def integrate_1d(polynomials, order, scheme = 'gauss'):
'''
Integrates single variables using the Gauss-Legendre or Gauss-Lobatto
quadrature.
Parameters
----------
polynomials : af.Array [number_of_polynomials degree 1 1]
The polynomials to be integrated.
order : int
Order of the quadrature.
scheme : str
Possible options are
- ``gauss`` for using Gauss-Legendre quadrature
- ``lobatto`` for using Gauss-Lobatto quadrature
Returns
-------
integral : af.Array [number_of_polynomials 1 1 1]
The integral for the respective polynomials using the given
quadrature scheme.
'''
integral = 0.0
if scheme == 'gauss':
N_g = order
xi_gauss = af.np_to_af_array(lagrange.gauss_nodes(N_g))
gauss_weights = lagrange.gaussian_weights(N_g)
polyval_gauss = polyval_1d(polynomials, xi_gauss)
integral = af.sum(af.transpose(af.broadcast(multiply,
af.transpose(polyval_gauss),
gauss_weights)), dim = 1)
return integral
elif scheme == 'lobatto':
N_l = order
xi_lobatto = lagrange.LGL_points(N_l)
lobatto_weights = lagrange.lobatto_weights(N_l)
polyval_lobatto = polyval_1d(polynomials, xi_lobatto)
integral = af.sum(af.transpose(af.broadcast(multiply,
af.transpose(polyval_lobatto),
lobatto_weights)), dim = 1)
return integral
else:
return -1.
def test_gauss_weights():
'''
Test to check the gaussian weights calculated.
'''
threshold = 2e-8
analytical_gauss_weights = af.Array([0.23692688505618908, 0.47862867049936647,\
0.5688888888888889, 0.47862867049936647, \
0.23692688505618908
]
)
calculated_gauss_weights = lagrange.gaussian_weights(5)
assert af.max(af.abs(analytical_gauss_weights - calculated_gauss_weights))\
<= threshold
total_time = 2.01
# The c_lax to be used in the Lax-Friedrichs flux.
c_lax = abs(c)
# Array containing the LGL points in xi space.
xi_LGL = lagrange.LGL_points(N_LGL)
#Calculates the weights for the lagrange interpolation
weight_arr = lagrange.weight_arr_fun(xi_LGL)
# N_Gauss number of Gauss nodes.
gauss_points = af.np_to_af_array(lagrange.gauss_nodes(N_quad))
# The Gaussian weights.
gauss_weights = lagrange.gaussian_weights(N_quad)
# The lobatto nodes to be used for integration.
lobatto_quadrature_nodes = lagrange.LGL_points(N_quad)
# The lobatto weights to be used for integration.
lobatto_weights_quadrature = lagrange.lobatto_weights\
(N_quad)
# An array containing the coefficients of the lagrange basis polynomials.
lagrange_coeffs = af.np_to_af_array(\
lagrange.lagrange_polynomials(xi_LGL)[1])
# Refer corresponding functions.
def change_parameters(LGL, Elements, quad, wave='sin'):
'''
Changes the parameters of the simulation. Used only for convergence tests.
Parameters
----------
LGL : int
The new N_LGL.
Elements : int
The new N_Elements.
'''
# The domain of the function.
params.x_nodes = af.np_to_af_array(np.array([-1., 1.]))
# The number of LGL points into which an element is split.
params.N_LGL = LGL
# Number of elements the domain is to be divided into.
params.N_Elements = Elements
# The number quadrature points to be used for integration.
params.N_quad = quad
# Array containing the LGL points in xi space.
params.xi_LGL = lagrange.LGL_points(params.N_LGL)
# The weights of the lgl points
params.weight_arr = lagrange.weight_arr_fun(params.xi_LGL)
# N_Gauss number of Gauss nodes.
params.gauss_points = af.np_to_af_array(lagrange.gauss_nodes\
(params.N_quad))
# The Gaussian weights.
params.gauss_weights = lagrange.gaussian_weights(params.N_quad)
# The lobatto nodes to be used for integration.
params.lobatto_quadrature_nodes = lagrange.LGL_points(params.N_quad)
# The lobatto weights to be used for integration.
params.lobatto_weights_quadrature = lagrange.lobatto_weights\
(params.N_quad)
#The b matrix
params.b_matrix = lagrange.b_matrix_eval()
