def energy_conservation_tester():
w0 = numpy.pi*2
sho_funcs = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -config[1]*(w0)**2)
]
x0 = 1.0
tfin = 50.0
start = time.time()
path = rk_comp.rk45(sho_funcs, [0, float(x0), 0], tfin, precision=10**-10)
end = time.time()
print(len(path), tfin/len(path))
print('took %.3f seconds' % (end-start))
times = map(lambda point: point[0], path)
potential = map(lambda point: (w0**2/2.)*point[1]**2, path)
kinetic = map(lambda point: point[2]**2/2, path)
total = numpy.array(potential)+numpy.array(kinetic)
# pyplot.plot(times, potential)
# pyplot.plot(times, kinetic)
# pyplot.plot(times, total)
error = abs(total-total[0])/total[0]
pyplot.plot(times, numpy.log10(error))
#-5 got about 4.8 digits, -6 got 5.9, -7 got 6.5, -8 got 7.7
#-9 got 8.3 digits -10 get 9.6 digit after 6 minutes
pyplot.show()
return
def pather_drawing():
target = [(lambda state: 1), (lambda state: state[3]),
(lambda state: state[4]),
(lambda state: -2 * state[1] * state[2]**2 *
(1 - state[1]**2) * numpy.exp(-(state[1]**2 + state[2]**2))),
(lambda state: -2 * state[1]**2 * state[2] *
(1 - state[2]**2) * numpy.exp(-(state[1]**2 + state[2]**2)))]
runs = 4
# b_vals = numpy.linspace(.9, .25, runs)
b_vals = numpy.linspace(.9, .25, runs - 1)
b_vals = numpy.append(b_vals, 2.3)
fig, axes = pyplot.subplots(runs, 3)
axes[0][0].set_xlabel('x')
axes[0][0].set_ylabel('y')
axes[0][1].set_xlabel('x')
axes[0][1].set_ylabel('vx')
axes[0][2].set_xlabel('y')
axes[0][2].set_ylabel('vy')
for b_index in range(len(b_vals)):
b = b_vals[b_index]
path = rk_comp.rk45(target, [0, -5.5, b, .5, 0], 25.0)
x_vals = column(path, 1)
y_vals = column(path, 2)
vx_vals = column(path, 3)
vy_vals = column(path, 4)
axes[b_index][0].scatter([1, 1, -1, -1], [1, -1, 1, -1], facecolor='r')
axes[b_index][0].scatter(x_vals, y_vals)
axes[b_index][1].scatter(x_vals, vx_vals)
axes[b_index][2].scatter(y_vals, vy_vals)
# axes.set_ylim([-2.5, 2.5])
# axes.set_xlim([-2.5, 2.5])
fig.tight_layout()
pyplot.savefig("%d.png" % int(time.time()))
def backwards_test():
w0 = numpy.pi * 2
forward_funcs = [(lambda config: 1), (lambda config: config[2]),
(lambda config: -config[1] * (w0)**2)]
backward_funcs = [(lambda config: +1), (lambda config: -config[2]),
(lambda config: +config[1] * (w0)**2)]
path1 = rk_comp.rk45(forward_funcs, [0, 1., 0], 5.0)
path2 = rk_comp.rk45(backward_funcs, [0, path1[-1][1], path1[-1][2]],
path1[-1][0])
flipped_path2 = time_reverser(path1[-1][0], path2)
ordered_path2 = sorted(flipped_path2, key=(lambda point: point[0]))
print(len(path1), len(ordered_path2))
print(path1[0], ordered_path2[0:3])
#results: reversed path has 4 times as many points in it?! by nature of rk45, path2 does not actually include t=0, does get within 10**-13, though
#decision: rk45 as implemented is messy for this purpose, numerov should be implemented
# rk_comp.plot_paths([path1, flipped_path2], ['forward', 'back'])
return
def beating():
w0 = numpy.pi*2
f0 = w0**2
wd = numpy.pi*2.5
sho_funcs = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -config[1]*(w0)**2)
]
drive_funcs = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -config[1]*(w0)**2+f0*numpy.sin(wd*config[0]))
]
x0 = 1.0
tfin = 50.0
start = time.time()
path0 = rk_comp.rk45(sho_funcs, [0, float(x0), 0], tfin, precision=10**-6)
path1 = rk_comp.rk45(drive_funcs, [0, float(x0), 0], tfin, precision=10**-6)
end = time.time()
print(end-start)
rk_comp.plot_paths([path0, path1])
def sho_tester():
w0 = numpy.pi*2
sho_funcs = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -config[1]*(w0)**2)
]
calculated_periods = []
for x0 in range(1,3):
path = rk_comp.rk45(sho_funcs, [0, float(x0), 0], 20.0, precision=10**-5)
print(len(path))
calculated_periods.append(period_finder(path))
compare_extremas(max_displace(path, count=3), min_veloc(path, count=3))
print(calculated_periods)
return
def non_harmonic_beating():
w0 = numpy.pi*2
f0 = w0**2
wd = numpy.pi*1.2
drive_funcs = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -config[1]**5+3*numpy.sin(wd*config[0])-0.1*config[2])
]
x0 = 1.5
tfin = 150.0
start = time.time()
path1 = rk_comp.rk45(drive_funcs, [0, float(x0), 0], tfin, precision=10**-6)
end = time.time()
print(end-start)
rk_comp.plot_paths([ path1])
def metastable_seperatrix():
a, b = 4.0, 3.0
well_func = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -a*config[1]-b*config[1]**2.0)
]
print(-a/b)
seperatrix = -a/b
# seperatrix = -a/(2.*b)
starts = numpy.linspace(seperatrix*.01, seperatrix, 20)-seperatrix*.000001
periods = []
for x0 in starts:
print(x0)
path = rk_comp.rk45(well_func, [0,x0, 0], 20.0, precision=10**-5)
periods.append(period_finder(path))
pyplot.plot(starts, periods)
pyplot.show()
return
def period_vs_totalE():
'''
amplitudes selected to compare total energy to total energy
'''
energies = 1.25**numpy.arange(-5, 7)
sets_of_periods = []
for power in range(5):
p = 2*power + 1
periods = []
well_funcs = [
(lambda config: 1),
(lambda config: config[2]),
(lambda config: -p*config[1]**p)
]
for energy in energies:
x0 = energy**(1.0/p)
path = rk_comp.rk45(well_funcs, [0, x0, 0], 20.0, precision=10**-5)
periods.append(period_finder(path))
pyplot.plot(energies, periods)
pyplot.show()
return
def deflection(scattering_func, y0=.5, v0=.5):
path = rk_comp.rk45(scattering_func, [0, -5.5, y0, v0, 0], 15.0)
theta = numpy.arctan2(path[-1][4], path[-1][3])
return theta