[ESPResSo-devel] BondList access

[Tristan Bereau]

Hello,

I am encountering something unexpected from ESPResSo when trying to
get bondlists (i.e. information about the bonded partners of a given
particle) whithin the 'add_non_bonded_pair_force' function in the
forces.h file.
This function takes a given pair of non-bonded particles (let's call
them 1 and 2) and calculate all the forces on them. At the beginning
of this function I output some variable related to the bond partners
of both particles 1 and 2, namely the commands :
p1->bl.n
p2->bl.n
(I understand that this variable bl.n is the sum of all bonded
interactions and bonded partners.)

Here's a short part of the output :
...
# of partners for particle 1 : 2; # of partners for particle 2 : 2
# of partners for particle 1 : 2; # of partners for particle 2 : 2
# of partners for particle 1 : 2; # of partners for particle 2 : 5
# of partners for particle 1 : 0; # of partners for particle 2 : 1685073459
# of partners for particle 1 : 0; # of partners for particle 2 : 0
# of partners for particle 1 : 0; # of partners for particle 2 : 0
...
As you can imagine, the 4th line is fishy as I have only 6 particles
in my simulation with only bond length and bond angle potentials !
I realized that this problem occurs only for particle 2 (there's
always access to particle 1's bondlist), and particle 2 is always very
well defined as far as its identity and position is concerned. What I
don't understand is the way its bondlist cannot be accessed only
occasionally.

I'm working with the latest CVS version of ESPResSo, and tested this
problem with different simulation scripts.

Any help would be much appreciated.

Best,

Tristan