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package like_fork_join
import (
"fmt"
"github.com/oklog/ulid/v2"
)
const defaultPageSize = 10
type MyForkJoinTask struct {
size int
}
// NewMyTask 初始化一个任务
func NewMyTask(pageSize int) *MyForkJoinTask {
var size = defaultPageSize
if pageSize > size {
size = pageSize
}
return &MyForkJoinTask{
size: size,
}
}
// Do 执行任务时，传入一个切片
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)
// 任务小于最小颗粒度时，直接执行逻辑（此处是求和），不再拆分，否则进行分治
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)
// 等待左边和右边分治子任务结束
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
}
}
// 取结果
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
}
}
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