Detailed explanation of performance test comparison examples of php function mt_rand() and rand()

The example in this article compares and analyzes the performance issues of random functions mt_rand() and rand() in PHP. Share it with everyone for your reference. The specific analysis is as follows:

In PHP, the mt_rand() and rand() functions can randomly generate a pure number. They both require us to set the seed data and then generate it. Then Which one of mt_rand() and rand() has better performance? Let’s test it with questions.

Example 1. mt_rand() example, the code is as follows:

<?php 
echo mt_rand() . "n"; 
echo mt_rand() . "n"; 
echo mt_rand(5, 15); 
?>

The results are as follows:

1604716014 
1478613278 
6

Note:Since PHP 4.2.0, it is no longer necessary to use the srand() or mt_srand() function to seed the random number generator, it is nowcompleted automatically.

Note:In versions before 3.0.7, max means range. To get the same random number from 5 to 15 as in the above example in these versions, a short example is mt_rand (5, 11).

For details, please refer to the relevant documents of mt_srand(), mt_getrandmax() and rand().

rand() function returns a random integer.

Syntax: rand(min,max)

说明:如果没有提供可选参数 min 和 max，rand() 返回 0 到 RAND_MAX 之间的伪随机整数,例如,想要 5 到 15(包括 5 和 15)之间的随机数,用 rand(5, 15).

提示和注释

注释:在某些平台下(例如 Windows)RAND_MAX 只有 32768,如果需要的范围大于 32768,那么指定 min 和 max 参数就可以生成大于 RAND_MAX 的数了,或者考虑用 mt_rand() 来替代它.

注释:自 PHP 4.2.0 起,不再需要用 srand() 或 mt_srand() 函数给随机数发生器播种,现在已自动完成.

注释:在 3.0.7 之前的版本中,max 的含义是 range,要在这些版本中得到和上例相同 5 到 15 的随机数,简短的例子是 rand (5, 11).

mt_rand()真的会比rand()快4倍吗？带着这个疑问一边自己测试一边看网上的介绍.测试如下.

mt_rand()和rand()对比测试一,测试代码如下:

<?php  
$max = 100000;  
$timeparts = explode(&#39; &#39;,microtime());  
$stime = $timeparts[1].substr($timeparts[0],1);  
$i = 0;  
while($i < $max) {  
rand();  
$i++;  
}  
$timeparts = explode(&#39; &#39;,microtime());  
$etime = $timeparts[1].substr($timeparts[0],1);  
$time = $etime-$stime;  
echo "{$max} random numbers generated in {$time} seconds using rand();"; 
 
$timeparts = explode(&#39; &#39;,microtime());  
$stime = $timeparts[1].substr($timeparts[0],1);  
$i = 0;  
while($i < $max) {  
mt_rand();  
$i++;  
}  
$timeparts = explode(&#39; &#39;,microtime());  
$etime = $timeparts[1].substr($timeparts[0],1);  
$time = $etime-$stime;  
echo "{$max} random numbers generated in {$time} seconds using mt_rand(); ";  
?>

测试结果如下：
//第一次测试
100000 random numbers generated in 0.024894952774048 seconds using rand();
100000 random numbers generated in 0.028925895690918 seconds using mt_rand();
//第二次测试
100000 random numbers generated in 0.03147292137146 seconds using rand();
100000 random numbers generated in 0.02997088432312 seconds using mt_rand();
//第三次测试
100000 random numbers generated in 0.028102874755859 seconds using rand();
100000 random numbers generated in 0.02803111076355 seconds using mt_rand();
//第四次测试
100000 random numbers generated in 0.025573015213013 seconds using rand();
100000 random numbers generated in 0.028030157089233 seconds using mt_rand();

这个结果只是几次的显示结果,多测试几次你会发觉,两者是交替变化的,其实两者没有太大的差异.

mt_rand()和rand()对比测试二

本人测试环境,操作系统:windows xp,apache 2.0,php 5.2.12,内存 2G

代码如下:

<?php  
function microtime_float()  
{  
    list($usec, $sec) = explode(" ", microtime());  
    return ((float)$usec + (float)$sec);  
}  
$time_start = microtime_float();  
for($i=0; $i<1000000; ++$i)  
{
    rand();  
}  
$time_end = microtime_float();  
$time = $time_end - $time_start;  
echo "rand() cost $time secondsn"; 
 
$time_start = microtime_float();  
for($i=0; $i<1000000; ++$i)  
{  
    mt_rand();  
}  
$time_end = microtime_float();  
$time = $time_end - $time_start;  
echo "mt_rand() cost $time secondsn";  
?>

测试结果如下：
//第一次
rand() cost 0.25919604301453 seconds
mt_rand() cost 0.28554391860962 seconds
//第二次
rand() cost 0.31136202812195 seconds
mt_rand() cost 0.28973197937012 seconds
//第三次
rand() cost 0.27545690536499 seconds
mt_rand() cost 0.27108001708984 seconds
//第四次
rand() cost 0.26263308525085 seconds
mt_rand() cost 0.27727103233337 seconds
结果还是一样:两者用的时间是交替变化,其实两者没有太大的差异.

php的mt_rand()与rand()对比结论

在网上看了很多别人的测试,有linux的还有windows环境的,大多数人得出的结果和我的一样:两者相差无几，不过也有人测出mt_rand()比rand()快4倍，但是由于他们没给出具体的测试环境，所以无法判断真假。我还是比较相信我的结论，因为我看到有人这样介绍mt_rand()与rand()：

那为什么php手册上说mt_rand()比rand()快4倍呢？

这是因为mt_rand()使用的Mersenne Twister algorythm是1997的事,所以在10年前,和rand()在速度上的差异是(4倍),自2004年,rand()已经开始使用algorythm,所以现在它们速度上没有太大的区别.

从上面的各种测试来看它们之间并没有区别,只是在不同系统中可能数值会有变化了.

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