Possible bug in round function

[Wescotte]

PHP 5.0.5 running on Win2k Server

$rate = 0.015;
$value = 15;

echo $rate * $value;
echo "<BR>";
echo round($rate * $value , 2);

output:

0.225
0.22

Shouldn't this be?
0.225
0.23

[Wescotte]

Re: Possible bug in round function

Little update

if I added echo "<BR>" echo round(.225, 2) the output is .23

[Andy Hassall]

Re: Possible bug in round function

On 13 Feb 2006 12:29:18 -0800, "Wescotte" <wescotte@earth link.net> wrote:
[color=blue]
>PHP 5.0.5 running on Win2k Server
>
>$rate = 0.015;
>$value = 15;
>
>echo $rate * $value;
>echo "<BR>";
>echo round($rate * $value , 2);
>
>output:
>
>0.225
>0.22
>
>Shouldn't this be?
>0.225
>0.23[/color]

On 5.1.2 it does output 0.23.

Perhaps see http://bugs.php.net/bug.php?id=24142

--
Andy Hassall :: andy@andyh.co.u k :: http://www.andyh.co.uk
http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool

[Janwillem Borleffs]

Re: Possible bug in round function

Andy Hassall wrote:[color=blue]
> On 5.1.2 it does output 0.23.
>[/color]

Not on my WinXP installation, which produces 0.22

One of the related bug reports (http://bugs.php.net/bug.php?id=35986)
mentions that this isn't a bug, but due to the limited precision of floats.
Perhaps it's processor related...


JW

[Andy Hassall]

Re: Possible bug in round function

On Mon, 13 Feb 2006 22:24:45 +0100, "Janwillem Borleffs" <jw@jwscripts.c om>
wrote:
[color=blue]
>Andy Hassall wrote:[color=green]
>> On 5.1.2 it does output 0.23.[/color]
>
>Not on my WinXP installation, which produces 0.22
>
>One of the related bug reports (http://bugs.php.net/bug.php?id=35986)
>mentions that this isn't a bug, but due to the limited precision of floats.
>Perhaps it's processor related...[/color]

Hum, 0.23 on Linux, 0.22 on Windows 2000. Both are Intel chips. Looks like
there's Windows-specific code in ext/standard/round.c :

#ifndef PHP_ROUND_FUZZ
# ifndef PHP_WIN32
# define PHP_ROUND_FUZZ 0.50000000001
# else
# define PHP_ROUND_FUZZ 0.5
# endif
#endif

#define PHP_ROUND_WITH_ FUZZ(val, places) { \
double tmp_val=val, f = pow(10.0, (double) places); \
tmp_val *= f; \
if (tmp_val >= 0.0) { \
tmp_val = floor(tmp_val + PHP_ROUND_FUZZ) ; \
} else { \
tmp_val = ceil(tmp_val - PHP_ROUND_FUZZ) ; \
} \
tmp_val /= f; \
val = !zend_isnan(tmp _val) ? tmp_val : val; \
} \


Shame there's no comments explaining what this is there for.

--
Andy Hassall :: andy@andyh.co.u k :: http://www.andyh.co.uk
http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool