VLAT is the Visibility LookAhead Thread. This thread advances a visibility iterator and fills the data indicated by the visibility iterator into the VlaData buffer ring. More...

#include <VLAT2.h>

Inheritance diagram for casa::vi::VLAT:

List of all members.

Classes
class	FillerDictionary
class	SweepTerminated
Public Member Functions
	VLAT (AsynchronousInterface *)
	~VLAT ()
void	clearFillTerminationRequest ()
void	initialize (const ROVisibilityIterator &rovi)
void	initialize (const Block< MeasurementSet > &mss, const Block< Int > &sortColumns, Bool addDefaultSortCols, Double timeInterval, Bool writable)
Bool	isTerminated () const
void	setModifiers (RoviaModifiers &modifiers)
void	setPrefetchColumns (const PrefetchColumns &prefetchColumns)
void	requestSweepTermination ()
void	terminate ()
Protected Types
typedef vector< VlatFunctor * >	Fillers
Protected Member Functions
void	applyModifiers (ROVisibilityIterator rovi, VisibilityIterator vi)
void	alignWriteIterator (SubChunkPair subchunk)
void	checkFiller (VisBufferComponents::EnumType id)
void	createFillerDictionary ()
void	fillDatum (VlaDatum *datum)
void	fillDatumMiscellanyAfter (VlaDatum *datum)
void	fillDatumMiscellanyBefore (VlaDatum *datum)
void	fillLsrInfo (VlaDatum *datum)
void	flushWrittenData ()
void	handleWrite ()
void *	run ()
Bool	sweepTerminationRequested () const
void	sweepVi ()
void	throwIfSweepTerminated ()
Bool	waitForViReset ()
void	waitUntilFillCanStart ()
Private Attributes
const InterfaceController *	controller_p
	class NullaryPredicate { public:
FillerDictionary	fillerDictionary_p
Fillers	fillers_p
AsynchronousInterface *	interface_p
Block< MeasurementSet >	measurementSets_p
SubChunkPair	readSubchunk_p
RoviaModifiers	roviaModifiers_p
volatile Bool	sweepTerminationRequested_p
Bool	threadTerminated_p
ROVisibilityIterator *	visibilityIterator_p
VlaData *	vlaData_p
VisibilityIterator *	writeIterator_p
SubChunkPair	writeSubchunk_p

Detailed Description

VLAT is the Visibility LookAhead Thread. This thread advances a visibility iterator and fills the data indicated by the visibility iterator into the VlaData buffer ring.

Intended use:

Internal

Review Status

Date Reviewed:: yyyy/mm/dd

Prerequisite

VisBuffer
VisBufferAsync
ROVisibilityIteratorAsync
VlaData
VLAT

Etymology

VLAT is the Visibility LookAhead Thread. It is not related to the more common NRAO acronym VLA.

Synopsis

The VLAT is a thread object that buffers up data from successive visibility iterator positions in a MeasurementSet. It is part of the backend to a ROVisibilityIteratorAsync (ROVIA) object used by the main thread to replace the normal, synchronous ROVisibilityIterator. When the user creates a ROVIA object the information normally used to create a ROVisibilityIterator is passed to the VLAT which uses it to create a ROVisibilityIterator local to itself. The VLAT then uses this ROVisibilityIterator to fill buffers in the VlaData-managed buffer ring (this interaction is described in VlaData). Filling consists of attaching VLAT's ROVisibilityIterator to the VisBufferAsync object associated with a buffer and then calling the fill operations for the data items (e.g., visCube, Ant1, etc.) which the user has requested be prefetched. The fill operations will likely result in synchronous I/O operations being performed by the column access methods related to the Table system (memory-resident tables, columns, etc., may be able to satisfy a fill operation without performing I/O).

The thread may be terminated by calling the terminate method. This will cause the VLAT to terminate when it notices the termination request. The termination may not be immediate since the VLAT may be engaged in a syncrhonous I/O operation and is uanble to detect the termination request until that I/O has completed.

