package like_fork_join
 
import (
    "fmt"
    "github.com/oklog/ulid/v2"
)
 
const defaultPageSize = 10
 
type MyForkJoinTask struct {
    size int
}
 
// NewMyTask 初始化一個任務
func NewMyTask(pageSize int) *MyForkJoinTask {
    var size = defaultPageSize
    if pageSize > size {
        size = pageSize
    }
    return &MyForkJoinTask{
        size: size,
    }
}
 
// Do 執(zhí)行任務時，傳入一個切片
func (t *MyForkJoinTask) Do(numbers []int) int {
    JoinCh := make(chan bool, 1)
    resultCh := make(chan int, 1)
    t.do(numbers, JoinCh, resultCh, ulid.Make().String())
    result := <-resultCh
    return result
}
 
func (t *MyForkJoinTask) do(numbers []int, joinCh chan bool, resultCh chan int, id string) {
    defer func() {
        joinCh <- true
        close(joinCh)
        close(resultCh)
    }()
    fmt.Printf("id %s numbers %+v\n", id, numbers)
    // 任務小于最小顆粒度時，直接執(zhí)行邏輯（此處是求和），不再拆分，否則進行分治
    if len(numbers) <= t.size {
        var sum = 0
        for _, number := range numbers {
            sum += number
        }
        resultCh <- sum
        fmt.Printf("id %s numbers %+v, result %+v\n", id, numbers, sum)
        return
    } else {
        start := 0
        end := len(numbers)
        middle := (start + end) / 2
 
        // 左
        leftJoinCh := make(chan bool, 1)
        leftResultCh := make(chan int, 1)
        leftId := ulid.Make().String()
        go t.do(numbers[start:middle], leftJoinCh, leftResultCh, id+"->left->"+leftId)
 
        // 右
        rightJoinCh := make(chan bool, 1)
        rightResultCh := make(chan int, 1)
        rightId := ulid.Make().String()
        go t.do(numbers[middle:], rightJoinCh, rightResultCh, id+"->right->"+rightId)
 
        // 等待左邊和右邊分治子任務結束
        var leftDone, rightDone = false, false
        for {
            select {
            case _, ok := <-leftJoinCh:
                if ok {
                    fmt.Printf("left %s join done\n", leftId)
                    leftDone = true
                }
            case _, ok := <-rightJoinCh:
                if ok {
                    fmt.Printf("right %s join done\n", rightId)
                    rightDone = true
                }
            }
            if leftDone && rightDone {
                break
            }
        }
 
        // 取結果
        var (
            left            = 0
            right           = 0
            leftResultDone  = false
            rightResultDone = false
        )
        for {
            select {
            case l, ok := <-leftResultCh:
                if ok {
                    fmt.Printf("id %s numbers %+v, left %s return: %+v\n", id, numbers, leftId, left)
                    left = l
                    leftResultDone = true
                }
            case r, ok := <-rightResultCh:
                if ok {
                    fmt.Printf("id %s numbers %+v, right %s return: %+v\n", id, numbers, rightId, right)
                    right = r
                    rightResultDone = true
                }
            }
            if leftResultDone && rightResultDone {
                break
            }
        }
 
        resultCh <- left + right
        return
    }
}

package like_fork_join
 
import (
    "fmt"
    "testing"
)
 
func TestMyTask_Do(t1 *testing.T) {
    type args struct {
        numbers []int
    }
    const max = 10000
    var nums = make([]int, 0, max)
    var want = 0
    for i := 1; i <= max; i++ {
        nums = append(nums, i)
        want += i
    }
    tests := []struct {
        name string
        args args
        want int
    }{
        {name: fmt.Sprintf("sum(1,%d)", max), args: args{numbers: nums}, want: want},
    }
    for _, tt := range tests {
        t1.Run(tt.name, func(t1 *testing.T) {
            for i := 0; i <= 100; i += 5 {
                t := NewMyTask(i)
                if got := t.Do(tt.args.numbers); got != tt.want {
                    t1.Errorf("Do() = %v, want %v", got, tt.want)
                }
            }
        })
    }
}

    --- PASS: TestMyTask_Do/sum(1,10000) (1257.79s)
PASS