#pragma once

#include <cstdint> //uint64_t
#include <cmath> // std::abs

#include "utils/vector.h"
#include "utils/matrix.h"

#include "numerics/mean.h"

namespace numerics::detail{
	
		
	template <typename T>
	inline T standard_deviation_serial(const utils::Vector<T>& v) {
		const uint64_t n = v.size();

		if (n == 0){
			throw std::runtime_error("std_serial: empty vector");
		}

		const T mean_value = numerics::mean(v);

		T sum_squared_diff = T{0};


		for (uint64_t i = 0; i < n; ++i){
			const T diff = v[i] - mean_value;
			sum_squared_diff += diff * diff;
		}

		const T variance = sum_squared_diff / static_cast<T>(n);

		return numerics::sqrt(variance); 
	}


	template <typename T>
	inline T standard_deviation_serial(const utils::Matrix<T>& A) {
	    const uint64_t rows = A.rows();
	    const uint64_t cols = A.cols();

	    const T mean_value = numerics::mean(A);

	    T sum_squared_diff =  T{0};


		for (uint64_t i = 0; i < rows; ++i){
			for (uint64_t j = 0; j < cols; ++j){
				const T diff = A(i,j) - mean_value;
				sum_squared_diff += diff * diff;
			}
		}
		const T variance = sum_squared_diff / static_cast<T>(rows*cols);

		return numerics::sqrt(variance);
	}


} // namespace numerics