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- --TEST--
- Bug #75170: mt_rand() bias on 64-bit machines
- --CREDITS--
- Solar Designer in https://externals.io/message/100229
- --FILE--
- <?php
- // PHP pre-7.1.0 modulo bias
- mt_srand(1234567890);
- $total = 10000;
- $max = 0x66666666;
- $halves[0] = $halves[1] = 0;
- for ($i = 0; $i < $total; $i++) {
- $halves[(mt_rand(0, $max - 1) >> 1) & 1]++;
- }
- printf("%.1f%% vs. %.1f%%\n", 100. * $halves[0] / $total, 100. * $halves[1] / $total);
- // PHP 7.1.0 to 7.2.0beta2 modulo bias bug found during work
- // on http://www.openwall.com/php_mt_seed/
- mt_srand(1234567890);
- $total = 10000;
- $max = 0x66666666;
- $halves[0] = $halves[1] = 0;
- for ($i = 0; $i < $total; $i++) {
- $halves[(int) (mt_rand(0, $max - 1) / ($max / 2))]++;
- }
- printf("%.1f%% vs. %.1f%%\n", 100. * $halves[0] / $total, 100. * $halves[1] / $total);
- ?>
- --EXPECT--
- 49.5% vs. 50.5%
- 50.5% vs. 49.5%
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