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To: internals <internals@lists.php.net>, "Levi Morrison" <levim@php.net>
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Date: Mon, 04 Feb 2013 22:16:48 +0100
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Subject: Re: [PHP-DEV] PHP 5.4.11 tests: floating point diff
From: glopes@nebm.ist.utl.pt ("Gustavo Lopes")

On Mon, 04 Feb 2013 21:50:23 +0100, Levi Morrison <levim@php.net> wrote:

> I have been compiling PHP under various compilers trying to figure out
> what flags I need for each compiler to pass all tests excluding
> XFAILs. With Intel 13.0.1 I'm down to two failing tests:
>
> =====================================================================
> FAILED TEST SUMMARY
> ---------------------------------------------------------------------
> Test fmod() - basic function test fmod()
> [ext/standard/tests/math/fmod_basic.phpt]
> Test fmod function : 64bit long tests
> [ext/standard/tests/math/fmod_basiclong_64bit.phpt]
> =====================================================================
>
> The only differences are between -0 and 0 (exact diffs at end of  
> message).
>
> My understanding of floating point calculations is that -0 and 0 are
> equivalent, so I can safely ignore the failures. I wanted to first
> check to make sure that is actually true.

No, they are not the same thing for several purposes. For instance, they  
have different serializations. See also:

$ php
<?php $nz = fmod(-2,2); var_dump(atan2(0., $nz), atan2($nz, $nz));
float(3.1415926535898)
float(-3.1415926535898)

So I think you should investigate the cause of the problem (different  
results), rather than ignoring the differences. Possibly the difference  
lies in the Intel math library; in that case, you can either separate the  
tests in two or just ignore the test when compiling with the Intel  
compiler.

> Assuming that the above is correct, I wanted to patch the phpt files
> for the tests to pass. However, I'm not very familiar with that
> format.  How would you suggest altering the tests to make this pass?
>

Check these:

http://qa.php.net/write-test.php
http://qa.php.net/phpt_details.php

You can also inspect the file run-tests.php if you have any doubt.

-- 
Gustavo Lopes