gists/c-programming/experiments/static-vs-dynamic-mem-alloc.c

/*
 * static-vs-dynamic-mem-alloc.c
 *
 * Author: Intel A80486DX2-66
 * License: Creative Commons Zero 1.0 Universal
 */

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

#define MULTIPLIER 268435456ULL

void empty(uint8_t** mem);
void static_memory_allocation(uint8_t** mem);
void dynamic_memory_allocation(uint8_t** mem);
long double measure(void (*function)(uint8_t**), long double* c);

void empty(uint8_t** mem) {
	return;
}

void static_memory_allocation(uint8_t** mem) {
	*mem = malloc(MULTIPLIER * sizeof(uint8_t));
	if (*mem == NULL) {
		perror("malloc");
		exit(EXIT_FAILURE);
	}
}

void dynamic_memory_allocation(uint8_t** mem) {
	*mem = malloc(1 * sizeof(uint8_t));
	if (*mem == NULL) {
		perror("malloc");
		exit(EXIT_FAILURE);
	}
	for (size_t i = 1; i < MULTIPLIER; i++) {
		uint8_t* new_memory = realloc(*mem, i * sizeof(uint8_t));
		if (new_memory == NULL) {
			perror("realloc");
			exit(EXIT_FAILURE);
		}
		*mem = new_memory;
	}
}

long double measure(void (*function)(uint8_t**), long double* c) {
	clock_t start;

	start = clock();

	uint8_t* ptr = NULL;
	function(&ptr);
	if (ptr != NULL)
		free(ptr);

	clock_t end = clock();
	long double cpu_time_used = ((long double) (end - start) * 1000000000.l) /
	                            CLOCKS_PER_SEC;

	if (c != NULL) {
		cpu_time_used -= *c;
		printf(": ~%.0Lf nanoseconds\n", cpu_time_used);
	}
	return cpu_time_used;
}

int main(void) {
	long double c = measure(empty, NULL); // empty function call

	printf(" Static memory allocation");
	long double value1 = measure(static_memory_allocation, &c);
	printf("Dynamic memory allocation");
	long double value2 = measure(dynamic_memory_allocation, &c);
	printf("\nStatic memory allocation is ~%.0Lf nanoseconds faster",
	       value2 - value1);

	return EXIT_SUCCESS;
}