shootout: make mandelbrot.go more like mandelbrot.c

Surprise! The C code is using floating point values for its counters.
Its off the critical path, but the Go code and C code are supposed to
be as similar as possible to make comparisons meaningful.

It doesn't have a significant effect.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6260058

diff --git a/test/bench/shootout/mandelbrot.go b/test/bench/shootout/mandelbrot.go
index 1f9fbfd3d4418345a603b53f0ab2f529755f13ee..df60343c240d453c41eab40dba0302863645adfe 100644 (file)
--- a/test/bench/shootout/mandelbrot.go
+++ b/test/bench/shootout/mandelbrot.go
@@ -50,21 +50,21 @@ func main() {
        out := bufio.NewWriter(os.Stdout)
        defer out.Flush()
 
-       w := *n
-       h := *n
+       w := float64(*n)
+       h := float64(*n)
        bit_num := 0
        byte_acc := byte(0)
        const Iter = 50
        const Zero float64 = 0
        const Limit = 2.0
 
-       fmt.Fprintf(out, "P4\n%d %d\n", w, h)
+       fmt.Fprintf(out, "P4\n%d %d\n", *n, *n)
 
-       for y := 0; y < h; y++ {
-               for x := 0; x < w; x++ {
+       for y := 0.0; y < h; y++ {
+               for x := 0.0; x < w; x++ {
                        Zr, Zi, Tr, Ti := Zero, Zero, Zero, Zero
-                       Cr := (2*float64(x)/float64(w) - 1.5)
-                       Ci := (2*float64(y)/float64(h) - 1.0)
+                       Cr := (2*x/w - 1.5)
+                       Ci := (2*y/h - 1.0)
 
                        for i := 0; i < Iter && (Tr+Ti <= Limit*Limit); i++ {
                                Zi = 2*Zr*Zi + Ci
@@ -85,7 +85,7 @@ func main() {
                                byte_acc = 0
                                bit_num = 0
                        } else if x == w-1 {
-                               byte_acc <<= uint(8 - w%8)
+                               byte_acc <<= uint(8 - uint(*n)%8)
                                out.WriteByte(byte_acc)
                                byte_acc = 0
                                bit_num = 0