An FTMachine for Gridding Single Dish data. More...

#include <SDGrid.h>

Inheritance diagram for casa::SDGrid:

Public Member Functions
	SDGrid (SkyJones &sj, Int cachesize, Int tilesize, String convType="BOX", Int userSupport=-1)
	Constructor: cachesize is the size of the cache in words (e.g.
	SDGrid (MPosition &ml, SkyJones &sj, Int cachesize, Int tilesize, String convType="BOX", Int userSupport=-1)
	SDGrid (Int cachesize, Int tilesize, String convType="BOX", Int userSupport=-1)
	SDGrid (MPosition &ml, Int cachesize, Int tilesize, String convType="BOX", Int userSupport=-1)
	SDGrid (MPosition &ml, Int cachesize, Int tilesize, String convType="TGAUSS", Float truncate=-1.0, Float gwidth=0.0, Float jwidth=0.0)
	SDGrid (const SDGrid &other)
	Copy constructor.
SDGrid &	operator= (const SDGrid &other)
	Assignment operator.
	~SDGrid ()
void	initializeToVis (ImageInterface< Complex > &image, const VisBuffer &vb)
	Initialize transform to Visibility plane using the image as a template.
void	finalizeToVis ()
	Finalize transform to Visibility plane: flushes the image cache and shows statistics if it is being used.
void	initializeToSky (ImageInterface< Complex > &image, Matrix< Float > &weight, const VisBuffer &vb)
	Initialize transform to Sky plane: initializes the image.
void	finalizeToSky ()
	Finalize transform to Sky plane: flushes the image cache and shows statistics if it is being used.
void	get (VisBuffer &vb, Int row=-1)
	Get actual coherence from grid by degridding.
void	put (const VisBuffer &vb, Int row=-1, Bool dopsf=False, FTMachine::Type type=FTMachine::OBSERVED)
	Put coherence to grid by gridding.
ImageInterface< Complex > &	getImage (Matrix< Float > &, Bool normalize=True)
	Get the final image: do the Fourier transform and grid-correct, then optionally normalize by the summed weights.
virtual void	normalizeImage (Lattice< Complex > &, const Matrix< Double > &, Lattice< Float > &, Bool)
void	getWeightImage (ImageInterface< Float > &, Matrix< Float > &)
	Get the final weights image.
virtual Bool	changed (const VisBuffer &vb)
	Has this operator changed since the last application?
virtual void	setMiscInfo (const Int qualifier)
	set the order of the Taylor term for MFS this is to tell A-Projection to qualify the accumulated avgPB for each Taylor term in the CFCache.
virtual void	ComputeResiduals (VisBuffer &, Bool)
	Make the VB and VBStore interefaces for the interim re-factoring work.
virtual String	name () const
	Return the name of the machine.
Private Member Functions
void	findPBAsConvFunction (const ImageInterface< Complex > &image, const VisBuffer &vb)
	Find the Primary beam and convert it into a convolution buffer.
Array< Complex > *	getDataPointer (const IPosition &, Bool)
	Get the appropriate data pointer.
Array< Float > *	getWDataPointer (const IPosition &, Bool)
void	ok ()
void	init ()
Int	getIndex (const ROMSPointingColumns &mspc, const Double &time, const Double &interval)
Bool	getXYPos (const VisBuffer &vb, Int row)
MDirection	directionMeas (const ROMSPointingColumns &mspc, const Int &index)
	get the MDirection from a chosen column of pointing table
MDirection	directionMeas (const ROMSPointingColumns &mspc, const Int &index, const Double &time)
MDirection	interpolateDirectionMeas (const ROMSPointingColumns &mspc, const Double &time, const Int &index, const Int &index1, const Int &index2)
Private Attributes
SkyJones *	sj_p
LatticeCache< Complex > *	imageCache
	Image cache.
LatticeCache< Float > *	wImageCache
Int	cachesize
	Sizes.
Int	tilesize
Bool	isTiled
	Is this tiled?
ImageInterface< Float > *	wImage
	Storage for weights.
Lattice< Complex > *	arrayLattice
	Array lattice.
Lattice< Float > *	wArrayLattice
Lattice< Complex > *	lattice
	Lattice.
Lattice< Float > *	wLattice
String	convType
IPosition	centerLoc
	Useful IPositions.
IPosition	offsetLoc
Array< Complex >	griddedData
	Array for non-tiled gridding.
Array< Float >	wGriddedData
DirectionCoordinate	directionCoord
MDirection::Convert *	pointingToImage
Vector< Double >	xyPos
Vector< Double >	xyPosMovingOrig_p
	Original xypos of moving source.
MDirection	worldPosMeas
Cube< Int >	flags
Vector< Float >	convFunc
Int	convSampling
Int	convSize
Int	convSupport
Int	userSetSupport_p
Float	truncate_p
Float	gwidth_p
Float	jwidth_p
Int	lastIndex_p