Normally the VLAT sweeps the VI to the end of the measurement set and then awaits further instructions. The main thread may stop the sweep early by calling VlaData::terminateSweep which will eventually be detected by the VLAT and result in a coordinated reset of the sweep. When the sweep reset is applied the VLAT will also detect visibility iterator modification requests (e.g., setRowBlocking, selectChannel, setInterval, etc.) that were queued up in VlaData; for the set of available VI modification requests supported see ROVisibilityIteratorAsync.

Example

Motivation

Thrown Exceptions

AipsError for unrecoverable errors. These will not be caught (in C++ anyway) and cause application termination.

Definition at line 213 of file VLAT2.h.

Member Typedef Documentation

typedef vector<VlatFunctor *> casa::vi::VLAT::Fillers [protected]

Definition at line 248 of file VLAT2.h.

Constructor & Destructor Documentation

casa::vi::VLAT::VLAT ( AsynchronousInterface * )

casa::vi::VLAT::~VLAT ( )

Member Function Documentation

void casa::vi::VLAT::alignWriteIterator ( SubChunkPair subchunk ) [protected]

void casa::vi::VLAT::applyModifiers	(	ROVisibilityIterator *	rovi,
		VisibilityIterator *	vi
	)		`[protected]`

void casa::vi::VLAT::checkFiller ( VisBufferComponents::EnumType id ) [protected]

void casa::vi::VLAT::clearFillTerminationRequest ( )

void casa::vi::VLAT::createFillerDictionary ( ) [protected]

void casa::vi::VLAT::fillDatum ( VlaDatum * datum ) [protected]

void casa::vi::VLAT::fillDatumMiscellanyAfter ( VlaDatum * datum ) [protected]

void casa::vi::VLAT::fillDatumMiscellanyBefore ( VlaDatum * datum ) [protected]

void casa::vi::VLAT::fillLsrInfo ( VlaDatum * datum ) [protected]

void casa::vi::VLAT::flushWrittenData ( ) [protected]

void casa::vi::VLAT::handleWrite ( ) [protected]

void casa::vi::VLAT::initialize ( const ROVisibilityIterator & rovi )

void casa::vi::VLAT::initialize	(	const Block< MeasurementSet > &	mss,
		const Block< Int > &	sortColumns,
		Bool	addDefaultSortCols,
		Double	timeInterval,
		Bool	writable
	)

Bool casa::vi::VLAT::isTerminated ( ) const

void casa::vi::VLAT::requestSweepTermination ( )

void* casa::vi::VLAT::run ( ) [protected, virtual]

Implements casa::async::Thread.

void casa::vi::VLAT::setModifiers ( RoviaModifiers & modifiers )

void casa::vi::VLAT::setPrefetchColumns ( const PrefetchColumns & prefetchColumns )

Bool casa::vi::VLAT::sweepTerminationRequested ( ) const [protected]

void casa::vi::VLAT::sweepVi ( ) [protected]

void casa::vi::VLAT::terminate ( ) [virtual]

Reimplemented from casa::async::Thread.

void casa::vi::VLAT::throwIfSweepTerminated ( ) [protected]

Bool casa::vi::VLAT::waitForViReset ( ) [protected]

void casa::vi::VLAT::waitUntilFillCanStart ( ) [protected]

Member Data Documentation

const InterfaceController* casa::vi::VLAT::controller_p [private]

class NullaryPredicate { public:

virtual ~NullaryPredicate () {}
virtual Bool operator () () const = 0;

};

class FillCanStartOrSweepTermination : public NullaryPredicate {

public:

FillCanStartOrSweepTermination (VlaData * vlaData, AsynchronousInterface * interface)
: interface_p (interface),
  vlaData_p (vlaData)
{}

Bool operator() () const
{
    return vlaData_p->fillCanStart () || interface_p->isSweepTerminationRequested ();
}

private:

AsynchronousInterface * interface_p;
VlaData * vlaData_p;

};

class ViResetOrLookaheadTermination : public NullaryPredicate {

public:

ViResetOrLookaheadTermination (AsynchronousInterface * interface)
: interface_p (interface)
{}

Bool operator() () const
{
    Bool viWasReset_p = interface_p->viResetRequested;

    return viWasReset_p || interface_p->isLookaheadTerminationRequested ();
}

private: