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PHP と
乱打舞図
2014/03/15
第5回 闇PHP勉強会
do_aki
@do_aki
http://do-aki.net/
title was born from typo
らんだまいず
乱打舞図
モテカルロ法っぽくない?
randomize
• 無秩序に並び替えること
• 規則性がないこと
• 偏りがないこと
http://nmi.jp/archives/541
(http://www.lauradhamilton.com/random-
lessons-online-poker-exploit)
randomize function in php
shuffle
str_shuffle
give it try (php 5.5.10)
function bench($name, $suffle_func) {
$result = [];
for ($i=0; $i<60000;++$i) {
$a = range(1, 3);...
shuffle / str_shuffle
bench("shuffle", "shuffle");
bench("str_shuffle", function(&$ary) {
$str = str_shuffle(implode('', $...
result of shuffle
shuffle
Array
(
[123] => 9873
[132] => 10104
[213] => 9999
[231] => 9944
[312] => 9998
[321] => 10082
)
result of str_shuffle
str_shuffle
Array
(
[123] => 9956
[132] => 9928
[213] => 10080
[231] => 9969
[312] => 10149
[321] =>...
No Problem
(in current
version of php)
過去の shuffle は等分散ではなかった
implementation of shuffle(current version)
long n_elems, rnd_idx, n_left;
char temp;
/* The implementation is stolen from ...
implementation of shuffle (php < 4.3.0)
PHP_FUNCTION(shuffle){
zval *array;
if (zend_parse_parameters(1 TSRMLS_CC, "a", &a...
_人人人人人人人人人人人人_
> ランダムマージソート <
 ̄Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y ̄
implementation of str_shuffle (php < 4.3.0)
PHP_FUNCTION(str_shuffle)
{
/* Note : by using current php_string_shuffle for ...
implementation of str_shuffle
(php < 4.3.0)
static int php_string_shuffle(const void *a,
const void *b TSRMLS_DC)
{
long r...
_人人人人人人人人人人人人人人人_
> ランダム(?) クイックソート <
 ̄Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y ̄
emulate old shuffle (php)
bench("old_shuffle", function(&$ary){
usort($ary, function($a, $b) {
return (rand() % 2) ? 1 : -...
result
old_shuffle
Array
(
[123] => 22358
[132] => 7627
[213] => 3771
[231] => 3827
[312] => 7487
[321] => 14930
)
old_str...
現在の shuffle は、本当に問題ないのか?
php_rand(C) := rand (php)
random in php
rand
mt_rand
rand vs mt_rand
• rand
– libc の random or lrand48 or rand
– environment dependent
• mt_rand
– Mersenne Twister (MT19937)
–...
re-imprement of shuffle
(environment independent)
function mt_shuffle(&$ary) {
$n = count($ary);
while(--$n) {
$rnd_idx = ...
Conclusion
• 現在の shuffle / str_shuffle は、均等に分配
される
• 異なる環境での再現性が必要なら mt_rand
つかって再実装しよう
• php 4 はオワコン
End Of Slide
Let’s enjoy PHP hack life ;-)
Php radomize
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Php radomize

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第5回 闇php勉強会

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Php radomize

  1. 1. PHP と 乱打舞図 2014/03/15 第5回 闇PHP勉強会 do_aki
  2. 2. @do_aki http://do-aki.net/
  3. 3. title was born from typo らんだまいず 乱打舞図 モテカルロ法っぽくない?
  4. 4. randomize • 無秩序に並び替えること • 規則性がないこと • 偏りがないこと
  5. 5. http://nmi.jp/archives/541 (http://www.lauradhamilton.com/random- lessons-online-poker-exploit)
  6. 6. randomize function in php shuffle str_shuffle
  7. 7. give it try (php 5.5.10) function bench($name, $suffle_func) { $result = []; for ($i=0; $i<60000;++$i) { $a = range(1, 3); $suffle_func($a); $r = implode('', $a); $result[$r]=isset($result[$r])? $result[$r]+1 : 1; } print "{$name}¥n"; ksort($result); print_r($result); }
  8. 8. shuffle / str_shuffle bench("shuffle", "shuffle"); bench("str_shuffle", function(&$ary) { $str = str_shuffle(implode('', $ary)); $ary = str_split($str, 1); });
  9. 9. result of shuffle shuffle Array ( [123] => 9873 [132] => 10104 [213] => 9999 [231] => 9944 [312] => 9998 [321] => 10082 )
  10. 10. result of str_shuffle str_shuffle Array ( [123] => 9956 [132] => 9928 [213] => 10080 [231] => 9969 [312] => 10149 [321] => 9918 )
  11. 11. No Problem (in current version of php)
  12. 12. 過去の shuffle は等分散ではなかった
  13. 13. implementation of shuffle(current version) long n_elems, rnd_idx, n_left; char temp; /* The implementation is stolen from array_data_shuffle */ /* Thus the characteristics of the randomization are the same */ n_elems = len; if (n_elems <= 1) { return; } n_left = n_elems; while (--n_left) { rnd_idx = php_rand(TSRMLS_C); RAND_RANGE(rnd_idx, 0, n_left, PHP_RAND_MAX); if (rnd_idx != n_left) { temp = str[n_left]; str[n_left] = str[rnd_idx]; str[rnd_idx] = temp; } } ext/standard/string.c より抜粋 / shuffle の実装も同じ
  14. 14. implementation of shuffle (php < 4.3.0) PHP_FUNCTION(shuffle){ zval *array; if (zend_parse_parameters(1 TSRMLS_CC, "a", &array) == FAILURE){ RETURN_FALSE; } if (zend_hash_sort(Z_ARRVAL_PP(&array), (sort_func_t)php_mergesort, array_data_shuffle, 1 TSRMLS_CC) == FAILURE) { RETURN_FALSE; } RETURN_TRUE; } } static int array_data_shuffle(const void *a, const void *b TSRMLS_DC) { return (php_rand(TSRMLS_C) % 2) ? 1 : -1; }
  15. 15. _人人人人人人人人人人人人_ > ランダムマージソート <  ̄Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y ̄
  16. 16. implementation of str_shuffle (php < 4.3.0) PHP_FUNCTION(str_shuffle) { /* Note : by using current php_string_shuffle for string */ /* with 6 chars (6! permutations) about 2/3 of them are */ /* computed for 6! calls for the function. So it isn't so */ /* unique. The ratio is the same for other lengths. */ char *str; int i, str_len; i = 0; if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s", &str, &str_len) == FAILURE) { RETURN_FALSE; } zend_qsort((void *)str, str_len, sizeof(char), php_string_shuffle TSRMLS_CC); RETURN_STRINGL(str, str_len, 1); }
  17. 17. implementation of str_shuffle (php < 4.3.0) static int php_string_shuffle(const void *a, const void *b TSRMLS_DC) { long rnd; rnd = php_rand(TSRMLS_C); if (rnd % 3) return 1; else if (rnd % 5) return 0; else return -1; }
  18. 18. _人人人人人人人人人人人人人人人_ > ランダム(?) クイックソート <  ̄Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y^Y ̄
  19. 19. emulate old shuffle (php) bench("old_shuffle", function(&$ary){ usort($ary, function($a, $b) { return (rand() % 2) ? 1 : -1; }); }); bench("old_str_shuffle", function(&$ary){ usort($ary, function($a, $b) { $rnd = rand(); if ($rnd % 3) { return 1; } elseif ($rnd % 5) { return 0; } else { return -1; } }); });
  20. 20. result old_shuffle Array ( [123] => 22358 [132] => 7627 [213] => 3771 [231] => 3827 [312] => 7487 [321] => 14930 ) old_str_shuffle Array ( [123] => 30982 [132] => 4453 [213] => 5994 [231] => 2928 [312] => 8979 [321] => 6664 )
  21. 21. 現在の shuffle は、本当に問題ないのか?
  22. 22. php_rand(C) := rand (php)
  23. 23. random in php rand mt_rand
  24. 24. rand vs mt_rand • rand – libc の random or lrand48 or rand – environment dependent • mt_rand – Mersenne Twister (MT19937) – implementation dependent
  25. 25. re-imprement of shuffle (environment independent) function mt_shuffle(&$ary) { $n = count($ary); while(--$n) { $rnd_idx = mt_rand(0, $n); if ($rnd_idx != $n) { $tmp = $ary[$n]; $ary[$n] = $ary[$rnd_idx]; $ary[$rnd_idx] = $tmp; } } }
  26. 26. Conclusion • 現在の shuffle / str_shuffle は、均等に分配 される • 異なる環境での再現性が必要なら mt_rand つかって再実装しよう • php 4 はオワコン
  27. 27. End Of Slide Let’s enjoy PHP hack life ;-)

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