public static function resetAll($retain_benchmarks = array())
  {
    // If no benchmarks should be retained
    if (count($retain_benchmarks) == 0)
    {
      self::$benchmark_results = array();
      return;
    }
    
    // Else reset all benchmarks BUT the retain_benachmarks
    @reset(self::$benchmark_results);
    while (list($identifier) = @each(self::$benchmark_results))
    {
      if (!in_array($identifier, $retain_benchmarks))
      {
        self::$benchmark_results[$identifier] = 0;
      }
    }
  }