def run_ph4(infile=None,
outfile=None,
number_of_stars=100,
number_of_binaries=0,
end_time=10 | nbody_system.time,
delta_t=1 | nbody_system.time,
n_workers=1,
use_gpu=1,
gpu_worker=1,
salpeter=0,
accuracy_parameter=0.1,
softening_length=0.0 | nbody_system.length,
manage_encounters=1,
random_seed=1234,
debug_level=1):
if random_seed <= 0:
numpy.random.seed()
random_seed = numpy.random.randint(1, pow(2, 31) - 1)
numpy.random.seed(random_seed)
print("random seed =", random_seed)
if infile != None: print("input file =", infile)
print("end_time =", end_time)
print("delta_t =", delta_t)
print("n_workers =", n_workers)
print("use_gpu =", use_gpu)
print("manage_encounters =", manage_encounters)
print("\ninitializing the gravity module")
sys.stdout.flush()
init_smalln()
# Note that there are actually three GPU options:
#
# 1. use the GPU code and allow GPU use (default)
# 2. use the GPU code but disable GPU use (-g)
# 3. use the non-GPU code (-G)
if gpu_worker == 1:
try:
gravity = grav(number_of_workers=n_workers,
redirection="none",
mode="gpu")
except Exception as ex:
gravity = grav(number_of_workers=n_workers, redirection="none")
else:
gravity = grav(number_of_workers=n_workers, redirection="none")
gravity.initialize_code()
gravity.parameters.set_defaults()
#-----------------------------------------------------------------
if infile == None:
print("making a Plummer model")
stars = new_plummer_model(number_of_stars)
id = numpy.arange(number_of_stars)
stars.id = id + 1
print("setting particle masses and radii")
if salpeter == 0:
print('equal masses')
total_mass = 1.0 | nbody_system.mass
scaled_mass = total_mass / number_of_stars
else:
print('salpeter mass function')
scaled_mass = new_salpeter_mass_distribution_nbody(number_of_stars)
stars.mass = scaled_mass
print("centering stars")
stars.move_to_center()
print("scaling stars to virial equilibrium")
stars.scale_to_standard(
smoothing_length_squared=gravity.parameters.epsilon_squared)
else:
# Read the input data. Units are dynamical (sorry).
# Format: id mass pos[3] vel[3]
print("reading file", infile)
id = []
mass = []
pos = []
vel = []
f = open(infile, 'r')
count = 0
for line in f:
if len(line) > 0:
count += 1
cols = line.split()
if count == 1: snap = int(cols[0])
elif count == 2: number_of_stars = int(cols[0])
elif count == 3: time = float(cols[0]) | nbody_system.time
else:
if len(cols) >= 8:
id.append(int(cols[0]))
mass.append(float(cols[1]))
pos.append(
(float(cols[2]), float(cols[3]), float(cols[4])))
vel.append(
(float(cols[5]), float(cols[6]), float(cols[7])))
f.close()
stars = datamodel.Particles(number_of_stars)
stars.id = id
stars.mass = mass | nbody_system.mass
stars.position = pos | nbody_system.length
stars.velocity = vel | nbody_system.speed
#stars.radius = 0. | nbody_system.length
total_mass = stars.mass.sum()
ke = pa.kinetic_energy(stars)
kT = ke / (1.5 * number_of_stars)
if number_of_binaries > 0:
# Turn selected stars into binary components.
# Only tested for equal-mass case.
kep = Kepler(redirection="none")
kep.initialize_code()
added_mass = 0.0 | nbody_system.mass
# Work with energies rather than semimajor axes.
Emin = 10 * kT
Emax = 20 * kT
ecc = 0.1
nbin = 0
companion_base_id = 100 * (number_of_stars // 10)
for i in range(0, number_of_stars,
number_of_stars // number_of_binaries):
# Star i is CM, becomes component, add other star at end.
nbin += 1
mass = stars[i].mass
new_mass = numpy.random.uniform() * mass # uniform q
mbin = mass + new_mass
fac = new_mass / mbin
E = Emin + numpy.random.uniform() * (Emax - Emin)
a = 0.5 * nbody_system.G * mass * new_mass / E
kep.initialize_from_elements(mbin, a, ecc)
