ChaNGa - An adaptable N-body and gas dynamics code.
                  (Charm N-body GrAvity solver)

For documentation, see the web site:
https://github.com/N-BodyShop/changa/wiki/ChaNGa

For more help, subscribe to the list changa-users@u.washington.edu.

Please cite the following papers when publishing results using ChaNGa:

P. Jetley, F. Gioachin, C. Mendes, L. V. Kale, and T. R. Quinn. Massively
parallel cosmological simulations with ChaNGa. In Proceedings of IEEE
International Parallel and Distributed Processing Symposium 2008, 2008.

P. Jetley, L. Wesolowski, F. Gioachin, L. V. Kale, and T. R. Quinn. Scaling
hierarchical n-body simulations on gpu clusters. In Proceedings of the 2010
ACM/IEEE International Conference for High Performance Computing, Networking,
Storage and Analysis, SC ’10, Washington, DC, USA, 2010. IEEE Computer Society. 

Menon, H., Wesolowski, L., Zheng, G., Jetley, P., Kale, L., Quinn, T.,
Governato, F., 2015. Adaptive Techniques for Clustered N-Body Cosmological
Simulations, Computational Astrophysics and Cosmology, 2, 1.

To compile ChaNGa first compile Charm++ or get a precompiled version.  When
building Charm++, there is a special target "ChaNGa" which will build all the
necessary libraries.  Then to compile ChaNGa itself, run:

./configure
make (or gmake)

The executable ChaNGa will be created together with the submit script charmrun
(for most machines).  Configure takes the usual options and also the
"--enable-cooling" option to specify cooling for gas simulations.

To run the code:

./charmrun +p <procs> ChaNGa <param.file> [ additional options ]

This will work on many machines, and can either be run directly or be
submitted through the local scheduler.  However, on some machines the
application will need to be submitted manually.

More information is available in the online wiki:
https://github.com/N-BodyShop/changa/wiki

Several test simulations are included in subdirectories:

A small globular cluster simulation is included in teststep.  This
simulation can give a quick sanity check that the gravity code is
operating correctly.

A small cosmological simulation is included in testcosmo.

A small shock tube (gas only) simulation is included in testshock.

A small gas collapse simulation is included in testcollapse.

For simple performance benchmarking, arbitrary size simulations can be created
using the tools in testdata.

An example simulation that generates movie frames is included in movie.  See
the director.README in that directory for movie-making options.

ACKNOWLEDGMENTS
================

The development of ChaNGa was supported by a National Science
Foundation ITR grant PHY-0205413 to the University of Washington, and
NSF ITR grant NSF-0205611 to the University of Illinois.  Contributors
to the program include Graeme Lufkin, Tom Quinn, Rok Roskar, Greg Stinson,
Ben Keller, Isaac Backus, Filippo Gioachin, Sayantan Chakravorty, Amit Sharma,
Pritish Jetley, Lukasz Wesolowski, Harshitha Menon, Gengbin Zheng,
Phil Miller, Yanhua Sun, Abhishek Gupta, Aditya Devarakonda, Viraj Paropkari,
Edgar Solomonik, Celso Mendes, Joachim Stadel, and James Wadsley.