Detailed Description

An FTMachine for Gridding Single Dish data.

Intended use:

Public interface

Prerequisite

FTMachine module
SkyEquation module
VisBuffer module

Etymology

FTMachine is a Machine for Fourier Transforms. SDGrid does Single Dish gridding in a similar way

Synopsis

The SkyEquation needs to be able to perform Fourier transforms on visibility data and to grid single dish data. SDGrid allows efficient Single Dish processing using a VisBuffer which encapsulates a chunk of visibility (typically all baselines for one time) together with all the information needed for processing (e.g. direction coordinates).

Gridding and degridding in SDGrid are performed using a novel sort-less algorithm. In this approach, the gridded plane is divided into small patches, a cache of which is maintained in memory using a general-purpose LatticeCache class. As the (time-sorted) visibility data move around slowly in the image plane, patches are swapped in and out as necessary. Thus, optimally, one would keep at least one patch per scan line of data.

A grid cache is defined on construction. If the gridded image plane is smaller than this, it is kept entirely in memory and all gridding and degridding is done entirely in memory. Otherwise a cache of tiles is kept an paged in and out as necessary. Optimally the cache should be big enough to hold all polarizations and frequencies for one complete scan line. The paging rate will then be small. As the cache size is reduced below this critical value, paging increases. The algorithm will work for only one patch but it will be very slow!

The gridding and degridding steps are implemented in Fortran for speed. In gridding, the visibilities are added onto the grid points in the neighborhood using a weighting function. In degridding, the value is derived by a weight summ of the same points, using the same weighting function.

Example

See the example for SkyModel .

Motivation

Define an interface to allow efficient processing of chunks of visibility data

Definition at line 118 of file SDGrid.h.

Constructor & Destructor Documentation

casa::SDGrid::SDGrid	(	SkyJones &	sj,
		Int	cachesize,
		Int	tilesize,
		String	convType = `"BOX"`,
		Int	userSupport = `-1`
	)

Constructor: cachesize is the size of the cache in words (e.g.

a few million is a good number), tilesize is the size of the tile used in gridding (cannot be less than 12, 16 works in most cases), and convType is the type of gridding used (SF is prolate spheriodal wavefunction, and BOX is plain box-car summation). mLocation is the position to be used in some phase rotations. If mTangent is specified then the uvw rotation is done for that location iso the image center. userSupport is to allow larger support for the convolution if the user wants it ..-1 will use the default i.e 1 for BOX and 3 for others

casa::SDGrid::SDGrid	(	MPosition &	ml,
		SkyJones &	sj,
		Int	cachesize,
		Int	tilesize,
		String	convType = `"BOX"`,
		Int	userSupport = `-1`
	)

casa::SDGrid::SDGrid	(	Int	cachesize,
		Int	tilesize,
		String	convType = `"BOX"`,
		Int	userSupport = `-1`
	)

casa::SDGrid::SDGrid	(	MPosition &	ml,
		Int	cachesize,
		Int	tilesize,
		String	convType = `"BOX"`,
		Int	userSupport = `-1`
	)

casa::SDGrid::SDGrid	(	MPosition &	ml,
		Int	cachesize,
		Int	tilesize,
		String	convType = `"TGAUSS"`,
		Float	truncate = `-1.0`,
		Float	gwidth = `0.0`,
		Float	jwidth = `0.0`
	)

casa::SDGrid::SDGrid ( const SDGrid & other )

Copy constructor.

casa::SDGrid::~SDGrid ( )

Member Function Documentation

virtual Bool casa::SDGrid::changed ( const VisBuffer & vb ) [virtual]

Has this operator changed since the last application?

