doc(example): add parallel merge sort example

examples/parallel_merge_sort/parallel_merge_sort.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"math/rand"
+	"os"
+	"slices"
+	"strconv"
+	"sync"
+
+	gtf "github.com/noneback/go-taskflow"
+)
+
+// meger sorted src to sorted dest
+func mergeInto(dest, src []int) []int {
+	size := len(dest) + len(src)
+	tmp := make([]int, 0, size)
+	i, j := 0, 0
+	for i < len(dest) && j < len(src) {
+		if dest[i] < src[j] {
+			tmp = append(tmp, dest[i])
+			i++
+		} else {
+			tmp = append(tmp, src[j])
+			j++
+		}
+	}
+
+	if i < len(dest) {
+		tmp = append(tmp, dest[i:]...)
+	} else {
+		tmp = append(tmp, src[j:]...)
+	}
+
+	return tmp
+}
+func main() {
+	size := 100
+	radomArr := make([][]int, 10)
+	sortedArr := make([]int, 0, 10*size)
+	mutex := &sync.Mutex{}
+
+	for i := 0; i < 10; i++ {
+		for j := 0; j < size; j++ {
+			radomArr[i] = append(radomArr[i], rand.Int())
+		}
+	}
+
+	sortTasks := make([]*gtf.Task, 10)
+	tf := gtf.NewTaskFlow("merge sort")
+	done := gtf.NewTask("Done", func() {
+		if !slices.IsSorted(sortedArr) {
+			log.Fatal("Failed")
+		}
+		fmt.Println("Sorted")
+		fmt.Println(sortedArr[:1000])
+	})
+
+	for i := 0; i < 10; i++ {
+		sortTasks[i] = gtf.NewTask("sort_"+strconv.Itoa(i), func() {
+			arr := radomArr[i]
+			slices.Sort(arr)
+			mutex.Lock()
+			defer mutex.Unlock()
+			sortedArr = mergeInto(sortedArr, arr)
+		})
+
+	}
+	done.Succeed(sortTasks...)
+	tf.Push(sortTasks...)
+	tf.Push(done)
+
+	executor := gtf.NewExecutor(1000)
+
+	executor.Run(tf).Wait()
+
+	if err := gtf.Visualize(tf, os.Stdout); err != nil {
+		log.Fatal("V->", err)
+	}
+
+	if err := executor.Profile(os.Stdout); err != nil {
+		log.Fatal("P->", err)
+	}
+
+}