tutorial example code: CDG_gd.pyΒΆ

[source code]

from amuse.lab import *

def main(Ncl, mcl, rcl, W0, t_end, n_steps):
    converter = nbody_system.nbody_to_si(mcl, rcl)
    bodies = new_king_model(Ncl, W0, convert_nbody=converter)

    gravity = Hermite(converter)
    channel_from_gravity_to_framework = gravity.particles.new_channel_to(bodies)

    write_set_to_file(bodies.savepoint(0.0 | t_end.unit), "nbody.hdf5", "hdf5", append_to_file=False)

    Etot_init = gravity.kinetic_energy + gravity.potential_energy

    time = zero
    dt = t_end/float(n_steps)
    while time < t_end:
        Etot_prev = Etot_init
        time += dt

        write_set_to_file(bodies.savepoint(time), "nbody.hdf5", "hdf5")

        Ekin = gravity.kinetic_energy
        Epot = gravity.potential_energy
        Etot = Ekin + Epot

        print "T=", time, "M=", bodies.mass.sum(), "E= ", Etot, "Q= ", Ekin/Epot,
        print "dE=", (Etot_init-Etot)/Etot, "ddE=", (Etot_prev-Etot)/Etot


def new_option_parser():
    from amuse.units.optparse import OptionParser
    result = OptionParser()
    result.add_option("-N", dest="Ncl", type="int",
           default = 100, help="number of stars [%default]")
    result.add_option("-t", unit=units.Myr, dest="t_end",
           type="float", default = 1|units.Myr,
           help="end time of the simulation [%default]")
    result.add_option("-n", dest="n_steps", type="float",
           default = 100, help="number of output steps [%default]")
    result.add_option("-m", unit=units.parsec, dest="mcl",
           type="float", default = 10**7|units.MSun,
           help="cluster mass [%default]")
    result.add_option("-r", unit=units.parsec, dest="rcl",
           type="float", default = 10|units.parsec,
           help="cluster half-mass radius [%default]")
    result.add_option("-W", dest="W0", type="float", default = 7.0,
           help="King model structure parameter [%default]")
    return result

if __name__ in ('__main__'):
    set_printing_strategy("custom", preferred_units =
        [units.MSun, units.RSun, units.yr], precision = 4,
        prefix = "", separator = " [", suffix = "]")
    o, arguments  = new_option_parser().parse_args()

Keywords: python, amuse, astrophysics, matplotlib, pylab, example, codex (see how-to-search-examples)