[gmx-developers] Inconsistent force calculating result between generic kernel and interaction-specific kernel?

[francesco oteri]

In my case the excuse was that the system administrator never updated the
compiler.
So I after a couple of days I installed the new compiler.
In any case, I noticed that the problem disappeared using the "Debug"
version so  I guess
it is something related either to the optimized kernel or the optimization
strategy used by the compiler.


Francesco


2013/6/8 Mark Abraham <mark.j.abraham at gmail.com>

>
>
>
> On Sat, Jun 8, 2013 at 12:59 PM, francesco oteri <
> francesco.oteri at gmail.com> wrote:
>
>> H Mark,
>> I had a similar problem recently and, eventually, I figured out the cause
>> was the compiler version.
>> I was using gcc4.1 and my problem got solved using a more recent version.
>> Actually, this issue
>> in the website is clearly stated. So, which compiler are you using?
>> Could you report an example of inconsistency?
>>
>
> That warning has been there many years, but AFAIK nobody ever identified
> the real problem (if it exists). Nevertheless, there is no excuse for using
> both GROMACS and such an old compiler! :-)
>
> Mark
>
>
>> Francesco
>>
>>
>> 2013/6/8 Mark Abraham <mark.j.abraham at gmail.com>
>>
>>>
>>>
>>>
>>> On Sat, Jun 8, 2013 at 1:44 AM, Mark Tianwu Zang <zangtw at gmail.com>wrote:
>>>
>>>> Dear all,
>>>> I have inserted only a few lines after update() in md.c to monitor how
>>>> forces change after every step. My codes are very simple, just like:
>>>>
>>>> for i=0 to md->nalloc
>>>>  fprintf f[i][0], f[i][1], f[i][2]
>>>>
>>>
>>> That seems like the hard way to do it, with nstfout available in the
>>> .mdp file.
>>>
>>> However, I found the results of my output become quite different after
>>>> exporting GMX_NB_GENERIC=1, which means the forces calculated by generic
>>>> kernel and interaction-specific kernel are not the same. I am a little
>>>> confused now.. It this phenomena quite normal or I ignored something
>>>> important?
>>>>
>>>
>>> AFAIK the generic kernel should serve as a reference for the
>>> interaction-specific kernels. If not, there might a problem to fix. Hard to
>>> say without context.
>>>
>>> Mark
>>>
>>> Thanks a lot!
>>>> -Mark
>>>>
>>>>
>>>>
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>>
>>
>>
>> --
>> Cordiali saluti, Dr.Oteri Francesco
>>
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-- 
Cordiali saluti, Dr.Oteri Francesco
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