#43171 [Opn]: nonrandom rand() results in lower bits

ID: 43171 User updated by: bdew at druzya dot org Reported By: bdew at druzya dot org Status: Open Bug Type: Math related Operating System: windows xp sp2 PHP Version: 5.2.4 New Comment: Err, sory... "If i use rand(x,y) the bug does happen only when max_rand+2>y>max_rand+2" should have read "If i use rand(x,y) the bug does happen only when max_rand+2>y>max_rand-2" Previous Comments: ------------------------------------------------------------------------ [2007-11-01 13:30:23] bdew at druzya dot org Description: ------------ Under windows xp cli version, rand() seems to return cycling values in lower bits. If i use rand(x,y) the bug does happen only when max_rand+2>y>max_rand+2 mt_rand() is unaffected Tested same code under linux cli and the bug doesn't happen. possibly related to http://bugs.php.net/bug.php?id=43108 Reproduce code: --------------- $a=rand() & 0xff; for ($k=0;$k<10;$k++) { $i=0; do { $i++; $b=rand() & 0xff; } while ($a!=$b); echo("cycle: $i\n"); }; Expected result: ---------------- 10 lines with "cycle: x", x being different every line Actual result: -------------- cycle: 256 cycle: 256 cycle: 256 cycle: 256 cycle: 256 cycle: 256 cycle: 256 cycle: 256 cycle: 256 cycle: 256 every time ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=43171&edit=1