1 // Concurrent computation of pi. 2 // See https://goo.gl/la6Kli. 3 // 4 // This demonstrates Go's ability to handle 5 // large numbers of concurrent processes. 6 // It is an unreasonable way to calculate pi. 7 package main 8 9 import ( 10 "fmt" 11 "math" 12 ) 13 14 func main() { 15 fmt.Println(pi(5000)) 16 } 17 18 // pi launches n goroutines to compute an 19 // approximation of pi. 20 func pi(n int) float64 { 21 ch := make(chan float64) 22 for k := 0; k <= n; k++ { 23 go term(ch, float64(k)) 24 } 25 f := 0.0 26 for k := 0; k <= n; k++ { 27 f += <-ch 28 } 29 return f 30 } 31 32 func term(ch chan float64, k float64) { 33 ch <- 4 * math.Pow(-1, k) / (2*k + 1) 34 } 35
