[ESPResSo] Addendum: Bug in Lennard-Jones interaction in ESPResSo versions 2.1.1u up to 2.1.2d

[Torsten Stuehn]

Dear all,

here are some details, that will help you to find out if you were affected by 
the bug:

* if you had only one short range non bonded lennard-jones interaction e.g.:

     inter $type_1 $type_2 lennard-jones $eps $sig $rcut $shift $offset 
$cap_radius $min_radius
     , where $type_1==0 and $type_2==0 (important !)

 you were _not_ affected by the bug.

 As soon as you had additional short range non bonded interactions ($type_1 > 0 || 
$type_2 > 0)
         e.g. "inter 0 1 <whatever> ... "
 you were affected by the bug (or at least it was purely random, if you were 
affected or not,
 because the variable IA_parameters->LJ_min was not copied in copy_ia_params 
and thus was uninitialized).

 Bonded interactions e.g. "inter 0 fene ..." or long range interactions e.g. "inter coulomb ..." 
 or weather you ran ESPResSo in parallel or on one CPU only had no influence on the bug at all.

* and again: the bug was present _only_ in the "bleeding egde" CVS versions 
2.1.1u to 2.1.2d

* because somebody asked: yes, the ESPResSo testsuite detected the bug 
(testcase mass.tcl did fail)
 but somehow it could escape our attention until yesterday.


Greetings,
Torsten.

Torsten Stuehn wrote:
> Dear all,
>
> due to a bug, which appeared only in the CVS versions 2.1.1u (2009-02-09)
> up to 2.1.2d (2009-03-09) some of the lennard-jones pair-interactions 
> were not
> calculated correctly. All simulations that involved lennard-jones 
> interactions
> (which is most likely all simulations !) and were done with these 
> versions of
> ESPResSo are most likely wrong.
>
> The bug is fixed in version 2.1.2e (2009-03-09)
>
> PLEASE double check your simulations,  if you were using the above 
> mentioned ESPResSo versions !!!
>
> Greetings,
> Torsten.