Question

我正在读一本书，我给了一些计时器实现。然而，书中的计时器没有真正的解释，我想知道他为什么做某些事情。

代码：

//  Desc:   Use this class to regulate code flow (for an update function say)
//          Instantiate the class with the frequency you would like your code
//          section to flow (like 10 times per second) and then only allow 
//          the program flow to continue if Ready() returns true

class Regulator
{
private:

  //the time period between updates 
  double m_dUpdatePeriod;

  //the next time the regulator allows code flow
  DWORD m_dwNextUpdateTime;


public:


  Regulator(double NumUpdatesPerSecondRqd)
  {
    m_dwNextUpdateTime = (DWORD)(timeGetTime()+RandFloat()*1000);

    if (NumUpdatesPerSecondRqd > 0)
    {
      m_dUpdatePeriod = 1000.0 / NumUpdatesPerSecondRqd; 
    }

    else if (isEqual(0.0, NumUpdatesPerSecondRqd))
    {
      m_dUpdatePeriod = 0.0;
    }

    else if (NumUpdatesPerSecondRqd < 0)
    {
      m_dUpdatePeriod = -1;
    }
  }


  //returns true if the current time exceeds m_dwNextUpdateTime
  bool isReady()
  {
    //if a regulator is instantiated with a zero freq then it goes into
    //stealth mode (doesn't regulate)
    if (isEqual(0.0, m_dUpdatePeriod)) return true;

    //if the regulator is instantiated with a negative freq then it will
    //never allow the code to flow
    if (m_dUpdatePeriod < 0) return false;

    DWORD CurrentTime = timeGetTime();

    //the number of milliseconds the update period can vary per required
    //update-step. This is here to make sure any multiple clients of this class
    //have their updates spread evenly
    static const double UpdatePeriodVariator = 10.0;

    if (CurrentTime >= m_dwNextUpdateTime)
    {
      m_dwNextUpdateTime = (DWORD)(CurrentTime + m_dUpdatePeriod + RandInRange(-UpdatePeriodVariator, UpdatePeriodVariator));

      return true;
    }

    return false;
  }
};

isEqual()检查两个给定双打之间的差异是否小于0.00 ... 1

RandInRange()返回给定范围内的随机数

我真的不明白他为什么要在m_dwNextUpdateTime添加给定范围的随机数。即使他“解释”，但对我来说似乎没有任何意义。

有人可以帮忙吗？

Answer 1

// This is here to make sure any multiple clients of this class
//have their updates spread evenly

当您同时多次运行相同的代码时，会引入随机性以降低争用。如果所有客户使用完全相同的间隔，他们可能会全部醒来＆＃34;在同一时间，这可能是不幸的负载。引入一些随机变化使他们更多地展开他们的活动。

为什么要根据随机值更新计时器？

1 个答案: