def test_DMI_energy_density_3D():
"""Same as above, on a 3D mesh."""
mesh = df.UnitCubeMesh(4, 4, 4)
V = df.VectorFunctionSpace(mesh, "CG", 1, dim=3)
M = Field(V, df.Expression(("-0.5*x[1]", "0.5*x[0]", "1"), degree=1))
Ms = 10
D = 1
dmi = DMI(D)
dmi.setup(M, Field(df.FunctionSpace(mesh, 'DG', 0), Ms))
density = dmi.energy_density()
deviation = np.abs(density - 1.0)
print "3D energy density (expect array of 1):"
print density
print "Max deviation: %g" % np.max(deviation)
assert np.all(deviation < TOL), \
"Max deviation %g, should be zero." % np.max(deviation)
def test_DMI_energy_density_2D():
"""
For a vector field (x, y, z) = 0.5 * (-y, x, c),
the curl is exactly 1.0. (HF)
"""
mesh = df.UnitSquareMesh(4, 4)
V = df.VectorFunctionSpace(mesh, "CG", 1, dim=3)
M = Field(V, value=df.Expression(("-0.5*x[1]", "0.5*x[0]", "1"), degree=1))
Ms = 1
D = 1
dmi = DMI(D)
dmi.setup(M, Field(df.FunctionSpace(mesh, 'DG', 0), Ms))
density = dmi.energy_density()
deviation = np.abs(density - 1.0)
print "2D energy density (expect array of 1):"
print density
print "Max deviation: %g" % np.max(deviation)
assert np.all(deviation < TOL), \
"Max deviation %g, should be zero." % np.max(deviation)