git/t/helper/test-mergesort.c

#include "test-tool.h"
#include "cache.h"
#include "mergesort.h"

struct line {
	char *text;
	struct line *next;
};

static void *get_next(const void *a)
{
	return ((const struct line *)a)->next;
}

static void set_next(void *a, void *b)
{
	((struct line *)a)->next = b;
}

static int compare_strings(const void *a, const void *b)
{
	const struct line *x = a, *y = b;
	return strcmp(x->text, y->text);
}

static int sort_stdin(void)
{
	struct line *line, *p = NULL, *lines = NULL;
	struct strbuf sb = STRBUF_INIT;

	while (!strbuf_getline(&sb, stdin)) {
		line = xmalloc(sizeof(struct line));
		line->text = strbuf_detach(&sb, NULL);
		if (p) {
			line->next = p->next;
			p->next = line;
		} else {
			line->next = NULL;
			lines = line;
		}
		p = line;
	}

	lines = llist_mergesort(lines, get_next, set_next, compare_strings);

	while (lines) {
		puts(lines->text);
		lines = lines->next;
	}
	return 0;
}

static void dist_sawtooth(int *arr, int n, int m)
{
	int i;
	for (i = 0; i < n; i++)
		arr[i] = i % m;
}

static void dist_rand(int *arr, int n, int m)
{
	int i;
	for (i = 0; i < n; i++)
		arr[i] = rand() % m;
}

static void dist_stagger(int *arr, int n, int m)
{
	int i;
	for (i = 0; i < n; i++)
		arr[i] = (i * m + i) % n;
}

static void dist_plateau(int *arr, int n, int m)
{
	int i;
	for (i = 0; i < n; i++)
		arr[i] = (i < m) ? i : m;
}

static void dist_shuffle(int *arr, int n, int m)
{
	int i, j, k;
	for (i = j = 0, k = 1; i < n; i++)
		arr[i] = (rand() % m) ? (j += 2) : (k += 2);
}

#define DIST(name) { #name, dist_##name }

static struct dist {
	const char *name;
	void (*fn)(int *arr, int n, int m);
} dist[] = {
	DIST(sawtooth),
	DIST(rand),
	DIST(stagger),
	DIST(plateau),
	DIST(shuffle),
};

static void mode_copy(int *arr, int n)
{
	/* nothing */
}

static void mode_reverse(int *arr, int n)
{
	int i, j;
	for (i = 0, j = n - 1; i < j; i++, j--)
		SWAP(arr[i], arr[j]);
}

static void mode_reverse_1st_half(int *arr, int n)
{
	mode_reverse(arr, n / 2);
}

static void mode_reverse_2nd_half(int *arr, int n)
{
	int half = n / 2;
	mode_reverse(arr + half, n - half);
}

static int compare_ints(const void *av, const void *bv)
{
	const int *ap = av, *bp = bv;
	int a = *ap, b = *bp;
	return (a > b) - (a < b);
}

static void mode_sort(int *arr, int n)
{
	QSORT(arr, n, compare_ints);
}

static void mode_dither(int *arr, int n)
{
	int i;
	for (i = 0; i < n; i++)
		arr[i] += i % 5;
}

#define MODE(name) { #name, mode_##name }

static struct mode {
	const char *name;
	void (*fn)(int *arr, int n);
} mode[] = {
	MODE(copy),
	MODE(reverse),
	MODE(reverse_1st_half),
	MODE(reverse_2nd_half),
	MODE(sort),
	MODE(dither),
};

static struct stats {
	int get_next, set_next, compare;
} stats;

struct number {
	int value, rank;
	struct number *next;
};

static void *get_next_number(const void *a)
{
	stats.get_next++;
	return ((const struct number *)a)->next;
}

static void set_next_number(void *a, void *b)
{
	stats.set_next++;
	((struct number *)a)->next = b;
}

static int compare_numbers(const void *av, const void *bv)
{
	const struct number *an = av, *bn = bv;
	int a = an->value, b = bn->value;
	stats.compare++;
	return (a > b) - (a < b);
}

static void clear_numbers(struct number *list)
{
	while (list) {
		struct number *next = list->next;
		free(list);
		list = next;
	}
}

static int test(const struct dist *dist, const struct mode *mode, int n, int m)
{
	int *arr;
	size_t i;
	struct number *curr, *list, **tail;
	int is_sorted = 1;
	int is_stable = 1;
	const char *verdict;
	int result = -1;

	ALLOC_ARRAY(arr, n);
	dist->fn(arr, n, m);
	mode->fn(arr, n);
	for (i = 0, tail = &list; i < n; i++) {
		curr = xmalloc(sizeof(*curr));
		curr->value = arr[i];
		curr->rank = i;
		*tail = curr;
		tail = &curr->next;
	}
	*tail = NULL;

	stats.get_next = stats.set_next = stats.compare = 0;
	list = llist_mergesort(list, get_next_number, set_next_number,
			       compare_numbers);

	QSORT(arr, n, compare_ints);
	for (i = 0, curr = list; i < n && curr; i++, curr = curr->next) {
		if (arr[i] != curr->value)
			is_sorted = 0;
		if (curr->next && curr->value == curr->next->value &&
		    curr->rank >= curr->next->rank)
			is_stable = 0;
	}
	if (i < n) {
		verdict = "too short";
	} else if (curr) {
		verdict = "too long";
	} else if (!is_sorted) {
		verdict = "not sorted";
	} else if (!is_stable) {
		verdict = "unstable";
	} else {
		verdict = "OK";
		result = 0;
	}

	printf("%-9s %-16s %8d %8d %8d %8d %8d %s\n",
	       dist->name, mode->name, n, m, stats.get_next, stats.set_next,
	       stats.compare, verdict);

	clear_numbers(list);
	free(arr);

	return result;
}

/*
 * A version of the qsort certification program from "Engineering a Sort
 * Function" by Bentley and McIlroy, Software—Practice and Experience,
 * Volume 23, Issue 11, 1249–1265 (November 1993).
 */
static int run_tests(int argc, const char **argv)
{
	const char *argv_default[] = { "100", "1023", "1024", "1025" };
	if (!argc)
		return run_tests(ARRAY_SIZE(argv_default), argv_default);
	printf("%-9s %-16s %8s %8s %8s %8s %8s %s\n",
	       "distribut", "mode", "n", "m", "get_next", "set_next",
	       "compare", "verdict");
	while (argc--) {
		int i, j, m, n = strtol(*argv++, NULL, 10);
		for (i = 0; i < ARRAY_SIZE(dist); i++) {
			for (j = 0; j < ARRAY_SIZE(mode); j++) {
				for (m = 1; m < 2 * n; m *= 2) {
					if (test(&dist[i], &mode[j], n, m))
						return 1;
				}
			}
		}
	}
	return 0;
}

int cmd__mergesort(int argc, const char **argv)
{
	if (argc == 2 && !strcmp(argv[1], "sort"))
		return sort_stdin();
	if (argc > 1 && !strcmp(argv[1], "test"))
		return run_tests(argc - 2, argv + 2);
	fprintf(stderr, "usage: test-tool mergesort sort\n");
	fprintf(stderr, "   or: test-tool mergesort test [<n>...]\n");
	return 129;
}