Frequently Asked Questions

How do I run a NEML2 input file?

NEML2 is designed as a library, not a program: The core library itself cannot be used as a standalone program to parse and evaluate a material model defined in an input file. However, we acknowledge this common need and therefore provide two convenient options for users to effectively use NEML2 as a standalone program:

1. The NEML2 Runner: As documented in build customization, the NEML2_RUNNER CMake option can be turned on to create a simple runner for parsing, diagnosing, running and profiling NEML2 material models. Once the runner is built, an executable will be placed inside the runner directory under the build directory. Invoking the executable without any additional argument or with the -h or --help argument will print out the usage message:

   driver: 1 argument(s) expected. 0 provided.
   Usage: runner [--help] [--version] [--diagnose] [--time] input driver additional_args
    
   Positional arguments:
     input            path to the input file
     driver           name of the driver in the input file
     additional_args  additional command-line arguments to pass to the input file parser [nargs: 0 or more]
    
   Optional arguments:
     -h, --help       shows help message and exits
     -v, --version    prints version information and exits
     -d, --diagnose   run diagnostics on common problems and exit (without further execution)
     -t, --time       output the elapsed wall time during model evaluation

2. The NEML2 Pyton package: As mentioned in the installation guide, NEML2 also provides an experimental Python package which provides bindings for the primitive tensors and parsers for deserializing and running material models. Once the NEML2 Python package is successfully installed, one can follow the user guide for NEML2 Python package to evaluate material models with given inputs.

In addition to the above options, one can always write a simple C++ program and link against NEML2. Boilerplate for the C++ program can be found in the user guide, and CMake integration is documented in the installation guide.