# 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.