From:
Operating system: Multiple
PHP version: 5.2.13
Package: Math related
Bug Type: Bug
Bug description:should add to zero, but gets 1.1102230246252E-16 instead
Description:
------------
Math error for code that should be returning zero, but instead returns
1.1102230246252E-16 on multiple systems using multiple versions of PHP.
The problem is that when the input value is -3 the output value should be
zero: 0.9 + (-3 * 0.3) = 0.9 - 0.9 = 0. If the calculated value is
non-zero the error does not occur.
I first saw the error on a WinXP (Home SP3, 32bit) system running PHP
5.2.9-1, but it also shows up on a MAC (10.6.2) with PHP 5.3.0 installed.
I'm in the process of upgrading PHP (to 5.2.13) on my Gentoo box to test it
there but haven't had a chance to do so yet.
Test script:
---------------
my_function(-3);
function my_function($input){
$output = 1;
if($input <= 0)
$output = 0.9 + ($input * 0.3);
// the above should give 0.9 - 0.9 = 0
echo "Verifying values: 0.9 - ".($input * 0.3)." is supposed to be
zero?\n";
echo "Input: $input\tOutput: $output\n";
return $output;
}
Expected result:
----------------
should have received zero (0).
Actual result:
--------------
actually received: 1.1102230246252E-16
--
Edit bug report at http://bugs.php.net/bug.php?id=51518&edit=1
--
Try a snapshot (PHP 5.2):
http://bugs.php.net/fix.php?id=51518&r=trysnapshot52
Try a snapshot (PHP 5.3):
http://bugs.php.net/fix.php?id=51518&r=trysnapshot53
Try a snapshot (PHP 6.0):
http://bugs.php.net/fix.php?id=51518&r=trysnapshot60
Fixed in SVN:
http://bugs.php.net/fix.php?id=51518&r=fixed
Fixed in SVN and need be documented:
http://bugs.php.net/fix.php?id=51518&r=needdocs
Fixed in release:
http://bugs.php.net/fix.php?id=51518&r=alreadyfixed
Need backtrace:
http://bugs.php.net/fix.php?id=51518&r=needtrace
Need Reproduce Script:
http://bugs.php.net/fix.php?id=51518&r=needscript
Try newer version:
http://bugs.php.net/fix.php?id=51518&r=oldversion
Not developer issue:
http://bugs.php.net/fix.php?id=51518&r=support
Expected behavior:
http://bugs.php.net/fix.php?id=51518&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=51518&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=51518&r=submittedtwice
register_globals:
http://bugs.php.net/fix.php?id=51518&r=globals
PHP 4 support discontinued: http://bugs.php.net/fix.php?id=51518&r=php4
Daylight Savings: http://bugs.php.net/fix.php?id=51518&r=dst
IIS Stability:
http://bugs.php.net/fix.php?id=51518&r=isapi
Install GNU Sed:
http://bugs.php.net/fix.php?id=51518&r=gnused
Floating point limitations:
http://bugs.php.net/fix.php?id=51518&r=float
No Zend Extensions:
http://bugs.php.net/fix.php?id=51518&r=nozend
MySQL Configuration Error:
http://bugs.php.net/fix.php?id=51518&r=mysqlcfg
