1 files changed, 64 insertions, 0 deletions
diff --git a/test/mapnan.go b/test/mapnan.go
new file mode 100644
index 000000000..60b35fbea
--- /dev/null
+++ b/test/mapnan.go
@@ -0,0 +1,64 @@
+// +build darwin linux
+// run
+
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that NaNs in maps don't go quadratic.
+
+package main
+
+import (
+	"fmt"
+	"math"
+	"time"
+	"syscall"
+)
+
+func main() {
+
+	// Test that NaNs in maps don't go quadratic.
+	t := func(n int) time.Duration {
+		var u0 syscall.Rusage
+		if err := syscall.Getrusage(0,  &u0); err != nil {
+			panic(err)
+		}
+		m := map[float64]int{}
+		nan := math.NaN()
+		for i := 0; i < n; i++ {
+			m[nan] = 1
+		}
+		if len(m) != n {
+			panic("wrong size map after nan insertion")
+		}
+		var u1 syscall.Rusage
+		if err := syscall.Getrusage(0,  &u1); err != nil {
+			panic(err)
+		}
+		return time.Duration(u1.Utime.Nano() - u0.Utime.Nano())
+	}
+
+	// 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 // ~8ms user time on a Mid 2011 MacBook Air (1.8 GHz Core i7)
+	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 == 6 {
+			panic(fmt.Sprintf("too slow: %d inserts: %v; %d inserts: %v\n", n, t1, 2*n, t2))
+		}
+		if fails < 4 {
+			n *= 2
+		}
+	}
+}