|
sponsored links |
|
|
sponsored links
|
|
1
29th December 19:13
External User
Posts: 1
|
#27052 : rand() returns easily predictable numbers
From: webmaster at armondc dot com
Operating system: Windows 2000 Professional PHP version: 4.3.4 PHP Bug Type: Unknown/Other Function Bug description: rand() returns easily predictable numbers Description: ------------ I'm not sure if this is a very major problem, or even a bug, but here goes: It seems rand() on Windows is very predictable. I've tried it on 2 Windows Systems, and they were both predictable. It showed a breif unpredictable segment, then followed by the same string of characters over and over, and finally a few more unpredictable characters. I tried this on a FreeBSD 5.2 System, and it was unpreditable enough. Seems to be a windows-only problem. I also noticed bug#11108 - It seems similar, but the submitter was using his own seeds, and I am using without. Reproduce code: --------------- <?php // This will reproduce the problem // on windows for($x = 0; $x < 500; $x++) { echo chr((rand()%32)+65); } // This is a quick-fix, but // goes agaist the do***entation's // 'no need for srand()' for($x = 0; $x < 500; $x++) { srand(hexdec(substr(md5(microtime()), 0, 8))); echo chr((rand()%32)+65); } ?> Expected result: ---------------- Something a bit random like: HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSU`UHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_`D`F \X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[`XL\SSHQXOYQU_JDMM`ZEUEOQOYMHJPYDTRRU_URHYJGXRQYDY ADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\`XFQJNOWQKAJBFONFXNDZFF IMYRL`ROH^]IM_MINJI\MJJAVG`]_B_EAV`C\O_\DHCHLX_NIO`U^KMJF\`K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[`\AG[PV^XLPRYVAS]ZPH`^WAXYAZYGK_M_QK`F]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD Actual result: -------------- An easily spotted pattern: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ -- Edit bug report at http://bugs.php.net/?id=27052&edit=1 -- Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=27052&r=trysnapshot4 Try a CVS snapshot (php5): http://bugs.php.net/fix.php?id=27052&r=trysnapshot5 Fixed in CVS: http://bugs.php.net/fix.php?id=27052&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=27052&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=27052&r=needtrace Need Reproduce Script: http://bugs.php.net/fix.php?id=27052&r=needscript Try newer version: http://bugs.php.net/fix.php?id=27052&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=27052&r=support Expected behavior: http://bugs.php.net/fix.php?id=27052&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=27052&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=27052&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=27052&r=globals PHP 3 support discontinued: http://bugs.php.net/fix.php?id=27052&r=php3 Daylight Savings: http://bugs.php.net/fix.php?id=27052&r=dst IIS Stability: http://bugs.php.net/fix.php?id=27052&r=isapi Install GNU Sed: http://bugs.php.net/fix.php?id=27052&r=gnused Floating point limitations: http://bugs.php.net/fix.php?id=27052&r=float |
|
|
|
2
29th December 19:13
External User
Posts: 1
|
#27052 : rand() returns easily predictable numbers
ID: 27052
User updated by: webmaster at armondc dot com Reported By: webmaster at armondc dot com Status: Open Bug Type: Unknown/Other Function Operating System: Windows 2000 Professional PHP Version: 4.3.4 New Comment: On the "actual result" its not as easily spotted without wrapping. This should give a better picture: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ Previous Comments: ------------------------------------------------------------------------ [2004-01-26 15:53:26] webmaster at armondc dot com Description: ------------ I'm not sure if this is a very major problem, or even a bug, but here goes: It seems rand() on Windows is very predictable. I've tried it on 2 Windows Systems, and they were both predictable. It showed a breif unpredictable segment, then followed by the same string of characters over and over, and finally a few more unpredictable characters. I tried this on a FreeBSD 5.2 System, and it was unpreditable enough. Seems to be a windows-only problem. I also noticed bug#11108 - It seems similar, but the submitter was using his own seeds, and I am using without. Reproduce code: --------------- <?php // This will reproduce the problem // on windows for($x = 0; $x < 500; $x++) { echo chr((rand()%32)+65); } // This is a quick-fix, but // goes agaist the do***entation's // 'no need for srand()' for($x = 0; $x < 500; $x++) { srand(hexdec(substr(md5(microtime()), 0, 8))); echo chr((rand()%32)+65); } ?