ID: 34599 Updated by: [EMAIL PROTECTED] Reported By: osolo at wndtabs dot com -Status: Open +Status: Bogus Bug Type: *Math Functions Operating System: Linux PHP Version: 4.4.0 New Comment:
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://docs.sun.com/source/806-3568/ncg_goldberg.html Thank you for your interest in PHP. Previous Comments: ------------------------------------------------------------------------ [2005-09-22 16:04:20] osolo at wndtabs dot com Description: ------------ The round() function will return inconsistent results when PHP is compiled under certain Linux distro/CPU/compiler combinations. For example, if when compiling PHP on Gentoo 1.12.0_pre6/cc 3.4.4/Pentium 4, we get: round(0.245,2) => 0.24 Instead of the expected 0.25. I've traced the problem to the PHP_ROUND_WITH_FUZZ macro in ext/standard/math.c. This macro starts out as: #define PHP_ROUND_WITH_FUZZ(val, places) { \ double tmp_val=val, f = pow(10.0, (double) places); \ ... Changing the first line to: volatile double tmp_val=val; double f = pow(10.0, (double) places); \ I suspect the problem is that the optimizer is keeping tmp_val in a floating point register that has a difference precision than a C double. Declaring it volatile keeps it in the variable and makes things more consisntant. ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=34599&edit=1
