ID: 24142
Comment by: webmaster at ragnarokonline dot de
Reported By: infohata at firmos dot net
Status: Bogus
Bug Type: Zend Engine 2 problem
Operating System: Linux
PHP Version: 5.0.0-dev
Assigned To: stas
New Comment:
The test-case hasn't been corrected for PHP 4.3.3-dev
Previous Comments:
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[2003-06-16 14:16:12] [EMAIL PROTECTED]
Should always test myself and not trust others:
# /usr/src/web/php/php5/sapi/cli/php -n t.php
5.04499999999999992894573
5.04999999999999982236432
5.04999999999999982236432
5.05
No bug anywhere.
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[2003-06-16 14:00:55] [EMAIL PROTECTED]
With this script:
<?php
$mul = 1;
$one = 5;
$two = 0.9;
ini_set("precision", 24);
$res = 5 * (1 + (0.9 / 100));
$bar = round($res, 2);
$foo = round(1 * $bar, 2);
echo $res, "\n", $bar, "\n", $foo, "\n";
echo sprintf("%1.2f", $foo);
?>
Result with PHP 4.3.3-dev:
5.04499999999999992894573
5.04999999999999982236432
5.04999999999999982236432
5.05
Result with PHP 4.2.3:
5.04499999999999992894573
5.04000000000000003552714
5.04000000000000003552714
5.04
Nokia 6120 (the $res):
5.045
TI-32:
5.045
With pen and paper:
5.045
Round 5.045 with precision of 2 == 5.05
So I think PHP 4.3.2 actually works as expected
and anything before (and after, PHP 5? :) doesn't.
Reclassified as ZE2 bug.
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[2003-06-16 12:10:33] [EMAIL PROTECTED]
Stas, I was so free to assign this to you :)
------------------------------------------------------------------------
[2003-06-16 12:09:50] [EMAIL PROTECTED]
hmm, actually this changed between PHP 4.2.2, PHP 4.2.3 an PHP 4.3.0:
[EMAIL PROTECTED] derick]$ cat foo.php
<?php
$mul = 1;
$one = 5;
$two = 0.9;
echo sprintf("%1.2f", round($mul * round($one * (1 + ($two / 100)), 2),
2));
?>
[EMAIL PROTECTED] derick]$ php-4.2.2 foo.php
5.04
[EMAIL PROTECTED] derick]$ php-4.2.3 foo.php
5.05zend_hash.c(98) : Bailed out without a bailout address!
[EMAIL PROTECTED] derick]$ php-4.3.0 foo.php
5.05
[EMAIL PROTECTED] derick]$ php-4.3.0dev foo.php
5.05
[EMAIL PROTECTED] derick]$ php-5.0.0dev foo.php
5.04
So something is definitely screwed in the PHP_4_3 branch
Derick
------------------------------------------------------------------------
[2003-06-12 02:45:09] [EMAIL PROTECTED]
This is expected behaviour. When rounding on exact halves we round
down on evens and up on odds. If you want to always force it in one
direction on a .5 (or .05 in your case) add or substract a tiny fuzz
factor. The reason behind rounding half the values down and the other
half up is to avoid the classical banking problem where if you always
rounded down you would be stealing money from your customers, or if you
always rounded up you would end up over time losing money. By
averaging it out through evens and odds you statistically break even.
If you want to learn more, search the web for terms such as "round to
even" or "banker's rounding" and you will find that most languages
actually do it this way.
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The remainder of the comments for this report are too long. To view
the rest of the comments, please view the bug report online at
http://bugs.php.net/24142
--
Edit this bug report at http://bugs.php.net/?id=24142&edit=1
