ID: 49947
User updated by: haochen at pristineprinting dot com
Reported By: haochen at pristineprinting dot com
Status: Bogus
Bug Type: Math related
Operating System: CentOS 5.3
PHP Version: 5.2.11
New Comment:
Thanks for your quick response.
You are right. I tested in Java and ASP, they lost more precise than
PHP.
Do you think it is 32-bit system limition or current-generation
computer limition?
If my server is AIX, the result will be correct or not?
Anyway, thanks for your answer again. :-)
Previous Comments:
------------------------------------------------------------------------
[2009-10-21 18:09:25] johannes@php.net
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to
report
a bug at http://bugs.php.net/how-to-report.php
pow(2,100)+2 will be converted to a float, and floats aren't precise.
------------------------------------------------------------------------
[2009-10-21 17:29:36] haochen at pristineprinting dot com
Description:
------------
It looks like overflow when I do plus 1. But when I do tims 2, it looks
correct. Strange! I guess times and division move left or right for
binery number(...1011101...). Plus and minus functions maybe have bugs?
I don't know my code is wrong or it is a bug.
Server is Centos 5.3+PHP 5.2.11+Apache = Web Server
I just put this code into public_html
And client is WinXP+SP3+IE7. IE open the php. Wrong result.
Thanks a lot.
Reproduce code:
---------------
<?php
$x=2;
$p=100;
$y=pow($x,$p);
$a=number_format($y);
$b=$y+2;
$c=$y*2;
$r=number_format($a);
$rr=number_format($b);
echo "pow($x,$p) = $a <br><br>";
echo "pow($x,$p)+2 = $r <br><br>";
echo "pow($x,$p)*2 = $rr <br><br>";
?>
Expected result:
----------------
pow(2,100) = 1,267,650,600,228,229,401,496,703,205,376
pow(2,100)+2 = 1,267,650,600,228,229,401,496,703,205,378
pow(2,100)*2 = 2,535,301,200,456,458,802,993,406,410,752
Actual result:
--------------
pow(2,100) = 1,267,650,600,228,229,401,496,703,205,376
pow(2,100)+2 = 1,267,650,600,228,229,401,496,703,205,376
pow(2,100)*2 = 2,535,301,200,456,458,802,993,406,410,752
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=49947&edit=1