> Expected result: ---------------- Something a bit random like: HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSU`UHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_`D`F \X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[`XL\SSHQXOYQU_JDMM`ZEUEOQOYMHJPYDTRRU_URHYJGXRQYDY ADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\`XFQJNOWQKAJBFONFXNDZFF IMYRL`ROH^]IM_MINJI\MJJAVG`]_B_EAV`C\O_\DHCHLX_NIO`U^KMJF\`K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[`\AG[PV^XLPRYVAS]ZPH`^WAXYAZYGK_M_QK`F]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD Actual result: -------------- An easily spotted pattern: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=27052&edit=1 |
|
|
|
3
29th December 19:13
External User
Posts: 1
|
#27052 : rand() returns easily predictable numbers
ID: 27052
Updated by: sniper@php.net Reported By: webmaster at armondc dot com -Status: Open +Status: Feedback -Bug Type: Unknown/Other Function +Bug Type: Math related Operating System: Windows 2000 Professional PHP Version: 4.3.4 New Comment: Please try using this CVS snapshot: http://snaps.php.net/php4-STABLE-latest.tar.gz For Windows: http://snaps.php.net/win32/php4-win32-STABLE-latest.zip Some rand() related bugs have already been fixed.. Previous Comments: ------------------------------------------------------------------------ [2004-01-26 15:56:22] webmaster at armondc dot com On the "actual result" its not as easily spotted without wrapping. This should give a better picture: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ [2004-01-26 15:53:26] webmaster at armondc dot com Description: ------------ I'm not sure if this is a very major problem, or even a bug, but here goes: It seems rand() on Windows is very predictable. I've tried it on 2 Windows Systems, and they were both predictable. It showed a breif unpredictable segment, then followed by the same string of characters over and over, and finally a few more unpredictable characters. I tried this on a FreeBSD 5.2 System, and it was unpreditable enough. Seems to be a windows-only problem. I also noticed bug#11108 - It seems similar, but the submitter was using his own seeds, and I am using without. Reproduce code: --------------- <?php // This will reproduce the problem // on windows for($x = 0; $x < 500; $x++) { echo chr((rand()%32)+65); } // This is a quick-fix, but // goes agaist the do***entation's // 'no need for srand()' for($x = 0; $x < 500; $x++) { srand(hexdec(substr(md5(microtime()), 0, 8))); echo chr((rand()%32)+65); } ?> Expected result: ---------------- Something a bit random like: HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSU`UHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_`D`F \X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[`XL\SSHQXOYQU_JDMM`ZEUEOQOYMHJPYDTRRU_URHYJGXRQYDY ADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\`XFQJNOWQKAJBFONFXNDZFF IMYRL`ROH^]IM_MINJI\MJJAVG`]_B_EAV`C\O_\DHCHLX_NIO`U^KMJF\`K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[`\AG[PV^XLPRYVAS]ZPH`^WAXYAZYGK_M_QK`F]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD Actual result: -------------- An easily spotted pattern: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=27052&edit=1 |
|
|
|
4
29th December 19:14
External User
Posts: 1
|
#27052 : rand() returns easily predictable numbers
ID: 27052
