[thirdparty/git.git] / bisect.c

#include "cache.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
#include "sha1-lookup.h"
#include "bisect.h"

static unsigned char (*skipped_sha1)[20];
static int skipped_sha1_nr;

/* bits #0-15 in revision.h */

#define COUNTED		(1u<<16)

/*
 * This is a truly stupid algorithm, but it's only
 * used for bisection, and we just don't care enough.
 *
 * We care just barely enough to avoid recursing for
 * non-merge entries.
 */
static int count_distance(struct commit_list *entry)
{
	int nr = 0;

	while (entry) {
		struct commit *commit = entry->item;
		struct commit_list *p;

		if (commit->object.flags & (UNINTERESTING | COUNTED))
			break;
		if (!(commit->object.flags & TREESAME))
			nr++;
		commit->object.flags |= COUNTED;
		p = commit->parents;
		entry = p;
		if (p) {
			p = p->next;
			while (p) {
				nr += count_distance(p);
				p = p->next;
			}
		}
	}

	return nr;
}

static void clear_distance(struct commit_list *list)
{
	while (list) {
		struct commit *commit = list->item;
		commit->object.flags &= ~COUNTED;
		list = list->next;
	}
}

#define DEBUG_BISECT 0

static inline int weight(struct commit_list *elem)
{
	return *((int*)(elem->item->util));
}

static inline void weight_set(struct commit_list *elem, int weight)
{
	*((int*)(elem->item->util)) = weight;
}

static int count_interesting_parents(struct commit *commit)
{
	struct commit_list *p;
	int count;

	for (count = 0, p = commit->parents; p; p = p->next) {
		if (p->item->object.flags & UNINTERESTING)
			continue;
		count++;
	}
	return count;
}

static inline int halfway(struct commit_list *p, int nr)
{
	/*
	 * Don't short-cut something we are not going to return!
	 */
	if (p->item->object.flags & TREESAME)
		return 0;
	if (DEBUG_BISECT)
		return 0;
	/*
	 * 2 and 3 are halfway of 5.
	 * 3 is halfway of 6 but 2 and 4 are not.
	 */
	switch (2 * weight(p) - nr) {
	case -1: case 0: case 1:
		return 1;
	default:
		return 0;
	}
}

#if !DEBUG_BISECT
#define show_list(a,b,c,d) do { ; } while (0)
#else
static void show_list(const char *debug, int counted, int nr,
		      struct commit_list *list)
{
	struct commit_list *p;

	fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);

	for (p = list; p; p = p->next) {
		struct commit_list *pp;
		struct commit *commit = p->item;
		unsigned flags = commit->object.flags;
		enum object_type type;
		unsigned long size;
		char *buf = read_sha1_file(commit->object.sha1, &type, &size);
		char *ep, *sp;

		fprintf(stderr, "%c%c%c ",
			(flags & TREESAME) ? ' ' : 'T',
			(flags & UNINTERESTING) ? 'U' : ' ',
			(flags & COUNTED) ? 'C' : ' ');
		if (commit->util)
			fprintf(stderr, "%3d", weight(p));
		else
			fprintf(stderr, "---");
		fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
		for (pp = commit->parents; pp; pp = pp->next)
			fprintf(stderr, " %.*s", 8,
				sha1_to_hex(pp->item->object.sha1));

		sp = strstr(buf, "\n\n");
		if (sp) {
			sp += 2;
			for (ep = sp; *ep && *ep != '\n'; ep++)
				;
			fprintf(stderr, " %.*s", (int)(ep - sp), sp);
		}
		fprintf(stderr, "\n");
	}
}
#endif /* DEBUG_BISECT */

static struct commit_list *best_bisection(struct commit_list *list, int nr)
{
	struct commit_list *p, *best;
	int best_distance = -1;

	best = list;
	for (p = list; p; p = p->next) {
		int distance;
		unsigned flags = p->item->object.flags;

		if (flags & TREESAME)
			continue;
		distance = weight(p);
		if (nr - distance < distance)
			distance = nr - distance;
		if (distance > best_distance) {
			best = p;
			best_distance = distance;
		}
	}

