// Copyright ⓒ 2018-2021 ThePhD.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//  See https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr.adoc for documentation.

#include <benchmarks/statistics.hpp>

#include <vector>
#include <algorithm>
#include <numeric>
#include <cmath>

double compute_mean(const std::vector<double>& v) {
	if (v.size() == 0) {
		return 0.0;
	}
	double mean = std::accumulate(std::begin(v), std::end(v), 0.0) / v.size();
	return mean;
}

double compute_variance(const std::vector<double>& v) {
	if (v.size() == 0) {
		return 0.0;
	}
	double mean		= compute_mean(v);
	auto variance_accum = [&mean](double a, double s) {
		double diff = (s - mean);
		return a + (diff * diff);
	};
	double variance = std::accumulate(std::begin(v), std::end(v), 0.0, variance_accum) / v.size();
	return variance;
}

double compute_stddev(const std::vector<double>& v) {
	return std::sqrt(compute_variance(v));
}

double compute_index_of_dispersion(const std::vector<double>& v) {
	double variance = compute_variance(v);
	double mean	= compute_mean(v);
	if (mean == 0.0) {
		return 0.0;
	}
	return variance / mean;
}

double compute_max(const std::vector<double>& v) {
	return *(std::max_element(std::begin(v), std::end(v)));
}

double compute_min(const std::vector<double>& v) {
	return *(std::min_element(std::begin(v), std::end(v)));
}

#include <cstdint>

//  Windows
#ifdef _WIN32

#include <intrin.h>
uint64_t rdtsc() {
	return __rdtsc();
}
//  Linux/GCC
#else
uint64_t rdtsc() {
	unsigned int lo, hi;
	__asm__ __volatile__("rdtsc"
					 : "=a"(lo), "=d"(hi));
	return ((uint64_t)hi << 32) | lo;
}
#endif