runtime: adjust expected error threshold in TestSelectFairness
Make it a bit more relaxed on the expected fairness, as fastrand()
isn't a truly perfect random number generator.
Fixes #34808
Change-Id: Ib55b2bbe3c1bf63fb4f446fd1291eb1236efc33b
Reviewed-on: https://go-review.googlesource.com/c/go/+/200857
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/runtime/chan_test.go b/src/runtime/chan_test.go
index f5a7a57..d4752dd 100644
--- a/src/runtime/chan_test.go
+++ b/src/runtime/chan_test.go
@@ -480,11 +480,11 @@
// If the select in the goroutine is fair,
// cnt1 and cnt2 should be about the same value.
// With 10,000 trials, the expected margin of error at
- // a confidence level of five nines is 4.4172 / (2 * Sqrt(10000)).
+ // a confidence level of six nines is 4.891676 / (2 * Sqrt(10000)).
r := float64(cnt1) / trials
e := math.Abs(r - 0.5)
t.Log(cnt1, cnt2, r, e)
- if e > 4.4172/(2*math.Sqrt(trials)) {
+ if e > 4.891676/(2*math.Sqrt(trials)) {
t.Errorf("unfair select: in %d trials, results were %d, %d", trials, cnt1, cnt2)
}
close(done)
