test/bench/go1: add mandelbrot for floating point

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6244063

diff --git a/test/bench/go1/mandel_test.go b/test/bench/go1/mandel_test.go
new file mode 100644 (file)
index 0000000..888c5e4
--- /dev/null
+++ b/test/bench/go1/mandel_test.go
@@ -0,0 +1,41 @@
+// Copyright 2012 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.
+
+// This benchmark, taken from the shootuot, tests floating point performance.
+
+package go1
+
+import "testing"
+
+func mandelbrot(n int) int {
+       const Iter = 50
+       const Zero float64 = 0
+       const Limit = 2.0
+       ok := 0
+       for y := 0; y < n; y++ {
+               for x := 0; x < n; x++ {
+                       Zr, Zi, Tr, Ti := Zero, Zero, Zero, Zero
+                       Cr := (2*float64(x)/float64(n) - 1.5)
+                       Ci := (2*float64(y)/float64(n) - 1.0)
+
+                       for i := 0; i < Iter && (Tr+Ti <= Limit*Limit); i++ {
+                               Zi = 2*Zr*Zi + Ci
+                               Zr = Tr - Ti + Cr
+                               Tr = Zr * Zr
+                               Ti = Zi * Zi
+                       }
+
+                       if Tr+Ti <= Limit*Limit {
+                               ok++
+                       }
+               }
+       }
+       return ok
+}
+
+func BenchmarkMandelbrot200(b *testing.B) {
+       for i := 0; i < b.N; i++ {
+               mandelbrot(200)
+       }
+}