Reimplemented from casa::FTMachine.

virtual void casa::SDGrid::ComputeResiduals	(	VisBuffer &	vb,
		Bool	useCorrected
	)		`[inline, virtual]`

Make the VB and VBStore interefaces for the interim re-factoring work.

Finally removed the VB interface.

Implements casa::FTMachine.

Definition at line 194 of file SDGrid.h.

MDirection casa::SDGrid::directionMeas	(	const ROMSPointingColumns &	mspc,
		const Int &	index
	)		`[private]`

get the MDirection from a chosen column of pointing table

MDirection casa::SDGrid::directionMeas	(	const ROMSPointingColumns &	mspc,
		const Int &	index,
		const Double &	time
	)		`[private]`

void casa::SDGrid::finalizeToSky ( ) [virtual]

Finalize transform to Sky plane: flushes the image cache and shows statistics if it is being used.

DOES NOT DO THE FINAL TRANSFORM!

Implements casa::FTMachine.

void casa::SDGrid::finalizeToVis ( ) [virtual]

Finalize transform to Visibility plane: flushes the image cache and shows statistics if it is being used.

Implements casa::FTMachine.

void casa::SDGrid::findPBAsConvFunction	(	const ImageInterface< Complex > &	image,
		const VisBuffer &	vb
	)		`[private]`

Find the Primary beam and convert it into a convolution buffer.

void casa::SDGrid::get	(	VisBuffer &	vb,
		Int	row = `-1`
	)		`[virtual]`

Get actual coherence from grid by degridding.

Implements casa::FTMachine.

Array<Complex>* casa::SDGrid::getDataPointer	(	const IPosition &	,
		Bool
	)		`[private]`

Get the appropriate data pointer.

ImageInterface<Complex>& casa::SDGrid::getImage	(	Matrix< Float > &	,
		Bool	normalize = `True`
	)		`[virtual]`

Get the final image: do the Fourier transform and grid-correct, then optionally normalize by the summed weights.

Implements casa::FTMachine.

Int casa::SDGrid::getIndex	(	const ROMSPointingColumns &	mspc,
		const Double &	time,
		const Double &	interval
	)		`[private]`

Array<Float>* casa::SDGrid::getWDataPointer	(	const IPosition &	,
		Bool
	)		`[private]`

void casa::SDGrid::getWeightImage	(	ImageInterface< Float > &	,
		Matrix< Float > &
	)		`[virtual]`

Get the final weights image.

Implements casa::FTMachine.

Bool casa::SDGrid::getXYPos	(	const VisBuffer &	vb,
		Int	row
	)		`[private]`

void casa::SDGrid::init ( ) [private]

void casa::SDGrid::initializeToSky	(	ImageInterface< Complex > &	image,
		Matrix< Float > &	weight,
		const VisBuffer &	vb
	)		`[virtual]`

Initialize transform to Sky plane: initializes the image.

Implements casa::FTMachine.

void casa::SDGrid::initializeToVis	(	ImageInterface< Complex > &	image,
		const VisBuffer &	vb
	)		`[virtual]`

Initialize transform to Visibility plane using the image as a template.

The image is loaded and Fourier transformed.

Implements casa::FTMachine.

MDirection casa::SDGrid::interpolateDirectionMeas	(	const ROMSPointingColumns &	mspc,
		const Double &	time,
		const Int &	index,
		const Int &	index1,
		const Int &	index2
	)		`[private]`