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List of Big-O for PHP functions
After using PHP for a while now, I've noticed that not all built-in PHP functions are as fast as expected. Consider these two possible implementations of a function that finds if a number is prime using a cached array of primes.
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为什么一般逆时针旋转是拧松？ - 杂谈 - 清泛网 - 专注C/C++及内核技术
...恢复常态，闪过长达1秒钟的不好意思，就突然好奇这个问题了。
为什么是“逆时针→开，顺时针→关”？和左右手有关吗？和人体构造有关吗？
// 搜了搜原来这种无聊的问题还真的有人问过，中英文都有
右旋螺纹与右...
Linux下追踪程序退出(崩溃)思路 - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...命令。
Linux下程序退出(崩溃)时总会留下一些蛛丝马迹，问题追踪思路总结如下：
1、查看程序日志，确定退出(崩溃)时间。
2、coredumpctl查看是否有崩溃记录。
3、查看系统日志 cat /var/log/message，已切分压缩的日志使用 xzcat 查...
TokuMX vs. MongoDB 性能对比 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
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磁盘消耗对比：
选择MongoDB就必然会面对磁盘消耗的问题。我们拿到的数据大概是这样的：每天的数据量不到200万条，平均数据的大小不超过4k，但MongoDB存一个月的数据就需要接近40G，最近三个月的数据则需要接近100G。限...
关于jQuery的AJAX不兼容IE的解决办法 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...传了一点点数据。排除。
网上一些网友说是IE缓存的问题，在请求数据后边加上随机数就行，比如加上时间数new Date().getTime()。
先前的代码中我已经添加了随机数，用的是“Math.random()”也不行。难道用时间比较靠谱？
那...
Performance of foreach, array_map with lambda and array_map with static function
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FWIW, I just did the benchmark since poster didn't do it. Running on PHP 5.3.10 + XDebug.
UPDATE 2015-01-22 compare with mcfedr's answer below for additional results without XDebug and a more recent PHP version.
function lap($func) {
$t0 = microtime(1);
$numbers = range(0, 1000000);
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推荐系统算法初探 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...单，而且很多时候推荐也是很准确的。然而它也存在一些问题：
依赖于准确的用户评分；
在计算的过程中，那些大热的物品会有更大的几率被推荐给用户；
冷启动问题。当有一名新用户或者新物品进入系统时，推荐将无从依...
Unable to find the wrapper “https” - did you forget to enable it when you configured PHP?
...being said I'll list out exactly everything I've done so far. I am running PHP 5.2.14 with Zend Debugging on the latest Eclipse version on my Windows XP computer. I have a 1 GB of RAM. I have XAMPP running with Apache, MySQL, and FileZilla installed.
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Can't use method return value in write context
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empty() needs to access the value by reference (in order to check whether that reference points to something that exists), and PHP before 5.5 didn't support references to temporary values returned from functions.
However, the real problem you have is that you use empty() at ...
window.location.reload with clear cache [duplicate]
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