	return best;
}

struct commit_dist {
	struct commit *commit;
	int distance;
};

static int compare_commit_dist(const void *a_, const void *b_)
{
	struct commit_dist *a, *b;

	a = (struct commit_dist *)a_;
	b = (struct commit_dist *)b_;
	if (a->distance != b->distance)
		return b->distance - a->distance; /* desc sort */
	return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
}

static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
{
	struct commit_list *p;
	struct commit_dist *array = xcalloc(nr, sizeof(*array));
	int cnt, i;

	for (p = list, cnt = 0; p; p = p->next) {
		int distance;
		unsigned flags = p->item->object.flags;

		if (flags & TREESAME)
			continue;
		distance = weight(p);
		if (nr - distance < distance)
			distance = nr - distance;
		array[cnt].commit = p->item;
		array[cnt].distance = distance;
		cnt++;
	}
	qsort(array, cnt, sizeof(*array), compare_commit_dist);
	for (p = list, i = 0; i < cnt; i++) {
		struct name_decoration *r = xmalloc(sizeof(*r) + 100);
		struct object *obj = &(array[i].commit->object);

		sprintf(r->name, "dist=%d", array[i].distance);
		r->next = add_decoration(&name_decoration, obj, r);
		p->item = array[i].commit;
		p = p->next;
	}
	if (p)
		p->next = NULL;
	free(array);
	return list;
}

/*
 * zero or positive weight is the number of interesting commits it can
 * reach, including itself.  Especially, weight = 0 means it does not
 * reach any tree-changing commits (e.g. just above uninteresting one
 * but traversal is with pathspec).
 *
 * weight = -1 means it has one parent and its distance is yet to
 * be computed.
 *
 * weight = -2 means it has more than one parent and its distance is
 * unknown.  After running count_distance() first, they will get zero
 * or positive distance.
 */
static struct commit_list *do_find_bisection(struct commit_list *list,
					     int nr, int *weights,
					     int find_all)
{
	int n, counted;
	struct commit_list *p;

	counted = 0;

	for (n = 0, p = list; p; p = p->next) {
		struct commit *commit = p->item;
		unsigned flags = commit->object.flags;

		p->item->util = &weights[n++];
		switch (count_interesting_parents(commit)) {
		case 0:
			if (!(flags & TREESAME)) {
				weight_set(p, 1);
				counted++;
				show_list("bisection 2 count one",
					  counted, nr, list);
			}
			/*
			 * otherwise, it is known not to reach any
			 * tree-changing commit and gets weight 0.
			 */
			break;
		case 1:
			weight_set(p, -1);
			break;
		default:
			weight_set(p, -2);
			break;
		}
	}

	show_list("bisection 2 initialize", counted, nr, list);

	/*
	 * If you have only one parent in the resulting set
	 * then you can reach one commit more than that parent
	 * can reach.  So we do not have to run the expensive
	 * count_distance() for single strand of pearls.
	 *
	 * However, if you have more than one parents, you cannot
	 * just add their distance and one for yourself, since
	 * they usually reach the same ancestor and you would
	 * end up counting them twice that way.
	 *
	 * So we will first count distance of merges the usual
	 * way, and then fill the blanks using cheaper algorithm.
	 */
	for (p = list; p; p = p->next) {
		if (p->item->object.flags & UNINTERESTING)
			continue;
		if (weight(p) != -2)
			continue;
		weight_set(p, count_distance(p));
		clear_distance(list);

		/* Does it happen to be at exactly half-way? */
		if (!find_all && halfway(p, nr))
			return p;
		counted++;
	}

	show_list("bisection 2 count_distance", counted, nr, list);

	while (counted < nr) {
		for (p = list; p; p = p->next) {
			struct commit_list *q;
			unsigned flags = p->item->object.flags;

			if (0 <= weight(p))
				continue;
			for (q = p->item->parents; q; q = q->next) {
				if (q->item->object.flags & UNINTERESTING)
					continue;
				if (0 <= weight(q))
					break;
			}
			if (!q)
				continue;

