Edit report at http://bugs.php.net/bug.php?id=51396&edit=1
ID: 51396
Comment by: codeslinger at compsalot dot com
Reported by: codeslinger at compsalot dot com
Summary: Math is Unreliable
Status: Feedback
Type: Bug
Package: Math related
Operating System: any
PHP Version: Irrelevant
New Comment:
as far as the low incidence of occurrence and the millions of users not
seeing it.
I've said all along that it is hard to reproduce. But when dealing with
financial transactions, that is not good enough, it only takes one
mistake to have a huge problem on your hands.
Out of all of those millions of users, I'd venture to say that the very
overwhelming majority are using php for string processing not number
crunching. And in many cases where it does show up such as positioning
something on a web page, it would be easy to shrug off. So there is no
way to know how often this happens in the wild, based on user feedback.
Previous Comments:
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[2010-03-26 21:02:47] codeslinger at compsalot dot com
The billing program was failing on multiple computers at multiple
locations, it failed on XP and Windows 2000 with various cpus. Those
were customer sites! I reproduced the problem on a vmware setup with
windows 2000.
This snowflake program is failing on Ubuntu Hardy 8.0.4 with all of the
updates. This is the stock php that comes with Ubuntu. This is a
Pentium M 32bit Laptop. I've never experienced a memory error on this
computer and the fact of it's consistency would argue against this being
some kind of hardware issue.
Here is what I get when I run the simplefail in the default config.
php -v
PHP 5.2.4-2ubuntu5.10 with Suhosin-Patch 0.9.6.2 (cli) (built: Jan 6
2010 22:01:14)
Copyright (c) 1997-2007 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies
with Xdebug v2.0.3, Copyright (c) 2002-2007, by Derick Rethans
with Zend Debugger v5.2.15, Copyright (c) 1999-2008, by Zend
Technologies
==========
php simplefail.php
Selected onepair.txt, Found 1 items
(string)(double) -0.1 === -0.1 which of course is correct
But when we convert the value in an array it fails
Conversion Error: PHP Math idx = 0 || '-0.1' !== '-0.0:'
=====
THANK YOU I REALLY APPRECIATE THE HELP
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[2010-03-26 17:25:40] [email protected]
Well, it is the next character after '9', and the character string is
built up in zend_dtoa() by adding a value L (presumably intended to be
in the range 0..9) to '0'. If L somehow ends up being 10, you'd get a
colon.
With the values that are apparently causing problems (the problematic
value in onepair.txt is 0.09999999999999999167...), it does kind of look
like a rounding issue to me, although I've no idea why it's not being
triggered by more than two or three users in that case.
------------------------------------------------------------------------
[2010-03-26 17:18:22] [email protected]
Bad memory perhaps? But why consistently a ':' ?
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[2010-03-26 16:57:15] [email protected]
JFTR, I was also unable to reproduce the failure case from any of the
data files on both 32-bit and 64-bit Linux builds and a 32-bit Windows
build. I've got a couple of boxen crunching away generating random
doubles and converting them to strings in what seems to be the sort of
range that causes problems (one 32-bit Linux, one 64-bit Linux): nothing
yet after a couple of billion iterations.
In short, I don't have a clue what it could be either, but I'll keep the
random double generation going a while longer just in case it hits
paydirt.
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[2010-03-26 16:39:33] [email protected]
Rasmus, he is not the only person. There are two other reports about it.
However he is the first one to experience it on non windows platform.
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