def test_demag_two_spin_xx():
mesh = CuboidMesh(nx=2, ny=1, nz=1)
sim = Sim(mesh)
demag = Demag()
sim.add(demag)
sim.set_m((1, 0, 0))
field = demag.compute_field()
print(field)
assert (field[0] == 2e-7)
assert (field[3] == 2e-7)
def test_demag_two_spin_xx():
mesh = CuboidMesh(nx=2, ny=1, nz=1)
sim = Sim(mesh)
demag = Demag()
sim.add(demag)
sim.set_m((1, 0, 0))
field = demag.compute_field()
print field
assert(field[0] == 2e-7)
assert(field[3] == 2e-7)
def test_demag_fft_exact_oommf():
mesh = CuboidMesh(nx=5, ny=3, nz=2, unit_length=1e-9)
sim = Sim(mesh)
demag = Demag()
sim.add(demag)
def init_m(pos):
x = pos[0]
if x <= 2:
return (1, 0, 0)
elif x >= 4:
return (0, 0, 1)
else:
return (0, 1, 0)
sim.set_m(init_m)
fft = demag.compute_field()
exact = demag.compute_exact()
np.testing.assert_allclose(fft, exact, rtol=1e-10)
def test_demag_fft_exact():
mesh = CuboidMesh(nx=5, ny=3, nz=4)
sim = Sim(mesh)
demag = Demag()
sim.add(demag)
def init_m(pos):
x = pos[0]
if x <= 2:
return (1, 0, 0)
elif x >= 4:
return (0, 0, 1)
else:
return (0, 1, 0)
sim.set_m(init_m)
fft = demag.compute_field()
exact = demag.compute_exact()
# print fft,exact
print np.max(np.abs(fft - exact))
assert np.max(np.abs(fft - exact)) < 5e-22
def test_demag_fft_exact():
mesh = CuboidMesh(nx=5, ny=3, nz=4)
sim = Sim(mesh)
demag = Demag()
sim.add(demag)
def init_m(pos):
x = pos[0]
if x <= 2:
return (1, 0, 0)
elif x >= 4:
return (0, 0, 1)
else:
return (0, 1, 0)
sim.set_m(init_m)
fft = demag.compute_field()
exact = demag.compute_exact()
# print fft,exact
print np.max(np.abs(fft - exact))
assert np.max(np.abs(fft - exact)) < 5e-22
def relax_system(mesh):
sim = Sim(mesh, name='relax')
sim.mu_s = 1e-23
sim.driver.gamma = 1.76e11
sim.driver.alpha = 1.0
J = 1e-22
exch = UniformExchange(J)
sim.add(exch)
demag = Demag()
sim.add(demag)
sim.set_m(init_m)
ts = np.linspace(0, 5e-10, 101)
for t in ts:
sim.driver.run_until(t)
sim.save_vtk()
np.save('m0.npy', sim.spin)
def test_cuboid_demags_2D():
"""
Comparison of the FFT approach for hexagonal meshes, named
DemagHexagonal, where it is used a system with the double number
of nodes along the x direction (i.e. a mesh with twice the number
of nodes of the original mesh), against the full calculation
of the Demag field
"""
# Number of atoms
N = 15
a = 0.4
mesh = CuboidMesh(a, a, a, N, N, 1, unit_length=1e-9)
mu_s = 2 * const.mu_B
# Centre
xc = (mesh.Lx * 0.5)
yc = (mesh.Ly * 0.5)
sim = Sim(mesh)
sim.mu_s = mu_s
sim.set_m(lambda pos: m_init_2Dvortex(pos, (xc, yc)))
# Brute force demag calculation
sim.add(DemagFull())
sim.get_interaction('DemagFull').compute_field()
# print sim.get_interaction('DemagFull').field
DemagFull_energy = sim.compute_energy() / const.meV
# Demag using the FFT approach
sim2 = Sim(mesh)
sim2.mu_s = mu_s
sim2.set_m(lambda pos: m_init_2Dvortex(pos, (xc, yc)))
sim2.add(Demag())
sim2.get_interaction('Demag').compute_field()
sim2.compute_energy()
demag_fft_energy = sim2.compute_energy() / const.meV
# We compare both energies scaled in meV
assert (DemagFull_energy - demag_fft_energy) < 1e-10
def test_cuboid_demags_1Dchain():
"""
Test a brute force calculation of the demagnetising field, called
DemagFull, based on the sum of the dipolar contributions of the whole
system for every lattice site, against the default FFT approach for the
demag field. We compute the energies scaled in meV.
This test is performed in a cuboid mesh to assure that the DemagFull
library is calculating the same than the default demag function
"""
N = 12
a = 0.4
mesh = CuboidMesh(a, a, a, N, 1, 1, unit_length=1e-9)
mu_s = 2 * const.mu_B
sim = Sim(mesh)
sim.mu_s = mu_s
sim.set_m(lambda pos: m_init_dw(pos, N, a))
# Brute force demag calculation
sim.add(DemagFull())
sim.get_interaction('DemagFull').compute_field()
# print sim.get_interaction('DemagFull').field
DemagFull_energy = sim.compute_energy() / const.meV
# Demag using the FFT approach
sim2 = Sim(mesh)
sim2.mu_s = mu_s
sim2.set_m(lambda pos: m_init_dw(pos, N, a))
sim2.add(Demag())
sim2.get_interaction('Demag').compute_field()
sim2.compute_energy()
demag_fft_energy = sim2.compute_energy() / const.meV
# We compare both energies scaled in meV
assert (DemagFull_energy - demag_fft_energy) < 1e-10
# self.fmm.compute_field(self.theta, self.field)
# self.field *= 1e-7
# return self.field
mesh = fidimag.common.CuboidMesh(nx=Nx,
ny=Ny,
nz=Nz,
dx=1,
dy=1,
dz=1,
unit_length=1e-9)
N = mesh.n
print("Nparticles = {}".format(N))
demagfmm = DemagFMM(order, ncrit, theta=theta)
demagfft = Demag()
demagfull = DemagFull()
sim = fidimag.atomistic.Sim(mesh)
sim.set_m((0, 0, 1), normalise=True)
print(f"Bohr Magnetom = {fidimag.common.constant.mu_B}")
sim.set_mu_s(fidimag.common.constant.mu_B)
sim.add(demagfft)
sim.add(demagfmm)
sim.add(demagfull)
start = time.time()
demagfft.compute_field()
end = time.time()
t = end - start