there are various algorithms to reduce the complexity via physically motivated approximations, see http://www.cs.cmu.edu/~scandal/alg/nbody.html http://www.cs.c

there are various algorithms to reduce the complexity via physically motivated approximations, see http://www.cs.cmu.edu/~scandal/alg/nbody.html http://www.cs.cmu.edu/~scandal/alg/nbody.html for an older but accessible introduction