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Merge branch 'sg/bisect-approximately-halfway' 

"git bisect start/next" in a large span of history spends a lot of
time trying to come up with exactly the half-way point; this can be
optimized by stopping when we see a commit that is close enough to
the half-way point.

* sg/bisect-approximately-halfway:
  bisect: loosen halfway() check for a large number of commits
maint
Junio C Hamano 2020-11-25 15:24:52 -08:00
parent fd6445a0b8 0afcea70b1
commit 2557c1183a
1 changed files with 20 additions and 7 deletions
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27
bisect.c
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@ -103,8 +103,10 @@ static int count_interesting_parents(struct commit *commit, unsigned bisect_flag
return count; return count;
} }


static inline int halfway(struct commit_list *p, int nr) static inline int approx_halfway(struct commit_list *p, int nr)
{ {
int diff;

/* /*
* Don't short-cut something we are not going to return! * Don't short-cut something we are not going to return!
*/ */
@ -113,13 +115,22 @@ static inline int halfway(struct commit_list *p, int nr)
if (DEBUG_BISECT) if (DEBUG_BISECT)
return 0; return 0;
/* /*
* 2 and 3 are halfway of 5. * For small number of commits 2 and 3 are halfway of 5, and
* 3 is halfway of 6 but 2 and 4 are not. * 3 is halfway of 6 but 2 and 4 are not.
*/ */
switch (2 * weight(p) - nr) { diff = 2 * weight(p) - nr;
switch (diff) {
case -1: case 0: case 1: case -1: case 0: case 1:
return 1; return 1;
default: default:
/*
* For large number of commits we are not so strict, it's
* good enough if it's within ~0.1% of the halfway point,
* e.g. 5000 is exactly halfway of 10000, but we consider
* the values [4996, 5004] as halfway as well.
*/
if (abs(diff) < nr / 1024)
return 1;
return 0; return 0;
} }
} }
@ -321,8 +332,9 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
weight_set(p, count_distance(p)); weight_set(p, count_distance(p));
clear_distance(list); clear_distance(list);


/* Does it happen to be at exactly half-way? */ /* Does it happen to be at half-way? */
if (!(bisect_flags & FIND_BISECTION_ALL) && halfway(p, nr)) if (!(bisect_flags & FIND_BISECTION_ALL) &&
approx_halfway(p, nr))
return p; return p;
counted++; counted++;
} }
@ -362,8 +374,9 @@ static struct commit_list *do_find_bisection(struct commit_list *list,
else else
weight_set(p, weight(q)); weight_set(p, weight(q));


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