LHAPDF: LHAPDF::PDF Class Reference

PDF is the general interface for access to parton density information. More...

#include <PDF.h>

Inheritance diagram for LHAPDF::PDF:

Public Member Functions
virtual	~PDF ()
	Virtual destructor, to allow unfettered inheritance.

void	print (std::ostream &os=std::cout, int verbosity=1) const
	Summary printout.

Ranges of validity
virtual double	xMin ()
	Minimum valid x value for this PDF.

virtual double	xMax ()
	Maximum valid x value for this PDF.

virtual double	qMin ()

virtual double	qMax ()
	Maximum valid Q value for this PDF (in GeV). More...

virtual double	q2Min ()
	Minimum valid Q2 value for this PDF (in GeV2).

virtual double	q2Max ()
	Maximum valid Q2 value for this PDF (in GeV2).

int	forcePositive () const
	Check whether the PDF is set to only return positive (definite) values or not. More...

void	setForcePositive (int mode)
	Set whether the PDF will only return positive (definite) values or not.

bool	inPhysicalRangeX (double x) const
	Check whether the given x is physically valid. More...

bool	inPhysicalRangeQ2 (double q2) const
	Check whether the given Q2 is physically valid. More...

bool	inPhysicalRangeQ (double q) const
	Check whether the given Q is physically valid. More...

bool	inPhysicalRangeXQ2 (double x, double q2) const
	Check whether the given (x,Q2) is physically valid.

bool	inPhysicalRangeXQ (double x, double q) const
	Check whether the given (x,Q) is physically valid.

virtual bool	inRangeQ (double q) const
	Grid range check for Q. More...

virtual bool	inRangeQ2 (double q2) const =0
	Grid range check for Q2. More...

virtual bool	inRangeX (double x) const =0
	Grid range check for x. More...

virtual bool	inRangeXQ (double x, double q) const
	Combined range check for x and Q.

bool	inRangeXQ2 (double x, double q2) const
	Combined range check for x and Q2.

Generic member-level metadata (including cascaded metadata from set & config level)
PDFInfo &	info ()
	Get the info class that actually stores and handles the metadata.

const PDFInfo &	info () const
	Get the info class that actually stores and handles the metadata (const version)

PDFSet &	set () const
	Get the PDF set of which this is a member. More...

Member-level metadata
int	memberID () const
	PDF member local ID number. More...

int	lhapdfID () const
	PDF member global LHAPDF ID number. More...

std::string	description () const
	Description of this PDF member.

int	dataversion () const
	Version of this PDF's data file.

std::string	type () const
	Get the type of PDF member that this object represents (central, error)

Parton content and QCD parameters
virtual const std::vector< int > &	flavors () const
	List of flavours defined by this PDF set. More...

void	setFlavors (std::vector< int > const &flavors)
	Manually set/override the list of flavours defined by this PDF set. More...

bool	hasFlavor (int id) const
	Checks whether id is a valid parton for this PDF.

int	orderQCD () const
	Order of QCD at which this PDF has been constructed. More...

int	qcdOrder () const

double	quarkMass (int id) const
	Get a quark mass in GeV by PDG code (\|PID\| = 1-6 only) More...

double	quarkThreshold (int id) const
	Get a flavor scale threshold in GeV by PDG code (\|PID\| = 1-6 only) Convenience interface to the Mass* and Threshold* info keywords. Returns -1 for an undefined PID. More...

QCD running coupling calculation
void	setAlphaS (AlphaS *alphas)
	Set the AlphaS calculator by pointer. More...

void	setAlphaS (AlphaSPtr alphas)
	Set the AlphaS calculator by smart pointer.

bool	hasAlphaS () const
	Check if an AlphaS calculator is set.

AlphaS &	alphaS ()
	Retrieve the AlphaS object for this PDF.

const AlphaS &	alphaS () const
	Retrieve the AlphaS object for this PDF (const)

double	alphasQ (double q) const
	Value of alpha_s(Q2) used by this PDF. More...

double	alphasQ2 (double q2) const
	Value of alpha_s(Q2) used by this PDF. More...

Protected Types
typedef unique_ptr< AlphaS >	AlphaSPtr
	Internal convenience typedef for the AlphaS object handle.

Protected Member Functions
	PDF ()
	Force initialization of the only non-class member.

void	_loadAlphaS ()

std::string	_setname () const
	Get the set name from the member data file path (for internal use only)

Helper methods for info loading / path setting, used by derived types
void	_loadInfo (const std::string &mempath)

void	_loadInfo (const std::string &setname, int member)

void	_loadInfo (int lhaid)

Protected Attributes
std::string	_mempath
	Member data file path.

