filter¶
Particle filters describe criteria to select subsets of particles in the
system for use by various operations throughout HOOMD. To maintain high
performance, filters are not re-evaluated on every use. Instead, each unique
particular filter (defined by the class name and hash) is mapped to a group,
an internally maintained list of the selected particles. Subsequent uses of the
same particle filter specification (in the same hoomd.Simulation) will resolve
to the same group and the originally selected particles, even if the state
of the system has changed.
Groups are not completely static. HOOMD-blue automatically re-evaluates the
filter specifications and updates the group membership whenever the number of
particles in the simulation changes. Use hoomd.update.FilterUpdater to
manually trigger updates to group membership.
For molecular dynamics simulations, each group maintains a count of the number
of degrees of freedom given to the group by integration methods. This count is
used by hoomd.md.compute.ThermodynamicQuantities and the integration methods
themselves to compute the kinetic temperature. See
hoomd.State.update_group_dof for details on when HOOMD-blue updates this
count.
- hoomd.filter.filter_like¶
An object that acts like a particle filter.
Either a subclass of
ParticleFilterorCustomFilter.alias of
ParticleFilter|CustomFilter
Classes