[Developers] [Patches] Make ADMConstraints GF public

Erik Schnetter schnetter at cct.lsu.edu
Tue Sep 19 09:51:17 CDT 2006


On Sep 19, 2006, at 05:29:11, Luca Baiotti wrote:

> Hi,
>
> so, my character-comparison proposal is clearly unviable (...) and
> Jonathan's, for example, is far superior.
>
> However,
>
> Erik Schnetter wrote:
>> In that case, the numbers
>>
>>     0.000000000000123
>>     0.000000000000456
>>
>> would compare different. However, if these are constraint violations,
>> they should be treated as equal.
>
> I don't understand why the above numbers should be considered equal or
> their difference acceptable. Testsuites have, in my view, the aim of
> 1) checking whether a patch made to a code has accidentally changed
> something that the patch was not supposed to change (if the patch is
> supposed to change the testsuite output, then the testsuites should  
> also
> be updated by the author of the patch);
> 2) checking whether running on different machines (or on different
> number of processors) produces different results, in which case the  
> bug
> in the code or the problem with the machine should be addressed.
>
> Following this view, the numbers above should fail the testsuite.

Differences of that order of magnitude are normal and are to be  
expected when changing the number of processors, compilers, compiler  
options, hardware, or whatever.  Compiler optimisers optimise code by  
executing the operations in a different (faster) order, and the  
roundoff error depends on the order.  A relative error of 1.0e-12 or  
so is to be expected.

-erik

-- 
Erik Schnetter <schnetter at cct.lsu.edu>

My email is as private as my paper mail.  I therefore support encrypting
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