Imported Upstream version 1upstream/1

1 files changed, 34 insertions, 0 deletions

diff --git a/doc/play/pi.go b/doc/play/pi.go
new file mode 100644
index 000000000..f2f5dca74
--- /dev/null
+++ b/doc/play/pi.go
@@ -0,0 +1,34 @@
+// Concurrent computation of pi.
+// See http://goo.gl/ZuTZM.
+//
+// This demonstrates Go's ability to handle
+// large numbers of concurrent processes.
+// It is an unreasonable way to calculate pi.
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+func main() {
+	fmt.Println(pi(5000))
+}
+
+// pi launches n goroutines to compute an
+// approximation of pi.
+func pi(n int) float64 {
+	ch := make(chan float64)
+	for k := 0; k <= n; k++ {
+		go term(ch, float64(k))
+	}
+	f := 0.0
+	for k := 0; k <= n; k++ {
+		f += <-ch
+	}
+	return f
+}
+
+func term(ch chan float64, k float64) {
+	ch <- 4 * math.Pow(-1, k) / (2*k + 1)
+}