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一个有趣的问题，对于 Uni 课程的一部分，我们面临着运行模拟服务器接收请求然后处理它们的挑战。我已经多次构建和重建了它，我认为它已经尽可能高效了，你有什么可以提高这个程序的效率的吗？

模拟运行，$simulationLength并且每次$currentTime都有1/$arrival_rate新请求到达的机会。一个大小的队列$maxQueueSize保存这些请求，如果队列已满，则拒绝它们。对于每个$currentTimeCPU 可能会从队列中移除一个项目$queue并在其上工作$executionTime几秒钟，此时 CPU（服务器）从繁忙队列中移除并且可以自由地处理另一个请求。

我的代码：

<?php

...SNIP error checking...

$queue_size = isset($argv[1]) ? $argv[1] : 10000;
$arrival_rate = isset($argv[2]) ? $argv[2] : 3;
$number_of_servers = isset($argv[3]) ? $argv[3] : 2;
$execution_time = isset($argv[4]) ? $argv[4] : 25;

...SNIP error checking...

$simulationLength = 1000000;

$arrivalRate = $arrival_rate;
$executionTime = $execution_time;

$busyServers = array();
$freeServers = $number_of_servers;

$currentTime = 0;
$currentQueueSize = 0;
$maxQueueSize = $queue_size; //Max
$queue = array();

//Stats
$totalRequests = 0;
$rejectedRequests = 0;
$queueSize = array_fill(0, 100, $simulationLength);
$totalWaitingTime = 0;

//while the simulation is running
while($currentTime++ < $simulationLength) {

  //a request has arrived
  if(mt_rand(1, $arrival_rate)==1) {  
    $totalRequests++;

    //Adding to the queue
    if($currentQueueSize < $maxQueueSize) {
      $currentQueueSize++;
      array_push($queue, $currentTime); //add to the end of the queue
    } else {
      $rejectedRequests++;
    }

  } //end request arrived

  //Only one server can fetch requests at a time
  if(!empty($busyServers)&&reset($busyServers) < $currentTime) {
    unset($busyServers[key($busyServers)]); //remove first element - efficient
    $freeServers++; //increase free servers
  }

  //Only one server can fetch requests at a time
  if($currentQueueSize>0&&$freeServers>1) {

    $currentQueueSize--;
    reset($queue); //reset pointer
    $queueTime = $queue[key($queue)]; //read of the front  
    unset($busyServers[key($busyServers)]); //delete off print

    $freeServers--; //use up a server

    $busyServers[] = $currentTime + $executionTime; //mark when free

    $totalWaitingTime += ($currentTime - $queueTime) + $executionTime;
  }

  $queueSize[$currentTime] = $currentQueueSize;
}

printf("Requests served %d\n", $totalRequests);
printf("Rejected requests %d\n", $rejectedRequests);
printf("Total waiting time %d\n", $totalWaitingTime);

printf("Percentage of rejected requests %0.1f\n", $rejectedRequests/$totalRequests);
printf("The average queue size %d\n", array_sum($queueSize)/sizeof($queueSize)); 
printf("Average response time %d\n", $totalWaitingTime/$totalRequests);

?>

谢谢你的时间，

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1 回答 1

1

微优化但：

  • 在像这样的繁重循环中，--$preIncrement 比 $postIncrement++ 快
  • array_push($queue, $currentTime); 是函数调用开销：使用 $queue[] = $currentTime; 反而
  • $currentTime + $executionTime 被计算两次，计算一次并存储结果，然后使用它
于 2012-04-18T21:48:35.183 回答