11.6. Compute styles

Classes that compute scalar and vector quantities like temperature and the pressure tensor, as well as classes that compute per-atom quantities like kinetic energy and the centro-symmetry parameter are derived from the Compute class. New styles can be created to add new calculations to LAMMPS.

Compute_temp.cpp is a simple example of computing a scalar temperature. Compute_ke_atom.cpp is a simple example of computing per-atom kinetic energy.

Here is a brief description of methods you define in your new derived class. See compute.h for details.

init perform one time setup (required)
init_list neighbor list setup, if needed (optional)
compute_scalar compute a scalar quantity (optional)
compute_vector compute a vector of quantities (optional)
compute_peratom compute one or more quantities per atom (optional)
compute_local compute one or more quantities per processor (optional)
pack_comm pack a buffer with items to communicate (optional)
unpack_comm unpack the buffer (optional)
pack_reverse pack a buffer with items to reverse communicate (optional)
unpack_reverse unpack the buffer (optional)
remove_bias remove velocity bias from one atom (optional)
remove_bias_all remove velocity bias from all atoms in group (optional)
restore_bias restore velocity bias for one atom after remove_bias (optional)
restore_bias_all same as before, but for all atoms in group (optional)
pair_tally_callback callback function for tally-style computes (optional).
memory_usage tally memory usage (optional)

Tally-style computes are a special case, as their computation is done in two stages: the callback function is registered with the pair style and then called from the Pair::ev_tally() function, which is called for each pair after force and energy has been computed for this pair. Then the tallied values are retrieved with the standard compute_scalar or compute_vector or compute_peratom methods. The USER-TALLY package provides examples_compute_tally.html for utilizing this mechanism.