c++ - 吞吐量网络估计

Question

我如何估计瞬时吞吐量？例如，以类似于浏览器在下载文件时所做的方式。这不仅仅是平均吞吐量，而是瞬时估计，可能带有“移动平均数”。我正在寻找算法，但您可以在 C++ 中指定它。理想情况下，它不会涉及线程(即持续刷新，比如说每秒)，而是仅在询问值时才进行评估。

Answer 1

您可以使用指数移动平均线，如 here 所述，但我会重复这个公式:

accumulator = (alpha * new_value) + (1.0 - alpha) * accumulator

为了实现估算，假设您打算每秒查询一次计算，但您想要最后一分钟的平均值。那么，这里是获得该估计值的一种方法:

struct AvgBps {
    double rate_;            // The average rate
    double last_;            // Accumulates bytes added until average is computed
    time_t prev_;            // Time of previous update
    AvgBps () : rate_(0), last_(0), prev_(time(0)) {}
    void add (unsigned bytes) {
        time_t now = time(0);
        if (now - prev_ < 60) {       // The update is within the last minute
            last_ += bytes;           // Accumulate bytes into last
            if (now > prev_) {        // More than a second elapsed from previous
                // exponential moving average
                // the more time that has elapsed between updates, the more
                // weight is assigned for the accumulated bytes
                double alpha = (now - prev_)/60.0;
                rate_ = (1 -alpha) * last_ + alpha * rate_;
                last_ = 0;            // Reset last_ (it has been averaged in)
                prev_ = now;          // Update prev_ to current time
            }
        } else {                      // The update is longer than a minute ago
            rate_ = bytes;            // Current update is average rate
            last_ = 0;                // Reset last_
            prev_ = now;              // Update prev_
        }
    }
    double rate () {
        add(0);                       // Compute rate by doing an update of 0 bytes
        return rate_;                 // Return computed rate
    }
};

您实际上应该使用单调时钟而不是 time。