message: avoid divide by zero, limits user weight to EPSILON
diff: @@ -73,6 +73,10 @@ impl ServerStat {
  const SCORE_FAIL_WEIGHT: f64 = 3.0;
  const SCORE_STDEV_WEIGHT: f64 = 1.0;
  + // [EPSILON, 1]
  + // Just for avoiding divide by 0
  + let user_weight = self.user_weight.max(f32::EPSILON);
  +
  // Score = (norm_lat * 1.0 + prop_err * 3.0 + stdev * 1.0) / 5.0 / user_weight
  //
  // 1. The lower latency, the better
  @@ -81,7 +85,7 @@ impl ServerStat {
  // 4. The higher user's weight, the better
  let score = (nrtt * SCORE_RTT_WEIGHT + self.fail_rate * SCORE_FAIL_WEIGHT + nstdev * SCORE_STDEV_WEIGHT)
  / (SCORE_RTT_WEIGHT + SCORE_FAIL_WEIGHT + SCORE_STDEV_WEIGHT)
  - / self.user_weight as f64;
  + / user_weight as f64;
  // Times 10000 converts to u32, for 0.0001 precision
  (score * 10000.0) as u32
  