讓工作管理員進行繪圖

興之所致，找來一個有趣面試題目來解答：如何能讓CPU 的使用率表現為一條正弦曲線？

這個題目來自《编程之美--微软技术面试心得》，有機會的我會話買下來當作娛樂。

// This program try to burn cpu cycles with a sinusoid function against the time.
#include <MCD/Core/System/TaskPool.h>
#include <MCD/Core/System/Timer.h>
#include <math.h>

class Task : public MCD::TaskPool::Task {
public:
  Task(float frequency) : MCD::TaskPool::Task(0), mFrequency(frequency) {}

  sal_override void run(MCD::Thread& thread) throw() {
    MCD::Timer timer;
    while(thread.keepRun()) {
      double current = timer.get().asSecond();
      double busy = (sin(current * mFrequency) + 1) / 2;
      double idle = 1 - busy;  // We base on a 1 second interval
      while(timer.get().asSecond() < current + busy) {}  // Burn CPU cycles
      MCD::mSleep(int(idle * 1000));  // Let CPU idle
    }

    // The Task instance is not needed any more, destroy it.
    delete this;
  }

  float mFrequency;
};  // Task

int main(int, char const*[])
{
  const size_t cpuCount = 4;  // Set this to match your hardware thread count
  const float frequency = 0.1f;

  MCD::TaskPool taskPool;
  taskPool.setThreadCount(cpuCount);

  for(size_t i=0; i<cpuCount; ++i)
    taskPool.enqueue(*new Task(frequency));

  std::cout << "Press enter to quit...\n";
  std::cin.get();

  taskPool.stop();

  return 0;
}

註：中間的那個高峰因突如其來的 MSN 短訊耗掉了整整一個 CPU Core 而缺了一角。