PHP – rand(1,1000)= 1000可能与rand(1,1000)= rand(1,1000)？
发布时间：2020-12-13 18:18:41 所属栏目：PHP教程 来源：网络整理
导读：这是 PHP实现随机数生成的方式吗？ 说我想计算是或否.每次我都有一定的概率百分比(例如：这个例子为0,05％). 我做： $possibilities = 100 / $probabilityPercentage; //$possibilities = 2000$yes = rand(1,$possibilities);$yesCheck = $possiblities; //O
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这是
PHP实现随机数生成的方式吗？
说我想计算是或否.每次我都有一定的概率百分比(例如：这个例子为0,05％). 我做： $possibilities = 100 / $probabilityPercentage; //$possibilities = 2000 $yes = rand(1,$possibilities); $yesCheck = $possiblities; //OPTION 1 $yesCheck = rand(1,$possibilities); //OPTION 2 ($yesCheck == $yes) ? return true : return false; 两种方案都能给出相同的结果吗？
让数据说明一切.
码 vinko@parrot:~$more rand.php
<?php
$randrandsum = 0;
$randconstsum = 0;
$count = 20;
for ($j = 0; $j < $count; $j++) {
$randrand = 0;
$randconst = 0;
for ($i = 0; $i < 10000000; $i++ ){
$a = rand(1,1000);
$b = rand(1,1000);
if ($a == $b) $randrand++;
}
for ($i = 0; $i < 10000000; $i++ ){
$a = rand(1,1000);
$c = 1000;
if ($c == $a) $randconst++;
}
$randrandsum += $randrand;
$randconstsum += $randconst;
print ($j+1)." RAND-RAND: $randrand RAND-CONST: $randconstn";
}
print "AVG RAND-RAND: ".($randrandsum/$count);
print " AVG RAND-CONST: ".($randconstsum/$count)."n";
?>
测试运行 vinko@parrot:~$php rand.php 1 RAND-RAND: 10043 RAND-CONST: 10018 2 RAND-RAND: 9940 RAND-CONST: 10132 3 RAND-RAND: 9879 RAND-CONST: 10042 4 RAND-RAND: 9878 RAND-CONST: 9965 5 RAND-RAND: 10226 RAND-CONST: 9867 6 RAND-RAND: 9866 RAND-CONST: 9992 7 RAND-RAND: 10069 RAND-CONST: 9953 8 RAND-RAND: 9967 RAND-CONST: 9862 9 RAND-RAND: 10009 RAND-CONST: 10060 10 RAND-RAND: 9809 RAND-CONST: 9985 11 RAND-RAND: 9939 RAND-CONST: 10057 12 RAND-RAND: 9945 RAND-CONST: 10013 13 RAND-RAND: 10090 RAND-CONST: 9936 14 RAND-RAND: 10000 RAND-CONST: 9867 15 RAND-RAND: 10055 RAND-CONST: 10088 16 RAND-RAND: 10129 RAND-CONST: 9875 17 RAND-RAND: 9846 RAND-CONST: 10056 18 RAND-RAND: 9961 RAND-CONST: 9930 19 RAND-RAND: 10063 RAND-CONST: 10001 20 RAND-RAND: 10047 RAND-CONST: 10037 AVG RAND-RAND: 9988.05 AVG RAND-CONST: 9986.8 鉴于上述结果,我会说,出于所有实际目的,两个选项都是等价的,给出了两种情况下预期的1/1000结果. （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |