PoissonColumnGenerator< T > Class Template Reference

Column generator which generates values with a Poisson distribution. More...

#include <ExecStreamGenerator.h>

Inheritance diagram for PoissonColumnGenerator< T >:

List of all members.

Public Member Functions
	PoissonColumnGenerator (T startValue, double meanDistance, int batchSize, uint seed)
virtual	~PoissonColumnGenerator ()
T	next ()
Private Member Functions
void	generateBatch ()
	Populates the next batch of values.
Private Attributes
T	currentValue
vector< T >	nextValues
	batch of pre-generated values
int	ordinalInBatch
	position in the batch of the last value we returned
T	batchUpper
	upper bound of current batch, will be the lower bound of the next
std::subtractive_rng	rng
double	meanDistance

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Detailed Description

template<class T = int64_t>
class PoissonColumnGenerator< T >

Column generator which generates values with a Poisson distribution.

The Poisson distribution is a statistical distribution which characterizes the intervals between successive events. For example, consider a large sample of a radioactive isotope with a long half-life, and a Geiger counter measuring decay events. The number of events N between time t=0 and t=1 will be Poisson distributed.

This generator generates an ascending sequence of values with a given mean distance between values. For example, the sequence [3, 17, 24, 39, 45] might be the first five values generated if startValue = 0 and meanDistance = 10.

The generator generates a better statistical distribution if you give it a larger value of batchSize.

Author:

Julian Hyde

Definition at line 189 of file ExecStreamGenerator.h.

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Constructor & Destructor Documentation

template<class T = int64_t>

PoissonColumnGenerator< T >::PoissonColumnGenerator	(	T	startValue,
		double	meanDistance,
		int	batchSize,
		uint	seed
	)			[inline, explicit]

Definition at line 202 of file ExecStreamGenerator.h.

References PoissonColumnGenerator< T >::batchUpper, PoissonColumnGenerator< T >::nextValues, and PoissonColumnGenerator< T >::ordinalInBatch.

                   : rng(seed)
    {
        assert(batchSize > 0);
        assert(meanDistance > 0);
        assert(meanDistance * batchSize >= 1);
        this->batchUpper = startValue;
        nextValues.resize(batchSize);
        this->ordinalInBatch = batchSize;
        this->meanDistance = meanDistance;
    }

template<class T = int64_t>

virtual PoissonColumnGenerator< T >::~PoissonColumnGenerator

(

)

[inline, virtual]

Definition at line 217 of file ExecStreamGenerator.h.

        {}

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Member Function Documentation

template<class T = int64_t>

T PoissonColumnGenerator< T >::next

(

)

[inline, virtual]

Implements ColumnGenerator< T >.

Definition at line 220 of file ExecStreamGenerator.h.

References PoissonColumnGenerator< T >::generateBatch(), PoissonColumnGenerator< T >::nextValues, and PoissonColumnGenerator< T >::ordinalInBatch.

    {
        if (ordinalInBatch >= nextValues.size()) {
            generateBatch();
        }
        return nextValues[ordinalInBatch++];
    }

template<class T = int64_t>

void PoissonColumnGenerator< T >::generateBatch

(

)

[inline, private]

Populates the next batch of values.

Definition at line 230 of file ExecStreamGenerator.h.

References PoissonColumnGenerator< T >::batchUpper, PoissonColumnGenerator< T >::meanDistance, PoissonColumnGenerator< T >::nextValues, PoissonColumnGenerator< T >::ordinalInBatch, and PoissonColumnGenerator< T >::rng.

Referenced by PoissonColumnGenerator< T >::next().

                         {
        // The next batch will contain nextValues.size() values with a mean
        // inter-value distance of meanDistance, hence its values will range
        // from batchLower to batchLower + nextValues.size() * meanDistance.
        T batchLower = this->batchUpper;
        int batchRange = (int) (meanDistance * nextValues.size());
        T batchUpper = batchLower + batchRange;
        assert(batchUpper > batchLower);
        for (int i = 0; i < nextValues.size(); i++) {
            nextValues[i] = batchLower + static_cast<T>(rng(batchRange));
        }
        std::sort(nextValues.begin(), nextValues.end());
        this->batchUpper = batchUpper;
        this->ordinalInBatch = 0;
    }

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Member Data Documentation

template<class T = int64_t>

T PoissonColumnGenerator< T >::currentValue [private]

Definition at line 191 of file ExecStreamGenerator.h.

template<class T = int64_t>

vector<T> PoissonColumnGenerator< T >::nextValues [private]

batch of pre-generated values

Definition at line 193 of file ExecStreamGenerator.h.

Referenced by PoissonColumnGenerator< T >::generateBatch(), PoissonColumnGenerator< T >::next(), and PoissonColumnGenerator< T >::PoissonColumnGenerator().

template<class T = int64_t>

int PoissonColumnGenerator< T >::ordinalInBatch [private]

position in the batch of the last value we returned

Definition at line 195 of file ExecStreamGenerator.h.

Referenced by PoissonColumnGenerator< T >::generateBatch(), PoissonColumnGenerator< T >::next(), and PoissonColumnGenerator< T >::PoissonColumnGenerator().

template<class T = int64_t>

T PoissonColumnGenerator< T >::batchUpper [private]

upper bound of current batch, will be the lower bound of the next

Definition at line 197 of file ExecStreamGenerator.h.

Referenced by PoissonColumnGenerator< T >::generateBatch(), and PoissonColumnGenerator< T >::PoissonColumnGenerator().

template<class T = int64_t>

std::subtractive_rng PoissonColumnGenerator< T >::rng [private]

Definition at line 198 of file ExecStreamGenerator.h.

Referenced by PoissonColumnGenerator< T >::generateBatch().

template<class T = int64_t>

double PoissonColumnGenerator< T >::meanDistance [private]

Definition at line 199 of file ExecStreamGenerator.h.

Referenced by PoissonColumnGenerator< T >::generateBatch().

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

• /home/pub/open/dev/fennel/test/ExecStreamGenerator.h

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