PDFInfo	_info
	Metadata container.

vector< int >	_flavors
	Locally cached list of supported PIDs (mutable for laziness/caching)

AlphaSPtr	_alphas
	Optionally loaded AlphaS object (mutable for laziness/caching)

int	_forcePos
	Cached flag for whether to return only positive (or positive definite) PDF values. More...

PDF values
virtual double	_xfxQ2 (int id, double x, double q2) const =0
	Calculate the PDF xf(x) value at (x,q2) for the given PID. More...

virtual void	_xfxQ2 (double x, double q2, std::vector< double > &ret) const =0

double	xfxQ2 (int id, double x, double q2) const
	Get the PDF xf(x) value at (x,q2) for the given PID. More...

double	xfxQ (int id, double x, double q) const
	Get the PDF xf(x) value at (x,q) for the given PID. More...

void	xfxQ2 (double x, double q2, std::map< int, double > &rtn) const
	Get the PDF xf(x) value at (x,q2) for all supported PIDs. More...

void	xfxQ (double x, double q, std::map< int, double > &rtn) const
	Get the PDF xf(x) value at (x,q) for all supported PIDs. More...

void	xfxQ2 (double x, double q2, std::vector< double > &rtn) const
	Get the PDF xf(x) value at (x,q2) for "standard" PIDs. More...

void	xfxQ (double x, double q, std::vector< double > &rtn) const
	Get the PDF xf(x) value at (x,q) for "standard" PIDs. More...

std::map< int, double >	xfxQ2 (double x, double q2) const
	Get the PDF xf(x) value at (x,q2) for all supported PIDs. More...

std::map< int, double >	xfxQ (double x, double q) const
	Get the PDF xf(x) value at (x,q) for all supported PIDs. More...

Detailed Description

PDF is the general interface for access to parton density information.

The PDF interface declares the general form of all PDF types, such as Grid based or analytic.

Examples: /examples/analyticpdf.cc, /examples/compatibility.cc, and /tests/testgrid.cc.

Member Function Documentation

◆ _xfxQ2()

virtual double LHAPDF::PDF::_xfxQ2	(	int	id,
		double	x,
		double	q2
	)		const

protectedpure virtual

Calculate the PDF xf(x) value at (x,q2) for the given PID.

This is the key function to be overridden in concrete PDF types, since it actually does the calculation of xf(x,Q2) by analytic, interpolation, or other means. The user-called xfxQ2 method exists so that the physical range and PID checks need only be done in one place, rather than need to be re-implemented in each concrete implementation.

Parameters

id	Parton ID in the PDG scheme
x	Momentum fraction
q2	Squared energy (renormalization) scale

Returns: the value of xf(x,q2)

Implemented in LHAPDF::GridPDF.

◆ alphasQ()

double LHAPDF::PDF::alphasQ ( double q ) const

inline

Value of alpha_s(Q2) used by this PDF.

Calculated numerically, analytically, or interpolated according to metadata, using the AlphaS classes.

◆ alphasQ2()

double LHAPDF::PDF::alphasQ2 ( double q2 ) const

inline

Value of alpha_s(Q2) used by this PDF.

Calculated numerically, analytically, or interpolated according to metadata, using the AlphaS classes.

◆ flavors()

virtual const std::vector<int>& LHAPDF::PDF::flavors ( ) const

inlinevirtual

List of flavours defined by this PDF set.

This list is stored locally after its initial read from the Info object to avoid unnecessary lookups and string decoding, since e.g. it is looked at by every call to the GridPDF's Interpolator and Extrapolator classes.

Todo:: Make virtual for AnalyticPDF? Or allow manual setting of the Info?

Examples: /tests/testgrid.cc.

◆ forcePositive()

int LHAPDF::PDF::forcePositive ( ) const

inline

Check whether the PDF is set to only return positive (definite) values or not.

This is to avoid overshooting in to negative values when interpolating/extrapolating PDFs that sharply decrease towards zero. 0 = unforced, 1 = forced positive, 2 = forced positive definite (>= 1e-10)

◆ inPhysicalRangeQ()

bool LHAPDF::PDF::inPhysicalRangeQ ( double q ) const

inline

Check whether the given Q is physically valid.

Returns false for Q less than 0 (Q must be positive).

◆ inPhysicalRangeQ2()

bool LHAPDF::PDF::inPhysicalRangeQ2 ( double q2 ) const

inline

Check whether the given Q2 is physically valid.

Returns false for Q2 less than 0 (Q must be real-valued).

◆ inPhysicalRangeX()

bool LHAPDF::PDF::inPhysicalRangeX ( double x ) const

inline

Check whether the given x is physically valid.

