def test_hexagonal_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 = HexagonalMesh(a * 0.5, N, N,
unit_length=1e-9,
alignment='square')
# Centre
xc = (mesh.Lx * 0.5)
yc = (mesh.Ly * 0.5)
mu_s = 2 * const.mu_B
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()
sim.get_interaction('DemagFull').field
DemagFull_energy = sim.compute_energy() / const.meV
# Demag using the FFT approach and a larger mesh
sim2 = Sim(mesh)
sim2.mu_s = mu_s
sim2.set_m(lambda pos: m_init_2Dvortex(pos, (xc, yc)))
sim2.add(DemagHexagonal())
sim2.get_interaction('DemagHexagonal').compute_field()
sim2.compute_energy()
demag_2fft_energy = sim2.compute_energy() / const.meV
# We compare both energies scaled in meV
assert (DemagFull_energy - demag_2fft_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
if args.B:
zeeman = Zeeman((0, 0, args.B))
sim.add(zeeman, save_field=True)
if args.k_u:
# Uniaxial anisotropy along + z-axis
sim.add(Anisotropy(args.k_u * const.meV, axis=[0, 0, 1]))
if args.Demag:
print('Using Demag!')
sim.add(DemagHexagonal())
if args.FullDemag:
print('Using Full Demag calculation!')
sim.add(DemagFull())
# -------------------------------------------------------------------------
# -----------------------------------------------------------------------------
# Load magnetisation profile ---------------------------------------------
# Change the skyrmion initial configuration according to the
# chirality of the system (give by the DMI constant)
if args.initial_state_skyrmion_down:
if len(args.initial_state_skyrmion_down) > 1:
pi_factor = args.initial_state_skyrmion_down[1]
else:
pi_factor = 1
# 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
print('fft t = {}'.format(t))