			/*
			 * weight for p is unknown but q is known.
			 * add one for p itself if p is to be counted,
			 * otherwise inherit it from q directly.
			 */
			if (!(flags & TREESAME)) {
				weight_set(p, weight(q)+1);
				counted++;
				show_list("bisection 2 count one",
					  counted, nr, list);
			}
			else
				weight_set(p, weight(q));

			/* Does it happen to be at exactly half-way? */
			if (!find_all && halfway(p, nr))
				return p;
		}
	}

	show_list("bisection 2 counted all", counted, nr, list);

	if (!find_all)
		return best_bisection(list, nr);
	else
		return best_bisection_sorted(list, nr);
}

struct commit_list *find_bisection(struct commit_list *list,
					  int *reaches, int *all,
					  int find_all)
{
	int nr, on_list;
	struct commit_list *p, *best, *next, *last;
	int *weights;

	show_list("bisection 2 entry", 0, 0, list);

	/*
	 * Count the number of total and tree-changing items on the
	 * list, while reversing the list.
	 */
	for (nr = on_list = 0, last = NULL, p = list;
	     p;
	     p = next) {
		unsigned flags = p->item->object.flags;

		next = p->next;
		if (flags & UNINTERESTING)
			continue;
		p->next = last;
		last = p;
		if (!(flags & TREESAME))
			nr++;
		on_list++;
	}
	list = last;
	show_list("bisection 2 sorted", 0, nr, list);

	*all = nr;
	weights = xcalloc(on_list, sizeof(*weights));

	/* Do the real work of finding bisection commit. */
	best = do_find_bisection(list, nr, weights, find_all);
	if (best) {
		if (!find_all)
			best->next = NULL;
		*reaches = weight(best);
	}
	free(weights);
	return best;
}

static int skipcmp(const void *a, const void *b)
{
	return hashcmp(a, b);
}

static void prepare_skipped(void)
{
	qsort(skipped_sha1, skipped_sha1_nr, sizeof(*skipped_sha1), skipcmp);
}

static const unsigned char *skipped_sha1_access(size_t index, void *table)
{
	unsigned char (*skipped)[20] = table;
	return skipped[index];
}

static int lookup_skipped(unsigned char *sha1)
{
	return sha1_pos(sha1, skipped_sha1, skipped_sha1_nr,
			skipped_sha1_access);
}

struct commit_list *filter_skipped(struct commit_list *list,
				   struct commit_list **tried,
				   int show_all)
{
	struct commit_list *filtered = NULL, **f = &filtered;

	*tried = NULL;

	if (!skipped_sha1_nr)
		return list;

	prepare_skipped();

	while (list) {
		struct commit_list *next = list->next;
		list->next = NULL;
		if (0 <= lookup_skipped(list->item->object.sha1)) {
			/* Move current to tried list */
			*tried = list;
			tried = &list->next;
		} else {
			if (!show_all)
				return list;
			/* Move current to filtered list */
			*f = list;
			f = &list->next;
		}
		list = next;
	}

