4.9.1. LAMMPS Class¶
The LAMMPS class is encapsulating an MD simulation state and thus it is
the class that needs to be created when starting a new simulation system
state. The LAMMPS executable essentially creates one instance of this
class and passes the command line flags and tells it to process the
provided input (a file or
stdin). It shuts the class down when
control is returned to it and then exits. When using LAMMPS as a
library from another code it is required to create an instance of this
class, either directly from C++ with
new LAMMPS() or through one
of the library interface functions like
lammps_open() of the
C-library interface, or the
lammps.lammps class constructor
of the Python module, or the
lammps() constructor of the Fortran
In order to avoid clashes of function names, all of the core code in
LAMMPS is placed into the
LAMMPS_NS namespace. Functions or variables
outside of that namespace must be “static”, i.e. visible only to the
scope of the file/object they are defined in. Code in packages or the
libraries in the
lib folder may not adhere to this as some of them
are adapted from legacy code or consist of external libraries with their
own requirements and policies.
LAMMPS simulation instance.
The LAMMPS class manages the components of an MD simulation by creating, deleting, and initializing instances of the classes it is composed of, processing command line flags, and providing access to some global properties. The specifics of setting up and running a simulation are handled by the individual component class instances.
const char *match_style(const char *style, const char *name)¶
Return name of package that a specific style belongs to.
This function checks the given name against all list of styles for all type of styles and if the name and the style match, it returns which package this style belongs to.
style – Type of style (e.g. atom, pair, fix, etc.)
name – Name of style
Name of the package this style is part of
LAMMPS(int, char**, MPI_Comm)¶
Create a LAMMPS simulation instance
The LAMMPS constructor starts up a simulation by allocating all fundamental classes in the necessary order, parses input switches and their arguments, initializes communicators, screen and logfile output FILE pointers.
narg – number of arguments
arg – list of arguments
communicator – MPI communicator used by this LAMMPS instance
Shut down a LAMMPS simulation instance
The LAMMPS destructor shuts down the simulation by deleting top-level class instances, closing screen and log files for the global instance (aka “world”) and files and MPI communicators in sub-partitions (“universes”). Then it deletes the fundamental class instances and copies of data inside the class.
- const char *match_style(const char *style, const char *name)¶
Base class for LAMMPS features.
The Pointers class contains references to many of the pointers and members of the LAMMPS_NS::LAMMPS class. Derived classes thus gain access to the constituent class instances in the LAMMPS composite class and thus to the core functionality of LAMMPS.
This kind of construct is needed, since the LAMMPS constructor should only be run once per LAMMPS instance and thus classes cannot be derived from LAMMPS itself. The Pointers class constructor instead only initializes C++ references to component pointer in the LAMMPS class.