package main

import (
	"fmt"
	"runtime"
	"sync"
	"time"
)

func main() {
	fmt.Printf("当前Go版本：%s\n", runtime.Version())
	// 设置P的数量为2
	runtime.GOMAXPROCS(1)
	// 再获取当前值
	fmt.Printf("CPU 核心数: %d, GOMAXPROCS: %d\n", runtime.NumCPU(), runtime.GOMAXPROCS(-1))
	var wg sync.WaitGroup
	startTime := time.Now()

	// 创建4个CPU密集型任务
	for i := 0; i < 4; i++ {
		wg.Add(1)
		go func(id int) {
			defer wg.Done()
			// 模拟CPU密集型计算
			sum := 0
			for j := 0; j < 1000000000; j++ {
				sum += j
			}
			fmt.Printf("任务%d 完成，耗时: %v\n", id, time.Since(startTime))
		}(i)
	}
	wg.Wait()
	fmt.Printf("总耗时: %v\n", time.Since(startTime))
}