sampling.h

#ifndef _SAMPLING
#define _SAMPLING

#include "zipf.h"



using namespace std;


/*
Generic interface for sampling from a relation maintained as tuples.
*/

class Sampling {
public:
	vector<unsigned int> *sample;

	Sampling();
	virtual ~Sampling();

	virtual void Build_Sample(Zipf *relation) = 0;

	//dot product or size of join of two samples, and estimation
	virtual double Dot_Product(Sampling *s);
	virtual double Dot_Product_Estimation(Sampling *s) = 0;

	virtual double Scale_Dot_Product_Estimate(Sampling *s, double est) = 0;
};




/*
Bernoulli sampling with probability p.
an element is sampled if its probability (randomly generated) is smaller than p;
So, if p = 1.0, everyone is sampled, while for p = 0.0 nobody gets into the sample.
*/

class Bernoulli_Sampling : public Sampling {
public:
	double p;

	Bernoulli_Sampling(double p);
	virtual ~Bernoulli_Sampling();

	virtual void Build_Sample(Zipf *relation);

	virtual double Dot_Product_Estimation(Sampling *s);

	virtual double Scale_Dot_Product_Estimate(Sampling *s, double est);
};


#endif