From: NeilBrown <neil@brown.name>
Date: Mon, 7 Sep 2020 09:40:52 +0000 (+1000)
Subject: Test must not expose non-determinism.
X-Git-Tag: v1.3~8
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=2802d9aa1927e133f9827716088bea3d47edeefe;p=wiggle.git

Test must not expose non-determinism.

The recent heuristic to make 'diff' faster introduce non-determinism
which is bad for testing.

So add option to set the loop count rather than having a maximum running
time.

Signed-off-by: NeilBrown <neil@brown.name>
---

diff --git a/diff.c b/diff.c
index 31d77db..954d3d6 100644
--- a/diff.c
+++ b/diff.c
@@ -178,9 +178,17 @@ static int find_common(struct file *a, struct file *b,
 	 */
 	int worst = (ahi-alo)+(bhi-blo);
 
+	int loopcount = -1;
 	shortcut = !!shortcut;
-	if (shortcut)
-		gettimeofday(&start, NULL);
+	if (shortcut) {
+		char *lc = getenv("WIGGLE_LOOPCOUNT");
+		if (lc)
+			loopcount = atoi(lc);
+		if (loopcount < 5) {
+			loopcount = -1;
+			gettimeofday(&start, NULL);
+		}
+	}
 
 	klo = khi = alo-blo;
 	v[klo].x = alo;
@@ -191,11 +199,15 @@ static int find_common(struct file *a, struct file *b,
 		int cost;
 		int k;
 
+		if (loopcount > 0)
+			loopcount -= 1;
 		if (shortcut == 1 &&
 		    khi - klo > 5000 &&
-		    gettimeofday(&stop, NULL) == 0 &&
-		    (stop.tv_sec - start.tv_sec) * 1000000 +
-		    (stop.tv_usec - start.tv_usec) > 20000)
+		    (loopcount == 0 ||
+		     (loopcount < 0 &&
+		      gettimeofday(&stop, NULL) == 0 &&
+		      (stop.tv_sec - start.tv_sec) * 1000000 +
+		      (stop.tv_usec - start.tv_usec) > 20000)))
 			/* 20ms is a long time.  Time to take a shortcut
 			 * Next snake wins
 			 */
diff --git a/dotest b/dotest
index e718f13..1b3a44e 100755
--- a/dotest
+++ b/dotest
@@ -38,6 +38,9 @@ status=0
 ok=0
 fail=0
 
+# Avoid non-determinism cause by CPU speed
+export WIGGLE_LOOPCOUNT=5000
+
 find . -name core | xargs rm -f
 list=$(find . -type f \( -name script -o -name diff -o -name ldiff \
 	-o -name rediff -o -name merge -o -name wmerge -o -name lmerge \