def test_geodesic_distance():
"""
We will measure the distance between a spin in the +z direction and a spin
at the -z direction. The great-circle distance (distance on the unit
sphere) should be PI, since the perimeter is 2PI
The other distance is between a spin in the [0, 1, 0] direction and another
one in the [-1, 0, 0] direction. The arc length should be PI/2
"""
# Degrees of freedom in Cartesian coordinates
A = np.array([0, 0, 1.])
B = np.array([0, 0, -1.])
n_dofs_image = 3
# The material array only indicates the lattice/mesh sites where
# there is material (mu_s or M_s larger than zero)
material = np.array([1]).astype(np.int32)
n_dofs_image_material = 3
d = nebm_geodesic.geodesic_distance(A, B, n_dofs_image,
material, n_dofs_image_material
)
assert np.abs(d - np.pi) < 1e-5
# The other two spins:
A = np.array([0, 1, 0.])
B = np.array([-1, 0, 0.])
d = nebm_geodesic.geodesic_distance(A, B, n_dofs_image,
material, n_dofs_image_material
)
assert np.abs(d - np.pi * 0.5) < 1e-5
def compute_distances(self, A, B):
"""
Compute the distance between corresponding images of the bands A and B
A B
[ [image_0] [ [image_0]
[image_1] - [image_1]
..self. ...
] ]
"""
A.shape = (-1, self.n_dofs_image)
B.shape = (-1, self.n_dofs_image)
distances = np.zeros(len(A))
for i in range(len(distances)):
distances[i] = nebm_geodesic.geodesic_distance(
A[i], B[i], self.n_dofs_image, self._material_int,
self.n_dofs_image_material)
A.shape = (-1)
B.shape = (-1)
return distances
def compute_distances(self, A, B):
"""
Compute the distance between corresponding images of the bands A and B
A B
[ [image_0] [ [image_0]
[image_1] - [image_1]
..self. ...
] ]
"""
A.shape = (-1, self.n_dofs_image)
B.shape = (-1, self.n_dofs_image)
distances = np.zeros(len(A))
for i in range(len(distances)):
distances[i] = nebm_geodesic.geodesic_distance(A[i], B[i],
self.n_dofs_image,
self._material_int,
self.n_dofs_image_material
)
A.shape = (-1)
B.shape = (-1)
return distances