Re: [ESPResSo-users] Force scaling wrong

[Joost de Graaf]

Dear Floh & Marcello,

I'm not sure if it's that good an idea to make the forces read-only. I can assure you, they are definitely not that way in the current code and for good reasons. If you want to reinitialize the LB fluid, you need the reuse_forces command, to account for the fact that the LB use of forces is half a time step off of that in the main integration loop. That's why you want to keep them settable. (as I wrote this Henri's message came in).

Kind Regards, Joost

On 28 February 2015 at 12:23, Florian Weik <address@hidden> wrote:

Hi,

Marcello is right, these forces are never used. For technical reasons it is not that easy to make them read-only because a lot of the test cases rely on the fact that forces can be read via the blockfile mechanism which is in turn just an interface to the tcl part command. So unless somebody is volunteering for the busywork to change dozens of test cases, that situation is staying the way it is. I'm pretty sure the documentation reflects the fact that these forces are not used.

Cheers,

Florian

On Sat, Feb 28, 2015 at 8:36 AM, Marcello Sega <address@hidden> wrote:

Hi,

please correct me if I'm wrong: I think that forces are always
overwritten by the integrator, so that setting them by hand does not
have any effect at all.

If this is right, then allowing to set forces could be just misleading
(as the program would behave in a way unexpected by the user).
Wouldn't it be better to make them read-only?

Regards,

Marcello

On Fri, Feb 27, 2015 at 3:56 PM, Henri Menke <address@hidden> wrote:
> Dear all,
>
> in the current master of ESPResSo the forces are scaled by the masses
> and the time step in the output, i.e. part 0 print f, but are not scaled
> by the mass in the input, i.e. part 0 f.  This leads to wrong forces
> when setting them by hand with a mass not equal to 1.
>
> This bug is fixed in the pull-request
>
>   https://github.com/espressomd/espresso/pull/213
>
> Kind regards,
> Henri
>

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Institut für Computergestützte Biologische Chemie
University of Vienna
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Florian Weik, Dipl.-Phys.,
Institut für Computerphysik, Allmandring 3, D-70569 Stuttgart
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