Edit report at https://bugs.php.net/bug.php?id=45184&edit=1
ID: 45184
Updated by: php-bugs@lists.php.net
Reported by: kala at sankya dot com
Summary: algorithm to limit random numbers to a certain range
is flawed
-Status: Feedback
+Status: No Feedback
Type: Bug
Package: Math related
Operating System: Linux
PHP Version: 5.2.6
Assigned To: pajoye
New Comment:
No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Open". Thank you.
Previous Comments:
------------------------------------------------------------------------
[2010-05-21 12:14:13] m...@php.net
Should probably be in feedback state.
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[2008-06-18 16:21:40] paj...@php.net
Would you be interested in improving our code?
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[2008-06-05 11:49:10] kala at sankya dot com
Sorry the line
int val = (i/divisor)*10;
in the example program should be :
int val = (i/divisor)*REQUESTED_RANGE;
for the program to work correctly for any other range other than 10.
------------------------------------------------------------------------
[2008-06-05 11:30:09] kala at sankya dot com
@pajoye : Yes I'm aware of the limitations of rand() (and LCG generators in
general), and have used MT extensively. The problem here isn't with the RNG but
with the algorithm used in converting the raw 31 bit random number to one
within a given range. This algorithm is common to both the rand() and mt_rand()
functions that take min/max arguments (both uses the RANGE_RANDOM macro defined
in the file "ext/standard/php_rand.h") . The only work around is to use the no
argument variant to get a 31 bit number and and do the scaling yourself. (But
obviously the better solution would be to fix the code itself :) )
------------------------------------------------------------------------
[2008-06-05 10:37:10] paj...@php.net
Have you tried to use mt_rand instead?
Rand is known for having "issues".
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the rest of the comments, please view the bug report online at
https://bugs.php.net/bug.php?id=45184
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