threads / patch / 828

patchdiffcore-break.c: various fixes.

Subject: [PATCH] diffcore-break.c: various fixes.

## tl;dr

2 messages between Jun 4, 2005 and Jun 5, 2005. Diffs are folded; open one to read it.

replies: 1people: 2as markdown or json

Junio C Hamano· Jun 4, 2005, 06:05 UTC · lore
This fixes three bugs in the -B heuristics.
 - Although it was advertised that the initial break criteria
   used was the same as what diffcore-rename uses, it was using
   something different.  Instead of using smaller of src and dst
   size to compare with "edit" size, (insertion and deletion),
   it was using larger of src and dst, unlike the rename/copy
   detection logic.  This caused the parameter to -B to mean
   something different from the one to -M and -C.  To compensate
   for this change, the default break score is also changed to
   match that of the default for rename/copy.
 - The code would have crashed with division by zero when trying
   to break an originally empty file.
 - Contrary to what the comment said, the algorithm was breaking
   small files, only to later merge them together.
Signed-off-by: Junio C Hamano <junkio@cox.net>
---
 diffcore.h       |    2 +-
 diffcore-break.c |   22 ++++++++--------------
 2 files changed, 9 insertions(+), 15 deletions(-)
Show changes to 2 files +9 −15

diffcore.h, diffcore-break.c

diff --git a/diffcore.h b/diffcore.h
--- a/diffcore.h
+++ b/diffcore.h
@@ -17,7 +17,7 @@
  */
 #define MAX_SCORE 60000
 #define DEFAULT_RENAME_SCORE 30000 /* rename/copy similarity minimum (50%) */
-#define DEFAULT_BREAK_SCORE  59400 /* minimum for break to happen (99%)*/
+#define DEFAULT_BREAK_SCORE  30000 /* minimum for break to happen (50%)*/
 #define DEFAULT_MERGE_SCORE  48000 /* maximum for break-merge to happen (80%)*/
 
 #define MINIMUM_BREAK_SIZE     400 /* do not break a file smaller than this */
diff --git a/diffcore-break.c b/diffcore-break.c
--- a/diffcore-break.c
+++ b/diffcore-break.c
@@ -61,14 +61,7 @@ static int should_break(struct diff_file
 	if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
 		return 0; /* error but caught downstream */
 
-	delta_size = ((src->size < dst->size) ?
-		      (dst->size - src->size) : (src->size - dst->size));
-
-	/* Notice that we use max of src and dst as the base size,
-	 * unlike rename similarity detection.  This is so that we do
-	 * not mistake a large addition as a complete rewrite.
-	 */
-	base_size = ((src->size < dst->size) ? dst->size : src->size);
+	base_size = ((src->size < dst->size) ? src->size : dst->size);
 
 	delta = diff_delta(src->data, src->size,
 			   dst->data, dst->size,
@@ -88,10 +81,11 @@ static int should_break(struct diff_file
 	 * less than the minimum, after rename/copy runs.
 	 */
 	if (src->size <= src_copied)
-		delta_size = 0; /* avoid wrapping around */
-	else
+		; /* all copied, nothing removed */
+	else {
 		delta_size = src->size - src_copied;
-	*merge_score_p = delta_size * MAX_SCORE / src->size;
+		*merge_score_p = delta_size * MAX_SCORE / src->size;
+	}
 	
 	/* Extent of damage, which counts both inserts and
 	 * deletes.
@@ -174,7 +168,8 @@ void diffcore_break(int break_score)
 		    !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) &&
 		    !strcmp(p->one->path, p->two->path)) {
 			if (should_break(p->one, p->two,
-					 break_score, &score)) {
+					 break_score, &score) &&
+			    MINIMUM_BREAK_SIZE <= p->one->size) {
 				/* Split this into delete and create */
 				struct diff_filespec *null_one, *null_two;
 				struct diff_filepair *dp;
@@ -185,8 +180,7 @@ void diffcore_break(int break_score)
 				 * Also we do not want to break very
 				 * small files.
 				 */
-				if ((score < merge_score) ||
-				    (p->one->size < MINIMUM_BREAK_SIZE))
+				if (score < merge_score)
 					score = 0;
 
 				/* deletion of one */
------------
Petr Baudis· Jun 5, 2005, 20:40 UTC · re: Junio C Hamano · lore

Re: [PATCH] diff.c: locate_size_cache() fix.

Show 12 quoted lines
> This fixes two bugs.
> 
>  - declaration of auto variable "cmp" was preceeded by a
>    statement, causing compilation error on real C compilers;
>    noticed and patch given by Yoichi Yuasa.
> 
>  - the function's calling convention was overloading its size
>    parameter to mean "largest possible value means do not add
>    entry", which was a bad taste.  Brought up during a
>    discussion with Peter Baudis.
> 
> Signed-off-by: Junio C Hamano <junkio@cox.net>
Show 5 quoted lines
> This fixes a bug that was preventing non-default parameter to -B
> option to be passed correctly; you could not give more than 50%
> break score.
> 
> Signed-off-by: Junio C Hamano <junkio@cox.net>
Show 19 quoted lines
> This fixes three bugs in the -B heuristics.
> 
>  - Although it was advertised that the initial break criteria
>    used was the same as what diffcore-rename uses, it was using
>    something different.  Instead of using smaller of src and dst
>    size to compare with "edit" size, (insertion and deletion),
>    it was using larger of src and dst, unlike the rename/copy
>    detection logic.  This caused the parameter to -B to mean
>    something different from the one to -M and -C.  To compensate
>    for this change, the default break score is also changed to
>    match that of the default for rename/copy.
> 
>  - The code would have crashed with division by zero when trying
>    to break an originally empty file.
> 
>  - Contrary to what the comment said, the algorithm was breaking
>    small files, only to later merge them together.
> 
> Signed-off-by: Junio C Hamano <junkio@cox.net>
  Hello,
  what's up with those three fixes? Were they pointed out to be wrong
and thrown away in another thread, are they on hold or just dropped?
Should I just apply them to git-pb?
  Thanks,
-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
C++: an octopus made by nailing extra legs onto a dog. -- Steve Taylor

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