User updated by: webmaster at armondc dot com Reported By: webmaster at armondc dot com -Status: Feedback +Status: Open Bug Type: Math related Operating System: Windows 2000 Professional -PHP Version: 4.3.4 +PHP Version: 4.3.5RC2-dev New Comment: I tried it on 4.3.5RC2-dev, and it's still relativly the same. The pattern is slightly different, but is still as predictable as before. Previous Comments: ------------------------------------------------------------------------ [2004-01-26 19:04:34] sniper@php.net Please try using this CVS snapshot: http://snaps.php.net/php4-STABLE-latest.tar.gz For Windows: http://snaps.php.net/win32/php4-win32-STABLE-latest.zip Some rand() related bugs have already been fixed.. ------------------------------------------------------------------------ [2004-01-26 15:56:22] webmaster at armondc dot com On the "actual result" its not as easily spotted without wrapping. This should give a better picture: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ [2004-01-26 15:53:26] webmaster at armondc dot com Description: ------------ I'm not sure if this is a very major problem, or even a bug, but here goes: It seems rand() on Windows is very predictable. I've tried it on 2 Windows Systems, and they were both predictable. It showed a breif unpredictable segment, then followed by the same string of characters over and over, and finally a few more unpredictable characters. I tried this on a FreeBSD 5.2 System, and it was unpreditable enough. Seems to be a windows-only problem. I also noticed bug#11108 - It seems similar, but the submitter was using his own seeds, and I am using without. Reproduce code: --------------- <?php // This will reproduce the problem // on windows for($x = 0; $x < 500; $x++) { echo chr((rand()%32)+65); } // This is a quick-fix, but // goes agaist the do***entation's // 'no need for srand()' for($x = 0; $x < 500; $x++) { srand(hexdec(substr(md5(microtime()), 0, 8))); echo chr((rand()%32)+65); } ?> Expected result: ---------------- Something a bit random like: HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSU`UHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_`D`F \X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[`XL\SSHQXOYQU_JDMM`ZEUEOQOYMHJPYDTRRU_URHYJGXRQYDY ADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\`XFQJNOWQKAJBFONFXNDZFF IMYRL`ROH^]IM_MINJI\MJJAVG`]_B_EAV`C\O_\DHCHLX_NIO`U^KMJF\`K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[`\AG[PV^XLPRYVAS]ZPH`^WAXYAZYGK_M_QK`F]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD Actual result: -------------- An easily spotted pattern: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=27052&edit=1 |
|
|
|
5
29th December 19:14
External User
Posts: 1
|
#27052 : rand() returns easily predictable numbers
ID: 27052
Updated by: sniper@php.net Reported By: webmaster at armondc dot com -Status: Open +Status: Bogus Bug Type: Math related Operating System: Windows 2000 Professional PHP Version: 4.3.5RC2-dev New Comment: RTFM: Note: On some platforms (such as Windows) RAND_MAX is only 32768. If you require a range larger than 32768, consider using mt_rand() instead. Previous Comments: ------------------------------------------------------------------------ [2004-01-26 20:03:17] webmaster at armondc dot com I tried it on 4.3.5RC2-dev, and it's still relativly the same. The pattern is slightly different, but is still as predictable as before. ------------------------------------------------------------------------ [2004-01-26 19:04:34] sniper@php.net Please try using this CVS snapshot: http://snaps.php.net/php4-STABLE-latest.tar.gz For Windows: http://snaps.php.net/win32/php4-win32-STABLE-latest.zip Some rand() related bugs have already been fixed.. ------------------------------------------------------------------------ [2004-01-26 15:56:22] webmaster at armondc dot com On the "actual result" its not as easily spotted without wrapping. This should give a better picture: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ [2004-01-26 15:53:26] webmaster at armondc dot com Description: ------------ I'm not sure if this is a very major problem, or even a bug, but here goes: It seems rand() on Windows is very predictable. I've tried it on 2 Windows Systems, and they were both predictable. It showed a breif unpredictable segment, then followed by the same string of characters over and over, and finally a few more unpredictable characters. I tried this on a FreeBSD 5.2 System, and it was unpreditable enough. Seems to be a windows-only problem. I also noticed bug#11108 - It seems similar, but the submitter was using his own seeds, and I am using without. Reproduce code: --------------- <?php // This will reproduce the problem // on windows for($x = 0; $x < 500; $x++) { echo chr((rand()%32)+65); } // This is a quick-fix, but // goes agaist the do***entation's // 'no need for srand()' for($x = 0; $x < 500; $x++) { srand(hexdec(substr(md5(microtime()), 0, 8))); echo chr((rand()%32)+65); } ?