# A list of the Lagrange polynomials in poly1d form.
#params.lagrange_product = lagrange.product_lagrange_poly(params.xi_LGL)
# An array containing the coefficients of the lagrange basis polynomials.
params.lagrange_coeffs = af.np_to_af_array(\
lagrange.lagrange_polynomials(params.xi_LGL)[1])
# Refer corresponding functions.
params.lagrange_basis_value = lagrange.lagrange_function_value\
(params.lagrange_coeffs)
# While evaluating the volume integral using N_LGL
# lobatto quadrature points, The integration can be vectorized
# and in this case the coefficients of the differential of the
# Lagrange polynomials is required
params.diff_pow = (af.flip(af.transpose(af.range(params.N_LGL - 1) + 1),
1))
params.dl_dxi_coeffs = (af.broadcast(utils.multiply,
params.lagrange_coeffs[:, :-1],
params.diff_pow))
# Obtaining an array consisting of the LGL points mapped onto the elements.
params.element_size = af.sum((params.x_nodes[1] - params.x_nodes[0])\
/ params.N_Elements)
params.elements_xi_LGL = af.constant(0, params.N_Elements, params.N_LGL)
params.elements = utils.linspace(af.sum(params.x_nodes[0]),
af.sum(params.x_nodes[1] - params.element_size),\
params.N_Elements)
params.np_element_array = np.concatenate((af.transpose(params.elements),
af.transpose(params.elements +\
params.element_size)))
params.element_mesh_nodes = utils.linspace(af.sum(params.x_nodes[0]),
af.sum(params.x_nodes[1]),\
params.N_Elements + 1)
params.element_array = af.transpose(af.np_to_af_array\
(params.np_element_array))
params.element_LGL = wave_equation.mapping_xi_to_x(af.transpose\
(params.element_array), params.xi_LGL)
# The minimum distance between 2 mapped LGL points.
params.delta_x = af.min(
(params.element_LGL - af.shift(params.element_LGL, 1, 0))[1:, :])
# dx_dxi for elements of equal size.
params. dx_dxi = af.mean(wave_equation.dx_dxi_numerical((params.element_mesh_nodes[0 : 2]),\
params.xi_LGL))
# The value of time-step.
params.delta_t = params.delta_x / (4 * params.c)
# Array of timesteps seperated by delta_t.
params.time = utils.linspace(
0,
int(params.total_time / params.delta_t) * params.delta_t,
int(params.total_time / params.delta_t))
# Initializing the amplitudes. Change u_init to required initial conditions.
if (wave == 'sin'):
params.u_init = af.sin(2 * np.pi * params.element_LGL)
if (wave == 'gaussian'):
params.u_init = np.e**(-(params.element_LGL)**2 / 0.4**2)
params.u = af.constant(0, params.N_LGL, params.N_Elements, params.time.shape[0],\
dtype = af.Dtype.f64)
params.u[:, :, 0] = params.u_init
return
def __init__(self, N_LGL, N_quad, x_nodes, N_elements, c, total_time, wave,
c_x, c_y, courant, mesh_file, total_time_2d):
'''
Initializes the variables using the user parameters.
Parameters
----------
N_LGL : int
Number of LGL points(for both :math:`2D` and :math:`1D` wave
equation solver).
N_quad : int
Number of the quadrature points to use in Gauss-Lobatto or
Gauss-Legendre quadrature.
x_nodes : af.Array [2 1 1 1]
:math:`x` nodes for the :math:`1D` wave equation elements.
N_elements : int
Number of elements in a :math:`1D` domain.
c : float64
Wave speed for 1D wave equation.
total_time : float64
Total time for which :math:`1D` wave equation is to be
evolved.
wave : str
Used to set u_init to ``sin`` or ``cos``.
c_x : float64
:math:`x` component of wave speed for a :math:`2D` wave.
c_y : float64
:math:`y` component of wave speed for a :math:`2D` wave.
courant : float64
Courant parameter used for the time evolution of the wave.
mesh_file : str
Path of the mesh file for the 2D wave equation.
total_time_2d : float64
Total time for which the wave is to propogated.
