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1.5. LAMMPS portability and compatibility

The primary form of distributing LAMMPS is through highly portable source code. But also several ways of obtaining LAMMPS as precompiled packages or through automated build mechanisms exist. Most of LAMMPS is written in C++, some support tools are written in Fortran or Python or MATLAB.

1.5.1. Programming language standards

Most of the C++ code currently requires a compiler compatible with the C++11 standard, the KOKKOS package currently requires C++17. Most of the Python code is written to be compatible with Python 3.5 or later or Python 2.7. Some Python scripts require Python 3 and a few others still need to be ported from Python 2 to Python 3.

1.5.2. Build systems

LAMMPS can be compiled from source code using a (traditional) build system based on shell scripts, a few shell utilities (grep, sed, cat, tr) and the GNU make program. This requires running within a Bourne shell (/bin/sh). Alternatively, a build system with different back ends can be created using CMake. CMake must be at least version 3.16.

1.5.3. Operating systems

The primary development platform for LAMMPS is Linux. Thus, the chances for LAMMPS to compile without problems are the best on Linux machines. Also, compilation and correct execution on macOS and Windows (using Microsoft Visual C++) is checked automatically for the largest part of the source code. Some (optional) features are not compatible with all operating systems, either through limitations of the corresponding LAMMPS source code or through incompatibilities of source code or build system of required external libraries or packages.

Executables for Windows may be created natively using either Cygwin or Visual Studio or with a Linux to Windows MinGW cross-compiler.

Additionally, FreeBSD and Solaris have been tested successfully to run LAMMPS and produce results consistent with those on Linux.

1.5.4. Compilers

The most commonly used compilers are the GNU compilers, but also Clang and the Intel compilers have been successfully used on Linux, macOS, and Windows. Also, the Nvidia HPC SDK (formerly PGI compilers) will compile LAMMPS (tested on Linux).

1.5.5. CPU architectures

The primary CPU architecture for running LAMMPS is 64-bit x86, but also 32-bit x86, and 64-bit ARM and PowerPC (64-bit, Little Endian) are regularly tested.

1.5.6. Portability compliance

Only a subset of the LAMMPS source code is fully compliant to all of the above mentioned standards. This is rather typical for projects like LAMMPS that largely depend on contributions from the user community. Not all contributors are trained as programmers and not all of them have access to multiple platforms for testing. As part of the continuous integration process, however, all contributions are automatically tested to compile, link, and pass some runtime tests on a selection of Linux flavors, macOS, and Windows, and on Linux with different compilers. Thus portability issues are often found before a pull request is merged. Other platforms may be checked occasionally or when portability bugs are reported.