讓CPU使用率按正弦變化

代碼取自《編程之美》

隨便找個編譯器就可以運行，比如Devcpp等

#include <stdlib.h>
#include <windows.h>
#include <math.h>
 
const int COUNT = 200;/* 把一個正弦週期平分成 COUNT 份 */
const double SPLIT = 2.0/COUNT;/* 用於後面計算sin值 */
const double PI = 3.1415926;
const int INTERVAL = 300;/* 一個採樣週期的時長 */
int main()
{    
    SetThreadAffinityMask(GetCurrentThread(), 2);/* 指定當前線程在哪個CPU上運行 */
 
    DWORD busySpan[COUNT];/* 記錄週期中的每一份的忙碌的時長 */
    DWORD idleSpan[COUNT];/* 記錄週期中的每一份的空閒的時長 */
    int half = INTERVAL / 2;
    double radian = 0.0;
    for (int i = 0; i < COUNT; ++i)
    {
/* 結合half進行運算是爲了向上平移正弦函數，保證非負的忙碌時長,且最大值爲INTERVAL */
        busySpan[i] = (DWORD)(half + sin(PI * radian) * half);
        idleSpan[i] = INTERVAL - busySpan[i];
        radian += SPLIT;
    }
 
    DWORD startTime = 0;
    int j = 0;
    while (true)
    {
        j = j % COUNT;
        startTime = GetTickCount();
        while (GetTickCount() - startTime <= busySpan[j]);
        Sleep(idleSpan[j]);
        j += 1;
    }
 
    return 0;
}

所以可以隨意操控CPU，不管是控制它一直50%還是90%，都可以，只要控制CPU的忙閒時間就好。

多核CPU同時變化

#include <iostream>
#include <windows.h>
#include <cmath>
#define PI 3.1415926535
using namespace std;
const double _1000MILLI = 1000;
void per_second_cpu(__int64 start_time,double busy_time_rate){
    start_time = GetTickCount();
    while ((GetTickCount() - start_time) <= busy_time_rate * _1000MILLI){}
    Sleep((1.0-busy_time_rate) * _1000MILLI);
}
void line_cpu( double busy_time_rate ){
    __int64 start_time;
    while(true){
        per_second_cpu(start_time,busy_time_rate);
    }
}
void sin_cpu(){
    __int64 start_time;
    while(true){
        int t = 15;
        for (int i = 0; i < t; ++i) {
            double busy_time_rate =  sin( i * 2 / ( t * 1.0 ) * PI ) / 2.0 + 0.5;
            per_second_cpu(start_time , busy_time_rate);
        }
    }
}
DWORD WINAPI handle_line(LPVOID lpParameter){
    line_cpu(*(double*)lpParameter);
}
DWORD WINAPI handle_sin(LPVOID lpParameter){
    sin_cpu();
}
void begin_line(double busy_time_rate){
    SetProcessAffinityMask(GetCurrentProcess(),255);
    for (int i = 0; i < 7; ++i) {
        HANDLE handleProcess = CreateThread(NULL, 0, handle_line, &busy_time_rate, 0, NULL);
        CloseHandle(handleProcess);
    }
    line_cpu(busy_time_rate);
}
void begin_sin(){
    SetProcessAffinityMask(GetCurrentProcess(),255);
    for (int i = 0; i < 7; ++i) {
        HANDLE handleProcess = CreateThread(NULL, 0, handle_sin, NULL, 0, NULL);
        CloseHandle(handleProcess);
    }
    sin_cpu();
}
int main() {
//    double busy_time_rate=0.5;
//    begin_line(busy_time_rate);
    begin_sin();
    return 0;
}