[gmx-developers] real in C++

[Berk Hess]

On 2/25/13 20:06 , David van der Spoel wrote:
> On 2013-02-25 16:39, Berk Hess wrote:
>> Yes, for this we would want to introduce multiple different reals.
>>
> But what is wrong with having double and real, as we do now?
There is nothing wrong per se. But we might want to be able to have all 
of mdrun
in double precision, except for the non-bonded calculations.

Cheers,

Berk
>
>
>> Cheers,
>>
>> Berk
>>
>> On 02/25/2013 04:37 PM, Szilárd Páll wrote:
>>> One thing to note is that we would like to have an additional mixed
>>> precision scheme, hopefully in 5.0. The idea is that part of the code,
>>> like force calculations, would run in single precision with fixed
>>> precision accumulators/reduction and double for whatever it makes
>>> sense/is useful. Using real everywhere could make achieving this quite
>>> difficult, right?
>>>
>>> -- 
>>> Szilárd
>>>
>>>
>>> On Mon, Feb 25, 2013 at 3:50 PM, Mark Abraham
>>> <mark.j.abraham at gmail.com <mailto:mark.j.abraham at gmail.com>> wrote:
>>>
>>>     I'm not aware of a need to change the way we implement this.
>>>
>>>     Berk and I have mooted the desirability of switching our naming
>>>     scheme to "double-" vs "mixed-precision" on the grounds that
>>>     aspects of the virial computation have been in double precision
>>>     for a long time. We may as well avoid people leaping to the
>>>     conclusion that "single-precision" GROMACS must be dodgy because
>>>     you need double precision for some aspects of the algorithm.
>>>
>>>     Mark
>>>
>>>     On Sun, Feb 24, 2013 at 10:09 PM, David van der Spoel
>>>     <spoel at xray.bmc.uu.se <mailto:spoel at xray.bmc.uu.se>> wrote:
>>>
>>>         Hi,
>>>
>>>         did we decide on how to treat real variables in C++?
>>>         There is nothing stopping us from keeping the same
>>>
>>>         #ifdef GMX_DOUBLE
>>>         typedef double real;
>>>         #else
>>>         typedef float real;
>>>         #endif
>>>
>>>         that we have use for decades. Or is there reason to change it?
>>>
>>>         Cheers,
>>>         --
>>>         David van der Spoel, Ph.D., Professor of Biology
>>>         Dept. of Cell & Molec. Biol., Uppsala University.
>>>         Box 596, 75124 Uppsala, Sweden. Phone: +46184714205
>>>         <tel:%2B46184714205>.
>>>         spoel at xray.bmc.uu.se <mailto:spoel at xray.bmc.uu.se>
>>>         http://folding.bmc.uu.se
>>>         --
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>>
>>
>>
>
>