golang设置CPU核数

众所周知，golang低版本需要自己手动设置CPU核数，才能保证并发的执行

packagemain

import(
	"errors"
	"fmt"
	"runtime"
	"strconv"
	"strings"
	"testing"
)

funcmain(){
	t:=&testing.T{}
	TestSetCPU(t)
}

funcTestSetCPU(t*testing.T){
	currentCPU:=runtime.GOMAXPROCS(-1)
	maxCPU:=runtime.NumCPU()
	halfCPU:=int(0.5*float32(maxCPU))
	ifhalfCPU<1{
		halfCPU=1
	}
	fori,test:=range[]struct{
		inputstring
		outputint
		shouldErrbool
	}{
		{"1",1,false},{"-1",currentCPU,true},{"0",{"100%",maxCPU,{"50%",halfCPU,{"110%",{"-10%",{"invalidinput",{"invalidinput%",{"9999",//overavailableCPU
	}{
		err:=setCPU(test.input)
		iftest.shouldErr&&err==nil{
			fmt.Printf("Test%d:Expectederror,buttherewasn'tany",i)
		}
		if!test.shouldErr&&err!=nil{
			fmt.Printf("Test%d:Expectednoerror,buttherewasone:%v",i,err)
		}
		ifactual,expected:=runtime.GOMAXPROCS(-1),test.output;actual!=expected{
			fmt.Printf("Test%d:GOMAXPROCSwas%dbutexpected%d",actual,expected)
		}else{
			fmt.Printf("--%v%vn",expected)
		}
		//teardown
		runtime.GOMAXPROCS(currentCPU)
	}
}

funcsetCPU(cpustring)error{
	varnumCPUint

	availCPU:=runtime.NumCPU()

	ifstrings.HasSuffix(cpu,"%"){
		//Percent
		varpercentfloat32
		pctStr:=cpu[:len(cpu)-1]
		pctInt,err:=strconv.Atoi(pctStr)
		iferr!=nil||pctInt<1||pctInt>100{
			returnerrors.New("invalidCPUvalue:percentagemustbebetween1-100")
		}
		percent=float32(pctInt)/100
		numCPU=int(float32(availCPU)*percent)
	}else{
		//Number
		num,err:=strconv.Atoi(cpu)
		iferr!=nil||num<1{
			returnerrors.New("invalidCPUvalue:provideanumberorpercentgreaterthan0")
		}
		numCPU=num
	}

	ifnumCPU>availCPU{
		numCPU=availCPU
	}

	runtime.GOMAXPROCS(numCPU)
	returnnil
}

关于golang的GOMAXPROCS的申明：

// GOMAXPROCS sets the maximum number of CPUs that can be executing

// simultaneously and returns the previous setting. If n < 1,it does not

// change the current setting.

// The number of logical CPUs on the local machine can be queried with NumCPU.

// This call will go away when the scheduler improves.

（编辑：李大同）

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