//
//  analyse.hpp
//  AwesomeAttract0r
//
//  Created by Joshua Moerman on 3/25/12.
//  Copyright (c) 2012 Vadovas. All rights reserved.
//

#ifndef AwesomeAttract0r_analyse_hpp
#define AwesomeAttract0r_analyse_hpp

#include <cmath>

inline double distance_squared(double * p1, double * p2, size_t dimension){
	double s = 0;
	for(unsigned int i = 0; i < dimension; ++i){
		s += (p1[i] - p2[i]) * (p1[i] - p2[i]);
	}
	return s;
}

struct fractal_dimension_settings{
	double doubling;
	double size;
	size_t chunk_size;
	
	fractal_dimension_settings()
	: doubling(2.4)
	, size(0.035)
	, chunk_size(200)
	{}
};

template <typename Iterator>
double fractal_dimension(Iterator begin, Iterator end, size_t const dimension, const fractal_dimension_settings settings = fractal_dimension_settings() ) {
	const double size = settings.size;
	const double totalSize = std::sqrt(dimension);
	
	const double r1 = size * totalSize * size * totalSize;
	const double r2 = r1 * settings.doubling * settings.doubling;
	
	unsigned int counts[2] = {};
	
	while(begin != end){
		auto x0 = *begin++;
		
		for(unsigned int i = 0; i < settings.chunk_size && begin != end; ++i){
			auto x = *begin++;
			auto d = distance_squared(x, x0, dimension);
			if( d <= r1 )
				++counts[0];
			if( d <= r2 )
				++counts[1];
		}
	}
	
	return std::log((double) counts[1] / (double) counts[0]) / std::log(settings.doubling);
}

#endif