	return filtered;
}
Commit	Line	Data
a2ad79ce CC	1	#include "cache.h"
	2	#include "commit.h"
	3	#include "diff.h"
	4	#include "revision.h"
4eb5b646	5	#include "sha1-lookup.h"
a2ad79ce CC	6	#include "bisect.h"
a2ad79ce CC	7
95188648 CC	8	static unsigned char (*skipped_sha1)[20];
	9	static int skipped_sha1_nr;
	10
a2ad79ce CC	11	/* bits #0-15 in revision.h */
	12
	13	#define COUNTED (1u<<16)
	14
	15	/*
	16	* This is a truly stupid algorithm, but it's only
	17	* used for bisection, and we just don't care enough.
	18	*
	19	* We care just barely enough to avoid recursing for
	20	* non-merge entries.
	21	*/
	22	static int count_distance(struct commit_list *entry)
	23	{
	24	int nr = 0;
	25
	26	while (entry) {
	27	struct commit *commit = entry->item;
	28	struct commit_list *p;
	29
	30	if (commit->object.flags & (UNINTERESTING \| COUNTED))
	31	break;
	32	if (!(commit->object.flags & TREESAME))
	33	nr++;
	34	commit->object.flags \|= COUNTED;
	35	p = commit->parents;
	36	entry = p;
	37	if (p) {
	38	p = p->next;
	39	while (p) {
	40	nr += count_distance(p);
	41	p = p->next;
	42	}
	43	}
	44	}
	45
	46	return nr;
	47	}
	48
	49	static void clear_distance(struct commit_list *list)
	50	{
	51	while (list) {
	52	struct commit *commit = list->item;
	53	commit->object.flags &= ~COUNTED;
	54	list = list->next;
	55	}
	56	}
	57
	58	#define DEBUG_BISECT 0
	59
	60	static inline int weight(struct commit_list *elem)
	61	{
	62	return ((int)(elem->item->util));
	63	}
	64
	65	static inline void weight_set(struct commit_list *elem, int weight)
	66	{
	67	((int)(elem->item->util)) = weight;
	68	}
	69
	70	static int count_interesting_parents(struct commit *commit)
	71	{
	72	struct commit_list *p;
	73	int count;
	74
75	for (count = 0, p = commit->parents; p; p = p->next) {
76	if (p->item->object.flags & UNINTERESTING)
77	continue;
78	count++;
79	}
80	return count;
81	}
82
83	static inline int halfway(struct commit_list *p, int nr)
84	{
85	/*
86	* Don't short-cut something we are not going to return!
87	*/
88	if (p->item->object.flags & TREESAME)
89	return 0;
90	if (DEBUG_BISECT)
91	return 0;
92	/*
93	* 2 and 3 are halfway of 5.
94	* 3 is halfway of 6 but 2 and 4 are not.
95	*/
96	switch (2 * weight(p) - nr) {
97	case -1: case 0: case 1:
98	return 1;
99	default:
100	return 0;
101	}
102	}
103
104	#if !DEBUG_BISECT
105	#define show_list(a,b,c,d) do { ; } while (0)
106	#else
107	static void show_list(const char *debug, int counted, int nr,
108	struct commit_list *list)
109	{
110	struct commit_list *p;
111
112	fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
113
114	for (p = list; p; p = p->next) {
115	struct commit_list *pp;
116	struct commit *commit = p->item;
117	unsigned flags = commit->object.flags;
118	enum object_type type;
119	unsigned long size;
120	char *buf = read_sha1_file(commit->object.sha1, &type, &size);
121	char ep, sp;
122
123	fprintf(stderr, "%c%c%c ",
124	(flags & TREESAME) ? ' ' : 'T',
125	(flags & UNINTERESTING) ? 'U' : ' ',
126	(flags & COUNTED) ? 'C' : ' ');
127	if (commit->util)
128	fprintf(stderr, "%3d", weight(p));
129	else
130	fprintf(stderr, "---");
131	fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
132	for (pp = commit->parents; pp; pp = pp->next)
133	fprintf(stderr, " %.*s", 8,
134	sha1_to_hex(pp->item->object.sha1));
135
136	sp = strstr(buf, "\n\n");
137	if (sp) {
138	sp += 2;
139	for (ep = sp; ep && ep != '\n'; ep++)
140	;
141	fprintf(stderr, " %.*s", (int)(ep - sp), sp);
142	}
143	fprintf(stderr, "\n");
144	}
145	}
146	#endif /* DEBUG_BISECT */
147
148	static struct commit_list best_bisection(struct commit_list list, int nr)
149	{
150	struct commit_list p, best;
151	int best_distance = -1;
152
153	best = list;
154	for (p = list; p; p = p->next) {
155	int distance;