> Expected result: ---------------- Something a bit random like: HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSU`UHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_`D`F \X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[`XL\SSHQXOYQU_JDMM`ZEUEOQOYMHJPYDTRRU_URHYJGXRQYDY ADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\`XFQJNOWQKAJBFONFXNDZFF IMYRL`ROH^]IM_MINJI\MJJAVG`]_B_EAV`C\O_\DHCHLX_NIO`U^KMJF\`K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[`\AG[PV^XLPRYVAS]ZPH`^WAXYAZYGK_M_QK`F]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD Actual result: -------------- An easily spotted pattern: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=27052&edit=1 |
|
|
|
6
29th December 19:15
External User
Posts: 1
|
#27052 : rand() returns easily predictable numbers
ID: 27052
User updated by: webmaster at armondc dot com Reported By: webmaster at armondc dot com Status: Bogus Bug Type: Math related Operating System: Windows 2000 Professional PHP Version: 4.3.5RC2-dev New Comment: I do not see what RAND_MAX has to do with it, and excuse me if I'm wrong here- for($x = 0; $x < 15000; $x++) { echo chr((rand(0,32768)%32)+65); } This code should replicate the problem on a unix-like platform, however from my tests it doesn't. Just trying to help  Previous Comments: ------------------------------------------------------------------------ [2004-01-26 20:06:10] sniper@php.net RTFM: Note: On some platforms (such as Windows) RAND_MAX is only 32768. If you require a range larger than 32768, consider using mt_rand() instead. ------------------------------------------------------------------------ [2004-01-26 20:03:17] webmaster at armondc dot com I tried it on 4.3.5RC2-dev, and it's still relativly the same. The pattern is slightly different, but is still as predictable as before. ------------------------------------------------------------------------ [2004-01-26 19:04:34] sniper@php.net Please try using this CVS snapshot: http://snaps.php.net/php4-STABLE-latest.tar.gz For Windows: http://snaps.php.net/win32/php4-win32-STABLE-latest.zip Some rand() related bugs have already been fixed.. ------------------------------------------------------------------------ [2004-01-26 15:56:22] webmaster at armondc dot com On the "actual result" its not as easily spotted without wrapping. This should give a better picture: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F [LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ [2004-01-26 15:53:26] webmaster at armondc dot com Description: ------------ I'm not sure if this is a very major problem, or even a bug, but here goes: It seems rand() on Windows is very predictable. I've tried it on 2 Windows Systems, and they were both predictable. It showed a breif unpredictable segment, then followed by the same string of characters over and over, and finally a few more unpredictable characters. I tried this on a FreeBSD 5.2 System, and it was unpreditable enough. Seems to be a windows-only problem. I also noticed bug#11108 - It seems similar, but the submitter was using his own seeds, and I am using without. Reproduce code: --------------- <?php // This will reproduce the problem // on windows for($x = 0; $x < 500; $x++) { echo chr((rand()%32)+65); } // This is a quick-fix, but // goes agaist the do***entation's // 'no need for srand()' for($x = 0; $x < 500; $x++) { srand(hexdec(substr(md5(microtime()), 0, 8))); echo chr((rand()%32)+65); } ?> Expected result: ---------------- Something a bit random like: HEOSITFS[ZYH_EVIVVXSLCWRHHC_]_L^PIBTC\TXPBWQLCM^VZSU`UHOG[\VF[KCDGFZM^Q\IG^KAIYPIYBSBIMGHXIBMPHLY\OAZMYAZPJ_`D`F \X\QXR[GP]DQLRHMYIOERBMEKBDJMJPN]J\\KPES^EGRKKO^S[`XL\SSHQXOYQU_JDMM`ZEUEOQOYMHJPYDTRRU_URHYJGXRQYDY ADD]OBVUGC^GGSXPRJJAOAKRAYYN^Q\`XFQJNOWQKAJBFONFXNDZFF IMYRL`ROH^]IM_MINJI\MJJAVG`]_B_EAV`C\O_\DHCHLX_NIO`U^KMJF\`K]VZDOZ_FAWCZC_IQK^[NTPZCC]XEFZ[`\AG[PV^XLPRYVAS]ZPH`^WAXYAZYGK_M_QK`F]PRMP^BBPTRV^KV_VDOLFIM]WQNHVF^DYWGGSGLJ_ZMODG[Z_AAXBYD^FS\MITLZESC`DXLH]NWNIVWZZMVMSXFQMG[O[W[YSPVMTQLHD Actual result: -------------- An easily spotted pattern: ]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\YRWXENCTQJOP]F[LIBGHU^SDAZ_`MVK\ ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=27052&edit=1 |
|
|
|
Linear Mode
