Question

首先，我创建了一个正则表达式，它将匹配项目中所有头文件列表中的所有唯一外部库路径。一周前I asked a question regarding making that regexp。

我开始干涉，看看它在异步和变成Web工作时的行为方式。为了方便和可靠，我创建了这个在所有三种模式下运行的通用文件：

/** Will call result() callback with every match it founds. Asynchronous unless called 
 *  with interval = -1.
 *  Javadoc style comment for Arnold Rimmer and other Java programmers:
 *  
 * @param regex regular expression to match in string
 * @param string guess what
 * @param result callback function that accepts one parameter, string match
 * @param done callback on finish, has no parameters
 * @param interval delay (not actual interval) between finding matches. If -1, 
 *        function  will be blocking
 * @property working false if loop isn't running, otherwise contains timeout ID
 *           for use with clearTimeout
 * @property done copy of done parameter
 * @throws heavy boulders
**/
function processRegex(regex, string, result, done, interval) {
  var m;
  //Please tell me interpreter optimizes this
  interval = typeof interval!='number'?1:interval;
  //And this
  processRegex.done = done;
  while ((m = regex.exec(string))) {
    Array.prototype.splice.call(m,0,1);
    var path = m.join("");
    //It's good to keep in mind that result() slows down the process
    result(path);
    if (interval>=0) {
      processRegex.working = setTimeout(processRegex, 
                              interval, regex, string, 
                              result, done, interval);
      // Comment these out for maximum speed
      processRegex.progress = regex.lastIndex/string.length;
      console.log("Progress: "+Math.round(processRegex.progress*100)+"%");
      return;
    }
  }

  processRegex.working = false;
  processRegex.done = null;
  if (typeof done=="function")
    done();
}
processRegex.working = false;

我创建了一个测试文件，而不是在此粘贴它，我将其上传到非常可靠的网络托管：Demo - Test data。

我发现非常令人惊讶的是，Web工作者和RegExp的浏览器执行之间存在如此显着的差异。我得到的结果是：

Mozilla Firefox
- [WORKER]: Time elapsed:16.860s
- [WORKER-SYNC]: Time elapsed:16.739s
- [TIMEOUT]: Time elapsed:5.186s
- [LOOP]: Time elapsed:5.028s

您还可以看到，使用我的特定正则表达式，同步和异步循环之间的差异是无关紧要的。我试图使用匹配列表而不是前瞻表达式，结果发生了很大变化。以下是旧功能的更改：

function processRegexUnique(regex, string, result, done, interval) {
  var matchList = arguments[5]||[];
  ... same as before ...
  while ((m = regex.exec(string))) {
    ... same as before ...
    if (matchList.indexOf(path)==-1) {
      result(path);
      matchList.push(path);
    }
    if (interval>=0) {
      processRegex.working = setTimeout(processRegex, interval, 
                               regex, string, result, 
                               done, interval, matchList);
      ... same as before ...
    }
  }
  ... same as before ...
}

结果：

Mozilla Firefox
- [WORKER]: Time elapsed:0.062s
- [WORKER-SYNC]: Time elapsed:0.023s
- [TIMEOUT]: Time elapsed:12.250s（自我注意：它每分钟都在变弱）
- [LOOP]: Time elapsed:0.006s

任何人都可以解释速度上的这种差异吗？

Answer 1

经过一系列测试，我确认这是一个 Mozilla Firefox 问题（它会影响我尝试的所有Windows桌面版本）。使用谷歌浏览器，Opera，甚至Firefox移动版，正则表达式匹配与工作者相同或不同。

如果您需要修复此问题，请务必在bug report on bugzilla上投票。如果有任何变化，我会尝试添加其他信息。

WebWorker计算慢速正则表达式匹配显着较慢（3x） - 仅限Firefox

1 个答案: