From: Junio C Hamano <gitster@pobox.com>
Date: Thu, 2 Jul 2009 02:41:04 +0000 (-0700)
Subject: Merge branch 'cc/bisect'
X-Git-Tag: v1.6.4-rc0~24
X-Git-Url: https://git.lorimer.id.au/gitweb.git/diff_plain/702beb3af0531bae95ab559fff043785614d53f2?hp=-c

Merge branch 'cc/bisect'

* cc/bisect:
Documentation: remove warning saying that "git bisect skip" may slow bisection
bisect: use a PRNG with a bias when skipping away from untestable commits
---

702beb3af0531bae95ab559fff043785614d53f2
diff --combined bisect.c
index dbeb28752a,095b55eba6..52220df751
--- a/bisect.c
+++ b/bisect.c
@@@ -454,7 -454,7 +454,7 @@@ static int read_bisect_refs(void
  	return for_each_ref_in("refs/bisect/", register_ref, NULL);
  }
  
 -void read_bisect_paths(struct argv_array *array)
 +static void read_bisect_paths(struct argv_array *array)
  {
  	struct strbuf str = STRBUF_INIT;
  	const char *filename = git_path("BISECT_NAMES");
@@@ -585,16 -585,49 +585,49 @@@ struct commit_list *filter_skipped(stru
  	return filtered;
  }
  
- static struct commit_list *apply_skip_ratio(struct commit_list *list,
- 					    int count,
- 					    int skip_num, int skip_denom)
+ #define PRN_MODULO 32768
+ 
+ /*
+  * This is a pseudo random number generator based on "man 3 rand".
+  * It is not used properly because the seed is the argument and it
+  * is increased by one between each call, but that should not matter
+  * for this application.
+  */
+ int get_prn(int count) {
+ 	count = count * 1103515245 + 12345;
+ 	return ((unsigned)(count/65536) % PRN_MODULO);
+ }
+ 
+ /*
+  * Custom integer square root from
+  * http://en.wikipedia.org/wiki/Integer_square_root
+  */
+ static int sqrti(int val)
+ {
+ 	float d, x = val;
+ 
+ 	if (val == 0)
+ 		return 0;
+ 
+ 	do {
+ 		float y = (x + (float)val / x) / 2;
+ 		d = (y > x) ? y - x : x - y;
+ 		x = y;
+ 	} while (d >= 0.5);
+ 
+ 	return (int)x;
+ }
+ 
+ static struct commit_list *skip_away(struct commit_list *list, int count)
  {
- 	int index, i;
  	struct commit_list *cur, *previous;
+ 	int prn, index, i;
+ 
+ 	prn = get_prn(count);
+ 	index = (count * prn / PRN_MODULO) * sqrti(prn) / sqrti(PRN_MODULO);
  
  	cur = list;
  	previous = NULL;
- 	index = count * skip_num / skip_denom;
  
  	for (i = 0; cur; cur = cur->next, i++) {
  		if (i == index) {
@@@ -614,7 -647,6 +647,6 @@@ static struct commit_list *managed_skip
  					   struct commit_list **tried)
  {
  	int count, skipped_first;
- 	int skip_num, skip_denom;
  
  	*tried = NULL;
  
@@@ -626,11 -658,7 +658,7 @@@
  	if (!skipped_first)
  		return list;
  
- 	/* Use alternatively 1/5, 2/5 and 3/5 as skip ratio. */
- 	skip_num = count % 3 + 1;
- 	skip_denom = 5;
- 
- 	return apply_skip_ratio(list, count, skip_num, skip_denom);
+ 	return skip_away(list, count);
  }
  
  static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
@@@ -780,7 -808,7 +808,7 @@@ static void handle_bad_merge_base(void
  	exit(1);
  }
  
 -void handle_skipped_merge_base(const unsigned char *mb)
 +static void handle_skipped_merge_base(const unsigned char *mb)
  {
  	char *mb_hex = sha1_to_hex(mb);
  	char *bad_hex = sha1_to_hex(current_bad_sha1);