test: make map nan timing test more robust

take 2

R=rsc
CC=golang-dev
https://golang.org/cl/5617045

diff --git a/test/map.go b/test/map.go
index a92586ff4aeedfd08614e5677f3b6c06421ea762..215e56c7f64de8ba5db97187bbed69acee6fbc12 100644 (file)
--- a/test/map.go
+++ b/test/map.go
@@ -667,10 +667,25 @@ func testnan() {
                return time.Since(t0)
        }
 
-       n := 60000 // 0.04 seconds on a MacBook Air
-       t1 := t(n)
-       t2 := t(2 * n)
-       if t2 > 3*t1 { // should be 2x (linear); allow up to 3x
-               fmt.Printf("too slow: %d inserts: %v; %d inserts: %v\n", n, t1, 2*n, t2)
+       // Depending on the machine and OS, this test might be too fast
+       // to measure with accurate enough granularity. On failure,
+       // make it run longer, hoping that the timing granularity
+       // is eventually sufficient.
+
+       n := 30000 // 0.02 seconds on a MacBook Air
+       fails := 0
+       for {
+               t1 := t(n)
+               t2 := t(2 * n)
+               // should be 2x (linear); allow up to 3x
+               if t2 < 3*t1 {
+                       return
+               }
+               fails++
+               if fails == 4 {
+                       fmt.Printf("too slow: %d inserts: %v; %d inserts: %v\n", n, t1, 2*n, t2)
+                       return
+               }
+               n *= 2
        }
 }