xdiff: simplify comparison

phillipwood · gitster · commit 6b13bc32322d · 2021-11-18T22:23:49.000-08:00
Now that the histogram algorithm calls xdl_classify_record() it is no
longer necessary to use xdl_recmatch() to compare lines, it is
sufficient just to compare the hash values. This has a negligible
effect on performance.

Test                                  HEAD~1            HEAD
-----------------------------------------------------------------------------
4000.1: log -3000 (baseline)          0.19(0.12+0.07)   0.18(0.14+0.04) -5.3%
4000.2: log --raw -3000 (tree-only)   0.98(0.81+0.16)   0.98(0.79+0.18) +0.0%
4000.3: log -p -3000 (Myers)          4.81(4.23+0.56)   4.80(4.26+0.53) -0.2%
4000.4: log -p -3000 --histogram      5.83(5.11+0.70)   5.82(5.15+0.65) -0.2%
4000.5: log -p -3000 --patience       5.31(4.61+0.69)   5.30(4.54+0.75) -0.2%

Signed-off-by: Phillip Wood &lt;phillip.wood@dunelm.org.uk&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
@@ -392,10 +392,7 @@ static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1,
 
 static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags)
 {
-	return (rec1->ha == rec2->ha &&
-		xdl_recmatch(rec1->ptr, rec1->size,
-			     rec2->ptr, rec2->size,
-			     flags));
+	return (rec1->ha == rec2->ha);
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -392,10 +392,7 @@ static xdchange_t xdl_add_change(xdchange_t xscr, long i1, long i2, long chg1,`
`392`	`392`
`393`	`393`	`static int recs_match(xrecord_t rec1, xrecord_t rec2, long flags)`
`394`	`394`	`{`
`395`		`- return (rec1->ha == rec2->ha &&`
`396`		`- xdl_recmatch(rec1->ptr, rec1->size,`
`397`		`- rec2->ptr, rec2->size,`
`398`		`- flags));`
	`395`	`+ return (rec1->ha == rec2->ha);`
`399`	`396`	`}`
`400`	`397`
`401`	`398`	`/*`