我的c++程序花这么多CPU？

Question

我有一个项目，我尝试运行但它浪费了超过 30% CPU。为什么？

该代码用于快捷程序和一些提醒。

我正在使用 visual studio 2017 c++ windows 10 Core Intel/i7

命令行：

/Yu"stdafx.h" /GS /analyze- /W3 /Zc:wchar_t /ZI /Gm /Od /sdl /Fd"Debug\vc141.pdb" /Zc:inline /fp:precise /D "WIN32" /D "_DEBUG" /D "_CONSOLE" /D "_UNICODE" /D "UNICODE" /errorReport:prompt /WX- /Zc:forScope /RTC1 /Gd /Oy- /MDd / Fa"Debug\" /EHsc /nologo /Fo"Debug\" /Fp"Debug\Clear.pch" /diagnostics:classic

代码：

#include "stdafx.h"
#include <Windows.h>
#include <shellapi.h>

bool pressed(int key) { return GetAsyncKeyState(key); }
namespace Main {
///to hide the console
void Main()
{ 
            SetWindowPos(GetConsoleWindow(), nullptr, 0, 0, 0, 0, SWP_HIDEWINDOW);
}
///the shortcuts
void Main1() {
    while (true) {
        ///Win-C = chrome
        if (pressed(VK_LWIN)&&pressed('C')) system("chrome http://www.google.com");
        ///Menu = battery message
        if (pressed(VK_APPS)) {
            SYSTEM_POWER_STATUS a;
            GetSystemPowerStatus(&a);
            char title[15]; sprintf(title, "%d%% battery%s", a.BatteryLifePercent, a.BatteryFlag & 8 ? ", charging" : "");
            char disp[100]; sprintf(disp, "You have %d hours and %d minutes left...", a.BatteryLifeTime / 3600 % 60, a.BatteryLifeTime / 60 % 60);
            MessageBoxA(nullptr, disp, title, 0);
        }
        if (pressed(VK_LWIN) && pressed(VK_DELETE)) SHEmptyRecycleBinA(nullptr, "", 0);
        if (pressed(VK_LWIN) && pressed('V')) system("C:\Users\steven\source\repos\Clear\Clear.sln");
        if (pressed(VK_LWIN) && pressed('Z')) system("start cmd");
        Sleep(GetDoubleClickTime());
    }
}
///time
void Main2() {
    while (true) {
        SYSTEMTIME t;
        GetSystemTime(&t);
        if (t.wDayOfWeek != 4 && t.wDayOfWeek != 5 && t.wHour == 0 && t.wMinute == 0 && t.wSecond == 0 && t.wMilliseconds == 0) MessageBoxA(nullptr, "Its 00:00", "Sleep", 0);
        if (t.wDayOfWeek == 0 && t.wHour == 15 && t.wMinute == 10 && t.wSecond == 0 && t.wMilliseconds == 0) MessageBoxA(nullptr, "Go to the Technion", "תירגול", 0);
        if ((t.wDayOfWeek == 1 || t.wDayOfWeek == 2) && t.wHour == 12 && t.wMinute == 25 && t.wSecond == 0 && t.wMilliseconds == 0) MessageBoxA(nullptr, "Go to the lab", "Math is over", 0);
        if (t.wDayOfWeek == 3 && t.wHour == 9 && t.wMinute == 35 && t.wSecond == 0 && t.wMilliseconds == 0) MessageBoxA(nullptr, "Go to the class", "Math is over", 0);
        if (t.wDayOfWeek == 4 && t.wHour == 10 && t.wMinute == 50 && t.wSecond == 0 && t.wMilliseconds == 0) MessageBoxA(nullptr, "Go to the class", "Math is over", 0);
    }
}
///the exit shortcut
void Main0() {
    while (true) {
        if (pressed(VK_LMENU) && pressed(VK_RMENU)) if (MessageBoxA(nullptr, "Do you want to exit?", "ShortCut", MB_YESNO|MB_ICONINFORMATION) == IDYES) exit(0);
        Sleep(GetDoubleClickTime());
        }
    }
}
#include <thread>
using namespace std;
int main(){
using namespace Main;
thread a[4]={thread(Main), thread(Main0), thread(Main1), thread(Main2)};
for(thread& b:a) b.join();
return 0;}

Answer 1

Main2() 非常处理器密集型，因为它是一个紧凑的循环。

作为粗略的修复，也考虑在该线程上使用 Sleep。

Answer 2

正确的找出方法是使用 profiller； visual studio 有一个内置的，您应该练习一下；因为它不仅会突出你的高 CPU；还有哪个线程。

在此示例中，知道哪个线程就足以回答您的问题。如果您打算编写线程代码，您应该掌握 VS 中的更多工具，因为线程变得非常复杂、非常快。

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