1--TEST-- 2Bug #75170: mt_rand() bias on 64-bit machines 3--CREDITS-- 4Solar Designer in https://externals.io/message/100229 5--FILE-- 6<?php 7 8// PHP pre-7.1.0 modulo bias 9mt_srand(1234567890); 10$total = 10000; 11$max = 0x66666666; 12$halves[0] = $halves[1] = 0; 13for ($i = 0; $i < $total; $i++) { 14 $halves[(mt_rand(0, $max - 1) >> 1) & 1]++; 15} 16printf("%.1f%% vs. %.1f%%\n", 100. * $halves[0] / $total, 100. * $halves[1] / $total); 17 18// PHP 7.1.0 to 7.2.0beta2 modulo bias bug found during work 19// on http://www.openwall.com/php_mt_seed/ 20mt_srand(1234567890); 21$total = 10000; 22$max = 0x66666666; 23$halves[0] = $halves[1] = 0; 24for ($i = 0; $i < $total; $i++) { 25 $halves[mt_rand(0, $max - 1) / ($max / 2)]++; 26} 27printf("%.1f%% vs. %.1f%%\n", 100. * $halves[0] / $total, 100. * $halves[1] / $total); 28 29?> 30--EXPECT-- 3149.5% vs. 50.5% 3250.5% vs. 49.5% 33
