Edit report at https://bugs.php.net/bug.php?id=55368&edit=1
ID: 55368
Comment by: good821 at 126 dot com
Reported by: ygautheron at absystech dot fr
Summary: ini_set('precision',16) is affecting a simple math
result
Status: Bogus
Type: Bug
Package: *Math Functions
Operating System: Linux Gentoo (2.6.38-gentoo-r6)
PHP Version: 5.3.6
Block user comment: N
Private report: N
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[2011-08-29 08:08:40] good821 at 126 dot com
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[2011-08-08 09:21:59] cataphr...@php.net
Floating point values have a limited precision. Hence a value might
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly
printing it without any mathematical operations.
If you would like to know more about "floats" and what IEEE
754 is, read this:
http://www.floating-point-gui.de/
Thank you for your interest in PHP.
Expected.
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[2011-08-05 08:47:48] ygautheron at absystech dot fr
Ok, well i assume the only patch is
var_dump(round(1.196-1,3)*100);
I think it's buggy, but maybe there is no C solution to add in the PHP source ?
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[2011-08-05 08:40:09] jeremie dot gw at gmail dot com
I don't think it is a php bug. I have the same result with C code.
Source :
--------
#include "stdio.h"
int main(){
double a;
a=(1.196-1)*100;
printf("Result=%.16f\n",a);
return 0;
}
Result :
--------
19.5999999999999943
Architecture :
--------------
Ubuntu 10.04 x86
Linux 2.6.32-33-generic #71-Ubuntu SMP Wed Jul 20 17:30:40 UTC 2011 i686
GNU/Linux
gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)
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[2011-08-05 08:29:07] ygautheron at absystech dot fr
Just noticed that i we try 0.196*100 it works good too.
The problem seems to come from the substract ?
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