:
Pdf

Definition at line 71 of file bootstrapfilter.h.


Constructor & Destructor Documentation

BootstrapFilter ( MCPdf< StateVar > *  prior,
int  resampleperiod = 0,
double  resamplethreshold = 0,
int  resamplescheme = DEFAULT_RS 
)

Constructor.

Precondition:
you created the necessary models and the prior
Parameters:
priorpointer to the Monte Carlo Pdf prior density
resampleperiodfixed resampling period (if desired)
resamplethresholdthreshold used when dynamic resampling
resampleschemeresampling scheme, see header file for different defines and their meaning
BootstrapFilter ( MCPdf< StateVar > *  prior,
MCPdf< StateVar > *  post,
int  resampleperiod = 0,
double  resamplethreshold = 0,
int  resamplescheme = DEFAULT_RS 
)

Constructor.

Precondition:
you created the necessary models and the prior
Parameters:
priorpointer to the Monte Carlo Pdf prior density
postpointer to the Monte Carlo Pdf post density
resampleperiodfixed resampling period (if desired)
resamplethresholdthreshold used when dynamic resampling
resampleschemeresampling scheme, see header file for different defines and their meaning

Member Function Documentation

bool DynamicResampleStep ( ) [protected, virtual, inherited]

Resample if necessary.

Bug:
let the user implement her/his own resamplescheme

Definition at line 272 of file particlefilter.h.

MCPdf< SV > * PostGet ( ) [virtual, inherited]

Get Posterior density.

Get the current Posterior density

Returns:
a pointer to the current posterior

Reimplemented from Filter< StateVar, MeasVar >.

Definition at line 390 of file particlefilter.h.

ConditionalPdf< SV, SV > * ProposalGet ( ) [inherited]

Get a pointer to the proposal density.

Returns:
a pointer to the proposal density

Definition at line 139 of file particlefilter.h.

void ProposalSet ( ConditionalPdf< SV, SV > *const  cpdf) [virtual, inherited]

Set the proposal density.

Parameters:
cpdfthe new proposal density. The order of the conditional arguments is fixed and should be: x (state), u (input), z (measurement), s (sensor param). Off course all of them are optional

Definition at line 133 of file particlefilter.h.

bool ProposalStepInternal ( SystemModel< SV > *const  sysmodel,
const SV &  u,
MeasurementModel< MV, SV > *const  measmodel,
const MV &  z,
const SV &  s 
) [protected, virtual, inherited]

Proposal step.

Implementation of proposal step

Parameters:
sysmodelpointer to the used system model
uinput param for proposal density
measmodelpointer to the used measurementmodel
zmeasurement param for proposal density
ssensor param for proposal density
Bug:
Make sampling method variable. See implementation.

Reimplemented in EKParticleFilter.

Definition at line 145 of file particlefilter.h.

bool StaticResampleStep ( ) [protected, virtual, inherited]

Resample if wanted.

Bug:
let the user implement her/his own resamplescheme

Definition at line 308 of file particlefilter.h.

int TimeStepGet ( ) const [inherited]

Get current time.

Get the current time of the filter

Returns:
the current timestep

Definition at line 50 of file filter.h.

bool Update ( SystemModel< SVar > *const  sysmodel,
const SVar &  u,
MeasurementModel< MVar, SVar > *const  measmodel,
const MVar &  z,
const SVar &  s 
) [virtual, inherited]

Full Update (system with inputs/sensing params)

Parameters:
sysmodelpointer to the system model to use for update
uinput to the system
measmodelpointer to the measurement model to use for update
zmeasurement
s"sensing parameter"

Definition at line 56 of file filter.h.

bool Update ( SystemModel< SVar > *const  sysmodel,
MeasurementModel< MVar, SVar > *const  measmodel,
const MVar &  z,
const SVar &  s 
) [virtual, inherited]

Full Update (system without inputs, with sensing params)

Parameters:
sysmodelpointer to the system model to use for update
measmodelpointer to the measurement model to use for update
zmeasurement
s"sensing parameter"

Definition at line 66 of file filter.h.

bool Update ( SystemModel< SVar > *const  sysmodel,
MeasurementModel< MVar, SVar > *const  measmodel,
const MVar &  z 
) [virtual, inherited]

Full Update (system without inputs/sensing params)

Parameters:
sysmodelpointer to the system model to use for update
measmodelpointer to the measurement model to use for update
zmeasurement

Definition at line 76 of file filter.h.

bool Update ( SystemModel< SVar > *const  sysmodel,
const SVar &  u,
MeasurementModel< MVar, SVar > *const  measmodel,
const MVar &  z 
) [virtual, inherited]

Full Update (system with inputs, without sensing params)

Parameters:
sysmodelpointer to the system model to use for update
uinput to the system
measmodelpointer to the measurement model to use for update
zmeasurement

Definition at line 85 of file filter.h.

bool Update ( SystemModel< SVar > *const  sysmodel,
const SVar &  u 
) [virtual, inherited]

System Update (system with inputs)

Parameters:
sysmodelpointer to the system model to use for update
uinput to the system

Definition at line 95 of file filter.h.

bool Update ( SystemModel< SVar > *const  sysmodel) [virtual, inherited]

System Update (system without inputs)

Parameters:
sysmodelpointer to the system model to use for update

Definition at line 103 of file filter.h.

bool Update ( MeasurementModel< MVar, SVar > *const  measmodel,
const MVar &  z,
const SVar &  s 
) [virtual, inherited]

Measurement Update (system with "sensing params")

Parameters:
measmodelpointer to the measurement model to use for update
zmeasurement
s"sensing parameter"

Definition at line 110 of file filter.h.

bool Update ( MeasurementModel< MVar, SVar > *const  measmodel,
const MVar &  z 
) [virtual, inherited]

Measurement Update (system without "sensing params")

Parameters:
measmodelpointer to the measurement model to use for update
zmeasurement

Definition at line 119 of file filter.h.

bool UpdateWeightsInternal ( SystemModel< SV > *const  sysmodel,
const SV &  u,
MeasurementModel< MV, SV > *const  measmodel,
const MV &  z,
const SV &  s 
) [protected, virtual, inherited]

Update Weights.

Parameters:
sysmodelpointer to the used system model
uinput param for proposal density
measmodelpointer to the used measurementmodel
zmeasurement param for proposal density
ssensor param for proposal density

Definition at line 201 of file particlefilter.h.


Member Data Documentation

Pdf<StateVar>* _post [protected, inherited]

Pointer to the Posterior Pdf.

The Posterior Pdf represents the subjective belief of the person applying the filter AFTER processing inputs and measurements. A filter does not maintain the beliefs at all timesteps t, since this leads to non-constant (or ever growing if you prefer) memory requirements. However, it is possible, to copy the Posterior density at all timesteps in your application by means of the PostGet() member function

See also:
PostGet()

Definition at line 95 of file filter.h.

ConditionalPdf<StateVar,StateVar>* _proposal [protected, inherited]

Pointer to the Proposal Density.

Every particle filter (or more correct: every Sequential Importance Sampling method) uses a proposal density to do the forward sampling step

Definition at line 174 of file particlefilter.h.

int _resamplePeriod [protected, inherited]

Number of timestep between resampling from the Posterior Pdf.

By choosing this period, one can avoid numerical instability (aka Degeneration of the particle filter

Definition at line 193 of file particlefilter.h.

int _timestep [protected, inherited]

Represents the current timestep of the filter.

Todo:
Check wether this really belongs here

Definition at line 100 of file filter.h.


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