Multiplicative linear congruential generator. More...

#include <Random.h>

Inheritance diagram for casa::MLCG:

Public Member Functions
	MLCG (Int seed1=0, Int seed2=1)
	The constructor allows you to specify seeds.
virtual	~MLCG ()
	The destructor is trivial.
virtual uInt	asuInt ()
	Return the 32-random bits as an unsigned integer.
virtual void	reset ()
	Resets the random number generator.
Int	seed1 () const
	Functions that allow the user to retrieve or change the seed integers.
void	seed1 (Int s)
Int	seed2 () const
void	seed2 (Int s)
void	reseed (Int s1, Int s2)
Private Attributes
Int	itsInitSeedOne

Int	itsInitSeedTwo
Int	itsSeedOne
Int	itsSeedTwo

Detailed Description

Multiplicative linear congruential generator.

Intended use:

Public interface

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25

Prerequisite

A knowledge of C++, in particular inheritance
College level mathematics

Etymology

MLCG stands for "Multiplicative Linear Congruential Generator"

Synopsis

The MLCG class implements a Multiplicative Linear Congruential Generator. In particular, it is an implementation of the double MLCG described in Efficient and Portable Combined Random Number Generators by Pierre L'Ecuyer, appearing in Communications of the ACM, Vol. 31. No. 6. This generator has a fairly long period, and has been statistically analyzed to show that it gives good inter-sample independence.

The constructor has two parameters, both of which are seeds for the generator. As in the ACG generator, both seeds are modified to give a "better" distribution of seed digits. Thus, you can safely use values such as 0 or 1 for the seeds. The MLCG generator used much less state than the ACG generator; only two integers (8 bytes) are needed for each generator.

Warning: This class assumes that the integer and unsigned integer type is exactly 32 bits long;

Example

Thrown Exceptions

AipsError: If a programming error or unexpected numeric size is detected. Should not occur in normal usage.

To Do

Nothing I hope!

Definition at line 305 of file Random.h.

Constructor & Destructor Documentation

casa::MLCG::MLCG	(	Int	seed1 = `0`,
		Int	seed2 = `1`
	)		`[explicit]`

The constructor allows you to specify seeds.

virtual casa::MLCG::~MLCG ( ) [virtual]

The destructor is trivial.

Member Function Documentation

virtual uInt casa::MLCG::asuInt ( ) [virtual]

Return the 32-random bits as an unsigned integer.

Implements casa::RNG.

void casa::MLCG::reseed	(	Int	s1,
		Int	s2
	)		`[inline]`

Definition at line 362 of file Random.h.

References itsInitSeedOne, itsInitSeedTwo, and reset().

virtual void casa::MLCG::reset ( ) [virtual]

Resets the random number generator.

After calling this function the random numbers generated will be the same as if the object had just been constructed.

Implements casa::RNG.

Referenced by reseed(), seed1(), and seed2().

Int casa::MLCG::seed1 ( ) const [inline]

Functions that allow the user to retrieve or change the seed integers.

The seeds returned are not the user supplied values but the values obtained after some deterministic modification to produce a more uniform bit distribution.

Definition at line 340 of file Random.h.

References itsSeedOne.

void casa::MLCG::seed1 ( Int s ) [inline]

Definition at line 345 of file Random.h.

References itsInitSeedOne, and reset().

Int casa::MLCG::seed2 ( ) const [inline]

Definition at line 351 of file Random.h.

References itsSeedTwo.

void casa::MLCG::seed2 ( Int s ) [inline]

Definition at line 356 of file Random.h.

References itsInitSeedTwo, and reset().