openmm/examples/cpp-examples

OpenMM C++, C, and Fortran API Examples

These simple "hello world" examples were developed by Christopher Bruns and Michael Sherman. They demonstrate use of the C++, C, and Fortran APIs for OpenMM.

Example Details

Consult the OpenMM user guide for more information on these examples, as well as use of the C and Fortran API wrappers.

HelloArgon (C++, C, Fortran 95)

This is the simplest example we could come up with that does anything interesting. It is three argon atoms interacting in a vacuum via van der Waals forces. It is primarily so you can check that you are able to compile, link, and run correctly with OpenMM. You will also get a many-frame PDB file generated which you can view as an animation in VMD or most other molecular viewers.

HelloSodiumChloride (C++, C, Fortran 95)

This example shows how we recommend using OpenMM so that you can call it from an existing molecular dynamics code with minimal disruption. The example contains Coulomb and van der Waals interactions and implicit solvation in a constant temperature simulation.

HelloEthane (C++ only)

This example shows how to convey bond information to OpenMM. It is organized similarly to HelloSodiumChloride.

HelloWaterBox (C++ only)

This example shows use of explicit solvent in a periodic box. It is organized like the previous two.

Building the examples

This directory includes a Makefile suitable for building the examples under Mac or Linux and possibly Cygwin, using the GCC compiler suite. There is also an NMakefile for use with Microsoft's nmake program. For Fortran, the Makefile expects gfortran to be in the path while NMakefile expects ifort (Intel Fortran). In the VisualStudio subdirectory, there are Visual Studio "solutions" for building HelloArgon in C++, C, and Fortran. You will have to make your own for the other examples or just substitute a different source file for HelloArgon.

You must already have the OpenMM binaries installed to build the examples from source. See the user guide for more information. You may need to slightly edit the Makefile or NMakefile to make it run on your system, depending where you installed OpenMM and the particular requirements of your compiler versions for mixed Fortran/C++ programming.

Type make (or make default) to get just one C++ example built (HelloArgon). Make sure it runs. To compile all example programs type make all. That includes Fortran examples though so you will see failures unless you have gfortran installed (Linux and Mac) or ifort installed (Windows). However, the C++ and C examples should compile with just g++ or cl. To build just one example, type make HelloArgonInC or whatever.

Before you run the executables, remember to add the OpenMM dynamic library directory to your library path. The simplest way to do this is to type the following commands:

• For linux (for the bash shell, assuming installation was done in the default location /usr/local/openmm):

  $ export LD_LIBRARY_PATH=/usr/local/openmm/lib
  

• For Mac (for the bash shell, assuming installation was done in the default location /usr/local/openmm):

  $ export DYLD_LIBRARY_PATH=/usr/local/openmm/lib
  

• For Windows (command tool, assuming installation was done in the default location C:\Program Files\OpenMM):

  C:\> set path=%path%;C:\Program Files\OpenMM\lib