From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 9 Apr 2008 07:46:40 +0000 (-0700)
Subject: Merge branch 'jc/rename'
X-Git-Tag: v1.5.6-rc0~154
X-Git-Url: https://git.lorimer.id.au/gitweb.git/diff_plain/2a5fe2545882721d6841bad11dae0f15b454bf0d?ds=inline;hp=-c

Merge branch 'jc/rename'

* 'jc/rename' (early part):
Optimize rename detection for a huge diff
---

2a5fe2545882721d6841bad11dae0f15b454bf0d
diff --combined diffcore-rename.c
index 31941bcbbf,5974362d3b..1369a5ec45
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@@ -112,8 -112,8 +112,8 @@@ static int basename_same(struct diff_fi
  struct diff_score {
  	int src; /* index in rename_src */
  	int dst; /* index in rename_dst */
- 	int score;
- 	int name_score;
+ 	unsigned short score;
+ 	short name_score;
  };
  
  static int estimate_similarity(struct diff_filespec *src,
@@@ -223,6 -223,12 +223,12 @@@ static int score_compare(const void *a_
  {
  	const struct diff_score *a = a_, *b = b_;
  
+ 	/* sink the unused ones to the bottom */
+ 	if (a->dst < 0)
+ 		return (0 <= b->dst);
+ 	else if (b->dst < 0)
+ 		return -1;
+ 
  	if (a->score == b->score)
  		return b->name_score - a->name_score;
  
@@@ -387,6 -393,22 +393,22 @@@ static int find_exact_renames(void
  	return i;
  }
  
+ #define NUM_CANDIDATE_PER_DST 4
+ static void record_if_better(struct diff_score m[], struct diff_score *o)
+ {
+ 	int i, worst;
+ 
+ 	/* find the worst one */
+ 	worst = 0;
+ 	for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
+ 		if (score_compare(&m[i], &m[worst]) > 0)
+ 			worst = i;
+ 
+ 	/* is it better than the worst one? */
+ 	if (score_compare(&m[worst], o) > 0)
+ 		m[worst] = *o;
+ }
+ 
  void diffcore_rename(struct diff_options *options)
  {
  	int detect_rename = options->detect_rename;
@@@ -468,53 -490,66 +490,67 @@@
  	 */
  	if (rename_limit <= 0 || rename_limit > 32767)
  		rename_limit = 32767;
 -	if (num_create > rename_limit && num_src > rename_limit)
 -		goto cleanup;
 -	if (num_create * num_src > rename_limit * rename_limit)
 +	if ((num_create > rename_limit && num_src > rename_limit) ||
 +	    (num_create * num_src > rename_limit * rename_limit)) {
 +		warning("too many files, skipping inexact rename detection");
  		goto cleanup;
 +	}
  
- 	mx = xmalloc(sizeof(*mx) * num_create * num_src);
+ 	mx = xcalloc(num_create * NUM_CANDIDATE_PER_DST, sizeof(*mx));
  	for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
- 		int base = dst_cnt * num_src;
  		struct diff_filespec *two = rename_dst[i].two;
+ 		struct diff_score *m;
+ 
  		if (rename_dst[i].pair)
  			continue; /* dealt with exact match already. */
+ 
+ 		m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
+ 		for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
+ 			m[j].dst = -1;
+ 
  		for (j = 0; j < rename_src_nr; j++) {
  			struct diff_filespec *one = rename_src[j].one;
- 			struct diff_score *m = &mx[base+j];
- 			m->src = j;
- 			m->dst = i;
- 			m->score = estimate_similarity(one, two,
- 						       minimum_score);
- 			m->name_score = basename_same(one, two);
+ 			struct diff_score this_src;
+ 			this_src.score = estimate_similarity(one, two,
+ 							     minimum_score);
+ 			this_src.name_score = basename_same(one, two);
+ 			this_src.dst = i;
+ 			this_src.src = j;
+ 			record_if_better(m, &this_src);
  			diff_free_filespec_blob(one);
  		}
  		/* We do not need the text anymore */
  		diff_free_filespec_blob(two);
  		dst_cnt++;
  	}
+ 
  	/* cost matrix sorted by most to least similar pair */
- 	qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
- 	for (i = 0; i < num_create * num_src; i++) {
- 		struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
- 		struct diff_filespec *src;
+ 	qsort(mx, dst_cnt * NUM_CANDIDATE_PER_DST, sizeof(*mx), score_compare);
+ 
+ 	for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
+ 		struct diff_rename_dst *dst;
+ 
+ 		if ((mx[i].dst < 0) ||
+ 		    (mx[i].score < minimum_score))
+ 			break; /* there is no more usable pair. */
+ 		dst = &rename_dst[mx[i].dst];
  		if (dst->pair)
  			continue; /* already done, either exact or fuzzy. */
- 		if (mx[i].score < minimum_score)
- 			break; /* there is no more usable pair. */
- 		src = rename_src[mx[i].src].one;
- 		if (src->rename_used)
+ 		if (rename_src[mx[i].src].one->rename_used)
  			continue;
  		record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
  		rename_count++;
  	}
- 	for (i = 0; i < num_create * num_src; i++) {
- 		struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
+ 
+ 	for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
+ 		struct diff_rename_dst *dst;
+ 
+ 		if ((mx[i].dst < 0) ||
+ 		    (mx[i].score < minimum_score))
+ 			break; /* there is no more usable pair. */
+ 		dst = &rename_dst[mx[i].dst];
  		if (dst->pair)
  			continue; /* already done, either exact or fuzzy. */
- 		if (mx[i].score < minimum_score)
- 			break; /* there is no more usable pair. */
  		record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
  		rename_count++;
  	}