156	unsigned flags = p->item->object.flags;
157
158	if (flags & TREESAME)
159	continue;
160	distance = weight(p);
161	if (nr - distance < distance)
162	distance = nr - distance;
163	if (distance > best_distance) {
164	best = p;
165	best_distance = distance;
166	}
167	}
168
169	return best;
170	}
171
172	struct commit_dist {
173	struct commit *commit;
174	int distance;
175	};
176
177	static int compare_commit_dist(const void a_, const void b_)
178	{
179	struct commit_dist a, b;
180
181	a = (struct commit_dist *)a_;
182	b = (struct commit_dist *)b_;
183	if (a->distance != b->distance)
184	return b->distance - a->distance; /* desc sort */
185	return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
186	}
187
188	static struct commit_list best_bisection_sorted(struct commit_list list, int nr)
189	{
190	struct commit_list *p;
191	struct commit_dist array = xcalloc(nr, sizeof(array));
192	int cnt, i;
193
194	for (p = list, cnt = 0; p; p = p->next) {
195	int distance;
196	unsigned flags = p->item->object.flags;
197
198	if (flags & TREESAME)
199	continue;
200	distance = weight(p);
201	if (nr - distance < distance)
202	distance = nr - distance;
203	array[cnt].commit = p->item;
204	array[cnt].distance = distance;
205	cnt++;
206	}
207	qsort(array, cnt, sizeof(*array), compare_commit_dist);
208	for (p = list, i = 0; i < cnt; i++) {
209	struct name_decoration r = xmalloc(sizeof(r) + 100);
210	struct object *obj = &(array[i].commit->object);
211
212	sprintf(r->name, "dist=%d", array[i].distance);
213	r->next = add_decoration(&name_decoration, obj, r);
214	p->item = array[i].commit;
215	p = p->next;
216	}
217	if (p)
218	p->next = NULL;
219	free(array);
220	return list;
221	}
222
223	/*
224	* zero or positive weight is the number of interesting commits it can
225	* reach, including itself. Especially, weight = 0 means it does not
226	* reach any tree-changing commits (e.g. just above uninteresting one
227	* but traversal is with pathspec).
228	*
229	* weight = -1 means it has one parent and its distance is yet to
230	* be computed.
231	*
232	* weight = -2 means it has more than one parent and its distance is
233	* unknown. After running count_distance() first, they will get zero
234	* or positive distance.
235	*/
236	static struct commit_list do_find_bisection(struct commit_list list,
237	int nr, int *weights,
238	int find_all)
239	{
240	int n, counted;
241	struct commit_list *p;
242
243	counted = 0;
244
245	for (n = 0, p = list; p; p = p->next) {
246	struct commit *commit = p->item;
247	unsigned flags = commit->object.flags;
248
249	p->item->util = &weights[n++];
250	switch (count_interesting_parents(commit)) {
251	case 0:
252	if (!(flags & TREESAME)) {
253	weight_set(p, 1);
254	counted++;
255	show_list("bisection 2 count one",
256	counted, nr, list);
257	}
258	/*
259	* otherwise, it is known not to reach any
260	* tree-changing commit and gets weight 0.
261	*/
262	break;
263	case 1:
264	weight_set(p, -1);
265	break;
266	default:
267	weight_set(p, -2);
268	break;
269	}
270	}
271
272	show_list("bisection 2 initialize", counted, nr, list);
273
274	/*
275	* If you have only one parent in the resulting set
276	* then you can reach one commit more than that parent
277	* can reach. So we do not have to run the expensive
278	* count_distance() for single strand of pearls.
279	*
280	* However, if you have more than one parents, you cannot
281	* just add their distance and one for yourself, since
282	* they usually reach the same ancestor and you would
283	* end up counting them twice that way.
284	*
285	* So we will first count distance of merges the usual
286	* way, and then fill the blanks using cheaper algorithm.
287	*/
288	for (p = list; p; p = p->next) {
