Adding upstream version 1.17.13.upstream/1.17.13upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 56 insertions, 0 deletions

diff --git a/test/chan/sieve1.go b/test/chan/sieve1.go
new file mode 100644
index 0000000..acc310f
--- /dev/null
+++ b/test/chan/sieve1.go
@@ -0,0 +1,56 @@
+// run
+
+// Copyright 2009 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 concurrency primitives: classical inefficient concurrent prime sieve.
+
+// Generate primes up to 100 using channels, checking the results.
+// This sieve consists of a linear chain of divisibility filters,
+// equivalent to trial-dividing each n by all primes p ≤ n.
+
+package main
+
+// Send the sequence 2, 3, 4, ... to channel 'ch'.
+func Generate(ch chan<- int) {
+	for i := 2; ; i++ {
+		ch <- i // Send 'i' to channel 'ch'.
+	}
+}
+
+// Copy the values from channel 'in' to channel 'out',
+// removing those divisible by 'prime'.
+func Filter(in <-chan int, out chan<- int, prime int) {
+	for i := range in { // Loop over values received from 'in'.
+		if i%prime != 0 {
+			out <- i // Send 'i' to channel 'out'.
+		}
+	}
+}
+
+// The prime sieve: Daisy-chain Filter processes together.
+func Sieve(primes chan<- int) {
+	ch := make(chan int) // Create a new channel.
+	go Generate(ch)      // Start Generate() as a subprocess.
+	for {
+		// Note that ch is different on each iteration.
+		prime := <-ch
+		primes <- prime
+		ch1 := make(chan int)
+		go Filter(ch, ch1, prime)
+		ch = ch1
+	}
+}
+
+func main() {
+	primes := make(chan int)
+	go Sieve(primes)
+	a := []int{2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97}
+	for i := 0; i < len(a); i++ {
+		if x := <-primes; x != a[i] {
+			println(x, " != ", a[i])
+			panic("fail")
+		}
+	}
+}