My c++ program spend so much CPU? - c++

Question

I have a project that I tried to run and it wasted more than 30% CPU. why?
The code is for a shortcut program and some reminders.
I am using visual studio 2017 c++ windows 10 Core Intel/i7
the command line:
/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
the code:
#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() is very processor intensive, as it's a tight loop.
As a crude fix, consider a Sleep on that thread too.

Answer 2

The correct way to find out is with a profiller; visual studio has one built in which you should get some practice with; since it would not only highlight your high CPU; but also which thread.
Knowing which thread, in this example, would be enough information to answer your question. If you plan to write threaded code you should get to grips with more of the tools in VS since threading gets very complex, very fast.