/*
 * Copyright (c) Camden Dixie O'Brien
 * SPDX-License-Identifier: AGPL-3.0-only
 */

#include "benchmarking.h"

#include <assert.h>
#include <math.h>
#include <stdio.h>

#define SWAP(x, y) \
	do { \
		const double tmp = x; \
		x = y; \
		y = tmp; \
	} while (0)

clock_t benchmark_start, benchmark_end;

static void sort(double *xs, int n)
{
	if (n <= 0)
		return;

	const double pivot = xs[(n - 1) / 2];
	int lt = 0;
	int eq = 0;
	int gt = n - 1;
	while (eq <= gt) {
		if (xs[eq] < pivot) {
			SWAP(xs[eq], xs[lt]);
			++lt;
			++eq;
		} else if (xs[eq] > pivot) {
			SWAP(xs[eq], xs[gt]);
			--gt;
		} else {
			++eq;
		}
	}

	sort(xs, lt);
	sort(xs + gt + 1, n - (gt + 1));
}

void benchmark_summarise(double *res, int reps, benchmark_summary_t *out)
{
	assert(reps > 0);

	sort(res, reps);
	const double median = res[reps / 2];

	double sum = 0;
	for (int i = 0; i < reps; ++i)
		sum += res[i];
	const double mean = sum / reps;

	double diff_sum = 0;
	for (int i = 0; i < reps; ++i)
		diff_sum += pow(res[i] - mean, 2);
	const double variance = diff_sum / (reps - 1);

	out->reps = reps;
	out->total = sum;
	out->median = median;
	out->mean = mean;
	out->min = res[0];
	out->max = res[reps - 1];
	out->stddev = sqrt(variance);
}

void benchmark_print_header(void)
{
	printf(
	    "%-12s %13s %13s %13s %13s %12s\n", "benchmark", "median (µs)",
	    "mean (µs)", "min (µs)", "max (µs)", "stddev");
}

void benchmark_print(const char *name, const benchmark_summary_t *s)
{
	printf(
	    "%-12s %12.2f %12.2f %12.2f %12.2f %12.2f\n", name, s->median,
	    s->mean, s->min, s->max, s->stddev);
}