C Return Benchmark

bench.c

// INSTRUCTIONS:
// Compile with `gcc -s -O3 -flto -o bench bench.c`
// Run with `./bench 100000 10000`

// IMPORTANT:
// The two parameters are REQUIRED and are the numbers for:
//   1. How many points in the array.
//   2. How many times to cycle through the array.
//
// The numbers are not multiplied to ensure the compiler can't cheat.

#include <time.h>
#include <stdio.h>
#include <stdlib.h>

#define BY_COPY

typedef struct Point Point;

struct Point
{
	float x, y, z;
};

#ifdef BY_COPY

Point Point_init(float x, float y, float z)
{
	return (Point) { x, y, z };
}

Point add(Point* a, Point* b)
{ 
	return (Point) {
		a->x + b->x,
		a->y + b->y,
		a->z + b->z
	};
}

Point sub(Point* a, Point* b)
{
	return (Point) {
		a->x - b->x,
		a->y - b->y,
		a->z - b->z
	};
}

Point foo(Point* p, float n)
{
	Point x = Point_init(n, n, n);
	return add(p, &x);
}

Point bar(Point* p, float n)
{
	Point x = foo(p, n);
	return sub(p, &x);
}

#else

void Point_init(float x, float y, float z, Point* result)
{
	*result = (Point) { x, y, z };
}

void add(Point* a, Point* b, Point* result)
{
	*result = (Point) {
		a->x + b->x,
		a->y + b->y,
		a->z + b->z
	};
}

void sub(Point* a, Point* b, Point* result)
{
	*result = (Point) {
		a->x - b->x,
		a->y - b->y,
		a->z - b->z
	};
}

void foo(Point* p, float n, Point* result)
{
	Point x;
	Point_init(n, n, n, &x);
	add(p, &x, result);
}

void bar(Point* p, float n, Point* result)
{
	Point x;
	foo(p, n, &x);
	sub(p, &x, result);
}

#endif

float calc(Point* p)
{
	return p->x + p->y + p->z;
}

int main(int argc , char** argv)
{
	int pointCount = atoi(argv[1]);

	Point* points = malloc(sizeof(Point) * pointCount);
	for (int i = 0; i < pointCount; ++i) {
		#ifdef BY_COPY
		points[i] = Point_init(i, i, i);
		#else
		Point_init(i, i, i, &points[i]);
		#endif
	}

	clock_t start = clock();

	int cycleCount = atoi(argv[2]);
	for (int c = 0; c < cycleCount; ++c) {
		#ifdef BY_COPY
		if (c % 2 == 0) {
			for (int i = 0; i < pointCount; ++i) {
				Point t = bar(&points[i], i + 1);
				points[i] = add(&points[i], &t);
			}
		}
		else {
			for (int i = 0; i < pointCount; ++i) {
				Point t = bar(&points[i], i + 1);
				points[i] = sub(&points[i], &t);
			}
		}
		#else
		if (c % 2 == 0) {
			for (int i = 0; i < pointCount; ++i) {
				Point t;
				bar(&points[i], i + 1, &t);
				add(&points[i], &t, &points[i]);
			}
		}
		else {
			for (int i = 0; i < pointCount; ++i) {
				Point t;
				bar(&points[i], i + 1, &t);
				sub(&points[i], &t, &points[i]);
			}
		}
		#endif
	}

	double duration = (clock() - start) / (double)CLOCKS_PER_SEC;
	printf("Time: %f\n", duration);

	float total = 0;
	for (int i = 0; i < pointCount; ++i) {
		total += calc(points + i);
	}

	printf("Total: %f\n", total);

	free(points);
	return EXIT_SUCCESS;
}