casacore::MeasTableMul Class Reference

MeasTableMul provides thread-safe access to time-dependent multiplier matrices. More...

#include <MeasTableMul.h>

Inheritance diagram for casacore::MeasTableMul:

Public Member Functions
	MeasTableMul ()
virtual	~MeasTableMul ()
void	clear ()
CountedPtr< Matrix< Double > >	getArray (Double time, Double epsilon)
virtual void	init ()=0
virtual void	calc (Matrix< Double > &, Double time)=0
Protected Attributes
Mutex	itsMutex
Int64	itsLastUsed
vector< Int64 >	itsUsed
vector< Double >	itsTimes
vector< CountedPtr< Matrix < Double > > >	itsArrays
Matrix< Double >	itsDefArray

Detailed Description

MeasTableMul provides thread-safe access to time-dependent multiplier matrices.

Intended use:

Internal

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25
Test programs:: tMeasMath

Synopsis

MeasTableMul is a helper class for MeasTable to provide thread-safe access to the various multiplier matrices for nutation, aberration, and solar position. These matrices are dependent on the epoch.

It is an abstract base class for specific derived classes dealing with the various effects. This base class provides a cache to keep the matrices for various epochs alive. The idea is that a program will process epochs in order, where multiple threads can handle different epochs.
When the cache is full, the least recently used entry is replaced by the new matrix.

The cache does not hold Matrix objects themselves, but a CountedPtr<Matrix> to avoid that in one thread a Matrix is removed from the cache, while another thread is still using that Matrix. This assumes that CountedPtr is compiled thread-safe.

The class provides two virtual functions.

init is called on the first access and makes it possible for the derived class to precompute some variables. In particular, itsDefMatrix should be filled with default values.
calc is called on each access and should return the matrix valid for the given epoch. Prior to calling this function, the class will copy itsDefMatrix to the result which also defines the shape of the result. Note that this function is only called if the matrix for the given epoch is not in the cache.