289	if (p->item->object.flags & UNINTERESTING)
290	continue;
291	if (weight(p) != -2)
292	continue;
293	weight_set(p, count_distance(p));
294	clear_distance(list);
295
296	/* Does it happen to be at exactly half-way? */
297	if (!find_all && halfway(p, nr))
298	return p;
299	counted++;
300	}
301
302	show_list("bisection 2 count_distance", counted, nr, list);
303
304	while (counted < nr) {
305	for (p = list; p; p = p->next) {
306	struct commit_list *q;
307	unsigned flags = p->item->object.flags;
308
309	if (0 <= weight(p))
310	continue;
311	for (q = p->item->parents; q; q = q->next) {
312	if (q->item->object.flags & UNINTERESTING)
313	continue;
314	if (0 <= weight(q))
315	break;
316	}
317	if (!q)
318	continue;
319
320	/*
321	* weight for p is unknown but q is known.
322	* add one for p itself if p is to be counted,
323	* otherwise inherit it from q directly.
324	*/
325	if (!(flags & TREESAME)) {
326	weight_set(p, weight(q)+1);
327	counted++;
328	show_list("bisection 2 count one",
329	counted, nr, list);
330	}
331	else
332	weight_set(p, weight(q));
333
334	/* Does it happen to be at exactly half-way? */
335	if (!find_all && halfway(p, nr))
336	return p;
337	}
338	}
339
340	show_list("bisection 2 counted all", counted, nr, list);
341
342	if (!find_all)
343	return best_bisection(list, nr);
344	else
345	return best_bisection_sorted(list, nr);
346	}
347
348	struct commit_list find_bisection(struct commit_list list,
349	int reaches, int all,
350	int find_all)
351	{
352	int nr, on_list;
353	struct commit_list p, best, next, last;
354	int *weights;
355
356	show_list("bisection 2 entry", 0, 0, list);
357
358	/*
359	* Count the number of total and tree-changing items on the
360	* list, while reversing the list.
361	*/
362	for (nr = on_list = 0, last = NULL, p = list;
363	p;
364	p = next) {
365	unsigned flags = p->item->object.flags;
366
367	next = p->next;
368	if (flags & UNINTERESTING)
369	continue;
370	p->next = last;
371	last = p;
372	if (!(flags & TREESAME))
373	nr++;
374	on_list++;
375	}
376	list = last;
377	show_list("bisection 2 sorted", 0, nr, list);
378
379	*all = nr;
380	weights = xcalloc(on_list, sizeof(*weights));
381
382	/* Do the real work of finding bisection commit. */
383	best = do_find_bisection(list, nr, weights, find_all);
384	if (best) {
385	if (!find_all)
386	best->next = NULL;
387	*reaches = weight(best);
388	}
389	free(weights);
390	return best;
391	}
392
95188648 CC	393	static int skipcmp(const void a, const void b)
	394	{
	395	return hashcmp(a, b);
	396	}
	397
	398	static void prepare_skipped(void)
	399	{
	400	qsort(skipped_sha1, skipped_sha1_nr, sizeof(*skipped_sha1), skipcmp);
	401	}
	402
4eb5b646 CC	403	static const unsigned char skipped_sha1_access(size_t index, void table)
	404	{
	405	unsigned char (*skipped)[20] = table;
	406	return skipped[index];
	407	}
	408
95188648 CC	409	static int lookup_skipped(unsigned char *sha1)
95188648 CC	410	{
4eb5b646 CC	411	return sha1_pos(sha1, skipped_sha1, skipped_sha1_nr,
4eb5b646 CC	412	skipped_sha1_access);
95188648 CC	413	}
	414
	415	struct commit_list filter_skipped(struct commit_list list,
	416	struct commit_list **tried,
	417	int show_all)
	418	{
	419	struct commit_list filtered = NULL, *f = &filtered;
	420
	421	*tried = NULL;
	422
	423	if (!skipped_sha1_nr)
	424	return list;
	425
	426	prepare_skipped();
	427
	428	while (list) {
	429	struct commit_list *next = list->next;
	430	list->next = NULL;
	431	if (0 <= lookup_skipped(list->item->object.sha1)) {
	432	/* Move current to tried list */
	433	*tried = list;
	434	tried = &list->next;
	435	} else {
	436	if (!show_all)
	437	return list;
	438	/* Move current to filtered list */
	439	*f = list;
	440	f = &list->next;
	441	}
	442	list = next;
	443	}
	444
	445	return filtered;
	446	}