--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/twice.go	Tue Jan 30 14:26:41 2018 +0900
@@ -0,0 +1,52 @@
+package main
+
+import (
+    "flag"
+    "fmt"
+    "runtime"
+    "time"
+)
+
+func twice(list []int, prefix int, index int, c chan []int) {
+    for i := 0; i < prefix; i++ {
+        list[prefix*index+i] = list[prefix*index+i] * 2;
+    }
+    c <- list
+}
+
+func main() {
+    length := flag.Int("l", 1024, "length")
+    split := flag.Int("s", 8, "task size")
+    cpu := flag.Int("cpu", 1, "cpu")
+    flag.Parse()
+
+    fmt.Println("length: ", *length);
+    prefix := *length / *split
+    fmt.Println("length/task: ", prefix);
+    fmt.Println("cpu :", *cpu);
+
+    list := []int{};
+    for i :=0; i < *length; i++ {
+        list = append(list, i);
+    }
+
+    runtime.GOMAXPROCS(*cpu)
+
+    c := make(chan []int)
+    start := time.Now()
+    for i :=0; i < *split; i++ {
+        go twice(list, prefix, i, c);
+    }
+
+    for i :=0; i < *split; i++ {
+        <- c
+    }
+    t := time.Now()
+    elapsed := t.Sub(start)
+    fmt.Println(elapsed)
+    for i :=0; i < *length; i++ {
+        if (i*2 != list[i]) {
+            fmt.Println("wrong result")
+        }
+    }
+}