Returns false for x less than 0 or greater than 1, since it is a momentum fraction and not valid outside those values.

◆ inRangeQ()

virtual bool LHAPDF::PDF::inRangeQ ( double q ) const

inlinevirtual

Grid range check for Q.

Return true when given Q is in the coverage range of this PDF. It actually squares the given Q and returns value from inRangeQ2.

Parameters

q	Energy scale

Returns: Whether q is in range

◆ inRangeQ2()

virtual bool LHAPDF::PDF::inRangeQ2 ( double q2 ) const

pure virtual

Grid range check for Q2.

Return true when given Q2 is in the coverage range of this PDF.

Parameters

q2	Squared energy scale

Returns: Whether q2 is in range

Implemented in LHAPDF::GridPDF.

◆ inRangeX()

virtual bool LHAPDF::PDF::inRangeX ( double x ) const

pure virtual

Grid range check for x.

Return true when given x is in the coverage range of this PDF.

Parameters

x	Momentum fraction

Returns: Whether x is in range

Implemented in LHAPDF::GridPDF.

◆ lhapdfID()

int LHAPDF::PDF::lhapdfID ( ) const

PDF member global LHAPDF ID number.

Obtained from the member ID and the set's LHAPDF ID index

◆ memberID()

int LHAPDF::PDF::memberID ( ) const

inline

PDF member local ID number.

Obtained from the member file path, not Info-based metadata.

◆ orderQCD()

int LHAPDF::PDF::orderQCD ( ) const

inline

Order of QCD at which this PDF has been constructed.

"Order" is defined here and throughout LHAPDF as the maximum number of loops included in the matrix elements, in order to have an integer value for easy use in comparisons, as opposed to "LO", "NLO", etc. strings.

Todo:: Provide a setter function?

◆ qcdOrder()

int LHAPDF::PDF::qcdOrder ( ) const

inline

Deprecated:: Use orderQCD instead

◆ qMax()

virtual double LHAPDF::PDF::qMax ( )

inlinevirtual

Maximum valid Q value for this PDF (in GeV).

Note: This function calls sqrt(q2Max()). For better CPU efficiency and accuracy use q2Max() directly.

◆ qMin()

virtual double LHAPDF::PDF::qMin ( )

inlinevirtual

Minimum valid Q value for this PDF (in GeV).

Note: This function calls sqrt(q2Min()). For better CPU efficiency and accuracy use q2Min() directly.

◆ quarkMass()

double LHAPDF::PDF::quarkMass ( int id ) const

Get a quark mass in GeV by PDG code (|PID| = 1-6 only)

Convenience interface to the Mass* info keywords. Returns -1 for an undefined PID.

Todo:: Provide a setter function?

◆ quarkThreshold()

double LHAPDF::PDF::quarkThreshold ( int id ) const

Get a flavor scale threshold in GeV by PDG code (|PID| = 1-6 only) Convenience interface to the Mass* and Threshold* info keywords. Returns -1 for an undefined PID.

Todo:: Provide a setter function?

◆ set()

PDFSet& LHAPDF::PDF::set ( ) const

inline

Get the PDF set of which this is a member.

Obtained from the member file path, not Info-based metadata.

◆ setAlphaS()

void LHAPDF::PDF::setAlphaS ( AlphaS * alphas )

inline

Set the AlphaS calculator by pointer.

The provided AlphaS must have been new'd, as it will not be copied and ownership passes to this GridPDF: it will be deleted when this PDF goes out of scope or another setAlphaS call is made.

◆ setFlavors()

void LHAPDF::PDF::setFlavors ( std::vector< int > const & flavors )

inline

Manually set/override the list of flavours defined by this PDF set.

Note: The provided vector will be internally sorted into ascending numeric order.

◆ xfxQ() [1/4]

std::map<int, double> LHAPDF::PDF::xfxQ	(	double	x,
		double	q
	)		const

inline

Get the PDF xf(x) value at (x,q) for all supported PIDs.

This version creates a new map on every call: prefer to use the fill-in-place version with a user-supplied map for many calls.

xfxQ will square the given q and return the value from xfxQ2. All grids are defined in q2 rather than q since the natural value in MC programs is squared, so we typically avoid an expensive sqrt() call.

Parameters

x	Momentum fraction
q	Energy (renormalization) scale

Returns: A map of PDF xf(x,q) values

◆ xfxQ() [2/4]

void LHAPDF::PDF::xfxQ	(	double	x,
		double	q,
		std::map< int, double > &	rtn
	)		const

inline

Get the PDF xf(x) value at (x,q) for all supported PIDs.

This version fills a user-supplied map to avoid container construction costs on every call.

