Half neighbourlist output wrong

[agoscinski]

I don't get symmetric forces for dimers (pbc set to false).
Results were obtained on branch lammps_preparations running file examples/cpp/krr_model.cc with input model examples/h2_model.json" and input structure reference_data/inputs/h2.json`

Output full neighbour list

manager->offsets
2, 
0, 2, 4, 

manager->nb_neigh
2, 
2, 2, 

manager->atom_tag_list
0, 1, 
0, 1, 1, 0, 

manager->neighbours_cluster_index

neighbor list without ghosts
center atom tag 0, cluster index 0
  pair (0, 1): global index 1, pair dist 1, direction vector 1 0 0
center atom tag 1, cluster index 1
  pair (1, 0): global index 3, pair dist 1, direction vector -1  0  0

neighbor list with ghost
center atom tag 0, cluster index 0
  pair (0, 0): global index 0, pair dist 0, direction vector 0 0 0
  pair (0, 1): global index 1, pair dist 1, direction vector 1 0 0
center atom tag 1, cluster index 1
  pair (1, 1): global index 2, pair dist 0, direction vector 0 0 0
  pair (1, 0): global index 3, pair dist 1, direction vector -1  0  0

-0.0314014
ee shape: 1, 1
ff shape: 2, 3
ff 
-1.72423        0        0
 1.72423        0        0

Output half neighbour list

manager->offsets
2, 
0, 2, 3, 

manager->nb_neigh
2, 
2, 1, 

manager->atom_tag_list
0, 1, 
0, 1, 1, 

manager->neighbours_cluster_index

neighbor list without ghosts
center atom tag 0, cluster index 0
  pair (0, 1): global index 1, pair dist 1, direction vector 1 0 0
center atom tag 1, cluster index 1

neighbor list with ghost
center atom tag 0, cluster index 0
  pair (0, 0): global index 0, pair dist 0, direction vector 0 0 0
  pair (0, 1): global index 1, pair dist 1, direction vector 1 0 0
center atom tag 1, cluster index 1
  pair (1, 1): global index 2, pair dist 0, direction vector 0 0 0

-0.0314014
ee shape: 1, 1
ff shape: 2, 3
ff 
-0.862114         0         0
  1.72423         0         0

Not urgent for the lammps integration, since we can use the full one.