[Phys-l] higher-order symplectic integrator

[John Denker <jsd@av8n.com>]

Hi --

For those of you who are interested in numerical methods:

There is a higher-order symplectic integrator written by Ernst Hairer et al.
   http://www.unige.ch/~hairer/software.html

I translated it from Fortran to C++.  I cleaned it up a little bit, and
implemented a rudimentary command-line interface for setting some of the
parameters.  You can find the C++ code at:
  http://www.av8n.com/computer/geometric-numerical-integration/

It can integrate one orbit of the Kepler problem in 15 milliseconds on
a several-years-old laptop, returning to the starting position and
velocity with an accuracy of one part in 10^15 or so ... which is not
too shabby.  It can also handle many other tasks, and can easily be
extended.

For more details, see
   http://www.av8n.com/computer/geometric-numerical-integration/README