Parameters

x	Momentum fraction
q	Energy (renormalization) scale
rtn	Map of PDF xf(x,q) values, to be filled

◆ xfxQ() [3/4]

void LHAPDF::PDF::xfxQ	(	double	x,
		double	q,
		std::vector< double > &	rtn
	)		const

inline

Get the PDF xf(x) value at (x,q) for "standard" PIDs.

This version fills a user-supplied vector to avoid container construction costs on every call.

The filled vector follows the LHAPDF5 convention, with 13 entries running in the PDF ID order [-6, -5, ..., -1, 21, 1, ... 5, 6], i.e. quark PDF values will be at vector index pid+6 and the gluon at index 6.

Parameters

x	Momentum fraction
q	Energy (renormalization) scale
rtn	Vector of PDF xf(x,q) values, to be filled

◆ xfxQ() [4/4]

double LHAPDF::PDF::xfxQ	(	int	id,
		double	x,
		double	q
	)		const

inline

Get the PDF xf(x) value at (x,q) for the given PID.

Parameters

id	PDG parton ID
x	Momentum fraction
q	Energy (renormalization) scale

Returns: The value of xf(x,q2)

Examples: /examples/compatibility.cc, and /tests/testgrid.cc.

◆ xfxQ2() [1/4]

std::map<int, double> LHAPDF::PDF::xfxQ2	(	double	x,
		double	q2
	)		const

Get the PDF xf(x) value at (x,q2) for all supported PIDs.

This version creates a new map on every call: prefer to use the fill-in-place version with a user-supplied map for many calls.

Parameters

x	Momentum fraction
q2	Squared energy (renormalization) scale

Returns: A map of PDF xf(x,q2) values

◆ xfxQ2() [2/4]

void LHAPDF::PDF::xfxQ2	(	double	x,
		double	q2,
		std::map< int, double > &	rtn
	)		const

Get the PDF xf(x) value at (x,q2) for all supported PIDs.

This version fills a user-supplied map to avoid container construction costs on every call.

Parameters

x	Momentum fraction
q2	Squared energy (renormalization) scale
rtn	Map of PDF xf(x,q2) values, to be filled

◆ xfxQ2() [3/4]

void LHAPDF::PDF::xfxQ2	(	double	x,
		double	q2,
		std::vector< double > &	rtn
	)		const

Get the PDF xf(x) value at (x,q2) for "standard" PIDs.

This version fills a user-supplied vector to avoid container construction costs on every call.

Parameters

x	Momentum fraction
q2	Squared energy (renormalization) scale
rtn	Vector of PDF xf(x,q2) values, to be filled

◆ xfxQ2() [4/4]

double LHAPDF::PDF::xfxQ2	(	int	id,
		double	x,
		double	q2
	)		const

Get the PDF xf(x) value at (x,q2) for the given PID.

All grids are defined in Q2 rather than Q since the natural value in MC programs is squared, so we typically avoid an expensive sqrt() call.

Parameters

id	PDG parton ID
x	Momentum fraction
q2	Squared energy (renormalization) scale

Returns: The value of xf(x,q2)

Examples: /examples/analyticpdf.cc, and /tests/testgrid.cc.

Member Data Documentation

◆ _forcePos

int LHAPDF::PDF::_forcePos

mutableprotected

Cached flag for whether to return only positive (or positive definite) PDF values.

A negative value indicates that the flag has not been set. 0 = no forcing, 1 = force positive (i.e. 0 is permitted, negative values are not), 2 = force positive definite (i.e. no values less than 1e-10).

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

/builds/hepcedar/lhapdf/include/LHAPDF/PDF.h

Public Member Functions

Protected Types

Protected Member Functions

Protected Attributes

PDF values

Detailed Description

Member Function Documentation

◆ _xfxQ2()

◆ alphasQ()

◆ alphasQ2()

◆ flavors()

◆ forcePositive()

◆ inPhysicalRangeQ()

◆ inPhysicalRangeQ2()

◆ inPhysicalRangeX()

◆ inRangeQ()

◆ inRangeQ2()

◆ inRangeX()

◆ lhapdfID()

◆ memberID()

◆ orderQCD()

◆ qcdOrder()

◆ qMax()

◆ qMin()

◆ quarkMass()

◆ quarkThreshold()

◆ set()

◆ setAlphaS()

◆ setFlavors()

◆ xfxQ() [1/4]

◆ xfxQ() [2/4]

◆ xfxQ() [3/4]

◆ xfxQ() [4/4]

◆ xfxQ2() [1/4]

◆ xfxQ2() [2/4]

◆ xfxQ2() [3/4]

◆ xfxQ2() [4/4]

Member Data Documentation

◆ _forcePos