def analytical_solution(self, type, time):
if type == "Positions":
analytical_solution = (np.hstack((self.init_pos, self.final_pos)) +
np.sin(np.pi * time) / np.pi**2)
elif type == "Velocity":
analytical_solution = (0.0 * np.hstack(
(self.init_pos, self.final_pos)) +
np.cos(np.pi * time) / np.pi)
elif type == "Directors":
from elastica._rotations import _rotate
final_angle = self.omega_value * time + 0.5 * 0.1 * np.pi * time**2
axis = np.array([0.0, 0.0,
1.0]).reshape(3, 1) # There is only one director
analytical_solution = _rotate(self.init_dir, final_angle, axis)
return analytical_solution
def rotate(matrix, scale, axis):
"""
This function takes single or multiple frames as matrix. Then rotates these frames
around a single axis for all frames, or can rotate each frame around its own
rotation axis as defined by user. Scale determines how much frames rotates
around this axis.
matrix: minimum shape = dim**2x1, supports shape = 3x3xn
axis: minimum dim = 3x1, 1x3, supports dim = 3xn, nx3
scale: minimum float, supports 1D vectors also dim = n
"""
matrix = format_matrix_shape(matrix)
axis = format_vector_shape(axis)
return _rotate(matrix, scale, axis)
def analytical_solution(self, type, time):
if type == "Positions":
analytical_solution = (np.hstack(
(self.init_pos)) + np.sin(np.pi * time) / np.pi**2)
elif type == "Velocity":
analytical_solution = (0.0 * np.hstack(
(self.init_pos)) + np.cos(np.pi * time) / np.pi)
elif type == "Directors":
final_angle = self.omega_value * time + 0.5 * 0.1 * np.pi * time**2
axis = np.array([0.0, 0.0,
1.0]).reshape(3, 1) # There is only one director
# Reshaping done to prevent numba equivalent to complain
# While we can prevent it here, its' done to make the front end testing scripts "look"
# nicer and cleaner
analytical_solution = _rotate(self.init_dir, final_angle,
axis).reshape(-1, 1)
return analytical_solution
def __add__(self, scaled_derivative_state):
"""overloaded + operator, useful in state.k1 = state + dt * deriv_state
The add for directors is customized to reflect Rodrigues' rotation
formula.
Parameters
----------
scaled_derivative_state : np.ndarray with dt * (v, ω, dv/dt, dω/dt)
,as returned from _DerivativeState's __mul__ method
Returns
-------
state : new _State object with modified data (copied)
Caveats
-------
Note that the argument is not a `other` _State object but is rather
assumed to be a `np.ndarray` from calling _DerivativeState's __mul__
method. This reflects the most common use-case in time-steppers
"""
# x += v*dt
position_collection = (
self.position_collection + scaled_derivative_state[..., : self.n_nodes]
)
# Devs : see `_State.__iadd__` for reasons why we do matmul here
director_collection = _rotate(
self.director_collection,
1.0,
scaled_derivative_state[..., self.n_nodes : self.n_kinematic_rates],
)
# (v,ω) += (dv/dt, dω/dt)*dt
kinematic_rate_collection = (
self.kinematic_rate_collection
+ scaled_derivative_state[..., self.n_kinematic_rates :]
)
return _State(
self.n_nodes - 1,
position_collection,
director_collection,
kinematic_rate_collection,
)
def test_rotate_correctness():
blocksize = 16
def get_aligned_director_collection(theta_collection):
sins = np.sin(theta_collection)
coss = np.cos(theta_collection)
# Get basic director out, then modify it as you like
dir = np.tile(np.eye(3).reshape(3, 3, 1), blocksize)
dir[0, 0, ...] = coss
# Flip signs on [0,1] and [1,0] to go from our row-wise
# representation to the more commonly used
# columnwise representation, for similar reasons metioned
# before
dir[0, 1, ...] = sins
dir[1, 0, ...] = -sins
dir[1, 1, ...] = coss
return dir
base_angle = np.deg2rad(np.linspace(0.0, 90.0, blocksize))
rotated_by = np.deg2rad(15.0) + 0.0 * base_angle
rotated_about = np.array([0.0, 0.0, 1.0]).reshape(-1, 1)
director_collection = get_aligned_director_collection(base_angle)
axis_collection = np.tile(rotated_about, blocksize)
axis_collection *= rotated_by
dt = 1.0
test_rotated_director_collection = _rotate(director_collection, dt,
axis_collection)
correct_rotation = rotated_by + 1.0 * base_angle
correct_rotated_director_collection = get_aligned_director_collection(
correct_rotation)
assert test_rotated_director_collection.shape == (3, 3, blocksize)
assert_allclose(
test_rotated_director_collection,
correct_rotated_director_collection,
atol=Tolerance.atol(),
)
