code: public function chart()
      {
          $result = '';
  
          $ranking = $this->_benchmark->matrix()->ranking();
  
          $maxLength = 0;
  
          $maxRate = 0;
  
          foreach($ranking as $task) {
              if ($task->failed()) {
                  continue;
              }
              if ($task->rate() > $maxRate){
                  $maxRate = $task->rate();
              }
              if (mb_strlen($task->name()) > $maxLength){
                  $maxLength = mb_strlen($task->name());
              }
          }
  
          foreach($ranking as $task) {
              $name = $task->name();
              $result .= $this->mb_str_pad($name, $maxLength, ' ', STR_PAD_RIGHT);
  
              if ($task->failed()) {
                  $ratio = 0;
                  $result .= $this->mb_str_pad('x', 10);
              } else {
                  $rate = $task->rate();
                  $ratio = ($rate / $maxRate);
                  $result .= $this->mb_str_pad(round($ratio*100) . '%', 10);
              }
              $result .= ' | ';
  
              $width = 60;
              $chars = (int) ($width * $ratio);
              $result .= str_repeat('█', $chars);
              $result .= str_repeat(' ', $width - $chars );
              $result .= "  |\n";
          }
          return $result;
      }
docs: Returns the bar chart.
  
  @return string The bar chart.