ID: 24142 Updated by: [EMAIL PROTECTED] -Summary: round() does 5.045 to 5.04 instrad of 5.05 Reported By: infohata at firmos dot net -Status: Open +Status: Assigned Bug Type: Scripting Engine problem Operating System: Linux PHP Version: 4.3.2 -Assigned To: +Assigned To: stas New Comment:
Stas, I was so free to assign this to you :) Previous Comments: ------------------------------------------------------------------------ [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. ------------------------------------------------------------------------ [2003-06-12 02:28:26] infohata at firmos dot net Description: ------------ I am using a webhosting service of bbdsoft (www.firmos.net) so I don't know exact OS and configuration of PHP.INI, but this bug is independent of any config or OS, it's about round() function - it has a big bug rounding floats!! All the details and what's have to be is written below in the source code and it's comments:) Well, I saw other reports, and I think YOU SHOULD FIX THIS IN ANY CASE AND AS FAST AS POSSIBLE!!! Reproduce code: --------------- // at the start of the return code these variables has values: $skerd_svoris = 1; $rows_kriu_kain00[0] = 5; $rows_kriu_kkoef[0] = 0.9; // return code: return sprintf("%1.2f", round($skerd_svoris*round($rows_kriu_kain00[0]*(1+($rows_kriu_kkoef[0]/100)), 2), 2)); // if the code is changed to: // return sprintf("%1.2f", round($skerd_svoris*round($rows_kriu_kain00[0]*(1+($rows_kriu_kkoef[0]/100))+0.000001, 2), 2)); // all goes OK; so the problem is that if the number is 5.045, rounded it will be 5.04, but if it is 5.045001 - rounded it will be 5.05. I think You understood what I want to say:) Expected result: ---------------- 5.05 Actual result: -------------- 5.04 ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=24142&edit=1