# Binaries should be approaching in order to be picked up
# by multiples.
kep.advance_to_apastron()
kep.advance_to_radius(a)
dr = quantities.AdaptingVectorQuantity()
dr.extend(kep.get_separation_vector())
dv = quantities.AdaptingVectorQuantity()
dv.extend(kep.get_velocity_vector())
newstar = datamodel.Particles(1)
newstar.mass = new_mass
newstar.position = stars[i].position + (1 - fac) * dr
newstar.velocity = stars[i].velocity + (1 - fac) * dv
stars[i].position = stars[i].position - fac * dr
stars[i].velocity = stars[i].velocity - fac * dv
newstar.id = companion_base_id + stars[i].id
stars.add_particles(newstar)
added_mass += new_mass
if nbin >= number_of_binaries: break
kep.stop()
print('created', nbin, 'binaries')
sys.stdout.flush()
stars.mass = stars.mass * total_mass / (total_mass + added_mass)
number_of_stars += nbin
# Set dynamical radii (assuming virial equilibrium and standard
# units). Note that this choice should be refined, and updated
# as the system evolves. Probably the choice of radius should be
# made entirely in the multiples module. TODO. In these units,
# M = 1 and <v^2> = 0.5, so the mean 90-degree turnaround impact
# parameter is
#
# b_90 = G (m_1+m_2) / vrel^2
# = 2 <m> / 2<v^2>
# = 2 / N for equal masses
#
# Taking r_i = m_i / 2<v^2> = m_i in virial equilibrium means
# that, approximately, "contact" means a 90-degree deflection (r_1
# + r_2 = b_90). A more conservative choice with r_i less than
# this value will isolate encounters better, but also place more
# load on the large-N dynamical module.
stars.radius = stars.mass.number | nbody_system.length
time = 0.0 | nbody_system.time
# print "IDs:", stars.id.number
print("recentering stars")
stars.move_to_center()
sys.stdout.flush()
#-----------------------------------------------------------------
if softening_length < 0.0 | nbody_system.length:
# Use ~interparticle spacing. Assuming standard units here. TODO
eps2 = 0.25*(float(number_of_stars))**(-0.666667) \
| nbody_system.length**2
else:
eps2 = softening_length * softening_length
print('softening length =', eps2.sqrt())
gravity.parameters.timestep_parameter = accuracy_parameter
gravity.parameters.epsilon_squared = eps2
gravity.parameters.use_gpu = use_gpu
# gravity.parameters.manage_encounters = manage_encounters
print('')
print("adding particles")
# print stars
sys.stdout.flush()
gravity.particles.add_particles(stars)
gravity.commit_particles()
print('')
print("number_of_stars =", number_of_stars)
sys.stdout.flush()
# Channel to copy values from the code to the set in memory.
channel = gravity.particles.new_channel_to(stars)
stopping_condition = gravity.stopping_conditions.collision_detection
stopping_condition.enable()
# Debugging: prevent the multiples code from being called.
if 0:
stopping_condition.disable()
print('stopping condition disabled')
sys.stdout.flush()
# -----------------------------------------------------------------
# Create the coupled code and integrate the system to the desired
# time, managing interactions internally.
kep = init_kepler(stars[0], stars[1])
multiples_code = multiples.Multiples(gravity, new_smalln, kep)
multiples_code.neighbor_perturbation_limit = 0.1
#multiples_code.neighbor_distance_factor = 2.0
multiples_code.neighbor_veto = True
multiples_code.global_debug = debug_level
print('')
print('multiples_code.initial_scale_factor =', \
multiples_code.initial_scale_factor)
print('multiples_code.neighbor_perturbation_limit =', \
multiples_code.neighbor_perturbation_limit)
print('multiples_code.neighbor_veto =', \
multiples_code.neighbor_veto)
print('multiples_code.final_scale_factor =', \
multiples_code.final_scale_factor)
print('multiples_code.initial_scatter_factor =', \
multiples_code.initial_scatter_factor)
print('multiples_code.final_scatter_factor =', \
multiples_code.final_scatter_factor)
print('multiples_code.retain_binary_apocenter =', \
multiples_code.retain_binary_apocenter)
print('multiples_code.wide_perturbation_limit =', \
multiples_code.wide_perturbation_limit)
# Find initial binaries.
gravity.parameters.zero_step_mode = 1
print('\nidentifying initial binaries')
multiples_code.evolve_model(time)
gravity.parameters.zero_step_mode = 0
pre = "%%% "
E0, cpu0 = print_log(pre, time, multiples_code)
print("evolving to time =", end_time, \
"in steps of", delta_t)
while time < end_time:
time += delta_t
multiples_code.evolve_model(time)
# Copy values from the module to the set in memory.
channel.copy()
# Copy the index (ID) as used in the module to the id field in
# memory. The index is not copied by default, as different
# codes may have different indices for the same particle and
# we don't want to overwrite silently.
channel.copy_attribute("index_in_code", "id")
print_log(pre, time, multiples_code, E0, cpu0)
sys.stdout.flush()
#-----------------------------------------------------------------
if not outfile == None:
# Write data to a file.
f = open(outfile, 'w')
#--------------------------------------------------
# Need to save top-level stellar data and parameters.
# Need to save multiple data and parameters.
f.write('%.15g\n' % (time.number))
for s in multiples_code.stars:
write_star(s, f)
#--------------------------------------------------
f.close()
print('wrote file', outfile)
print('')
gravity.stop()