Returns
-------
None
'''
self.xi_LGL = lagrange.LGL_points(N_LGL)
# N_Gauss number of Gauss nodes.
self.gauss_points = af.np_to_af_array(lagrange.gauss_nodes(N_quad))
# The Gaussian weights.
self.gauss_weights = lagrange.gaussian_weights(N_quad)
# The lobatto nodes to be used for integration.
self.lobatto_quadrature_nodes = lagrange.LGL_points(N_quad)
# The lobatto weights to be used for integration.
self.lobatto_weights_quadrature = lagrange.lobatto_weights(N_quad)
# An array containing the coefficients of the lagrange basis polynomials.
self.lagrange_coeffs = lagrange.lagrange_polynomial_coeffs(self.xi_LGL)
self.lagrange_basis_value = lagrange.lagrange_function_value(
self.lagrange_coeffs, self.xi_LGL)
self.diff_pow = af.flip(af.transpose(af.range(N_LGL - 1) + 1), 1)
self.dl_dxi_coeffs = af.broadcast(utils.multiply,
self.lagrange_coeffs[:, :-1],
self.diff_pow)
self.element_size = af.sum((x_nodes[1] - x_nodes[0]) / N_elements)
self.elements_xi_LGL = af.constant(0, N_elements, N_LGL)
self.elements = utils.linspace(af.sum(x_nodes[0]),
af.sum(x_nodes[1] - self.element_size),
N_elements)
self.np_element_array = np.concatenate(
(af.transpose(self.elements),
af.transpose(self.elements + self.element_size)))
self.element_mesh_nodes = utils.linspace(af.sum(x_nodes[0]),
af.sum(x_nodes[1]),
N_elements + 1)
self.element_array = af.transpose(
af.interop.np_to_af_array(self.np_element_array))
self.element_LGL = wave_equation.mapping_xi_to_x(
af.transpose(self.element_array), self.xi_LGL)
# The minimum distance between 2 mapped LGL points.
self.delta_x = af.min(
(self.element_LGL - af.shift(self.element_LGL, 1, 0))[1:, :])
# dx_dxi for elements of equal size.
self.dx_dxi = af.mean(
wave_equation.dx_dxi_numerical(self.element_mesh_nodes[0:2],
self.xi_LGL))
# The value of time-step.
self.delta_t = self.delta_x / (4 * c)
# Array of timesteps seperated by delta_t.
self.time = utils.linspace(
0,
int(total_time / self.delta_t) * self.delta_t,
int(total_time / self.delta_t))
# Initializing the amplitudes. Change u_init to required initial conditions.
if (wave == 'sin'):
self.u_init = af.sin(2 * np.pi * self.element_LGL)
if (wave == 'gaussian'):
self.u_init = np.e**(-(self.element_LGL)**2 / 0.4**2)
self.test_array = af.np_to_af_array(np.array(self.u_init))
# The parameters below are for 2D advection
# -----------------------------------------
########################################################################
#######################2D Wave Equation#################################
########################################################################
self.xi_i = af.flat(af.transpose(af.tile(self.xi_LGL, 1, N_LGL)))
self.eta_j = af.tile(self.xi_LGL, N_LGL)
self.dLp_xi_ij = af.moddims(
af.reorder(
af.tile(utils.polyval_1d(self.dl_dxi_coeffs, self.xi_i), 1, 1,
N_LGL), 1, 2, 0), N_LGL**2, 1, N_LGL**2)
self.Lp_xi_ij = af.moddims(
af.reorder(
af.tile(utils.polyval_1d(self.lagrange_coeffs, self.xi_i), 1,
1, N_LGL), 1, 2, 0), N_LGL**2, 1, N_LGL**2)
self.dLq_eta_ij = af.tile(
af.reorder(utils.polyval_1d(self.dl_dxi_coeffs, self.eta_j), 1, 2,
0), 1, 1, N_LGL)
self.Lq_eta_ij = af.tile(
af.reorder(utils.polyval_1d(self.lagrange_coeffs, self.eta_j), 1,
2, 0), 1, 1, N_LGL)
self.dLp_Lq = self.Lq_eta_ij * self.dLp_xi_ij
self.dLq_Lp = self.Lp_xi_ij * self.dLq_eta_ij
self.Li_Lj_coeffs = wave_equation_2d.Li_Lj_coeffs(N_LGL)
self.delta_y = self.delta_x
self.delta_t_2d = courant * self.delta_x * self.delta_y \
/ (self.delta_x * c_x + self.delta_y * c_y)
self.c_lax_2d_x = c_x
self.c_lax_2d_y = c_y
self.nodes, self.elements = msh_parser.read_order_2_msh(mesh_file)
self.x_e_ij = af.np_to_af_array(
np.zeros([N_LGL * N_LGL, len(self.elements)]))
self.y_e_ij = af.np_to_af_array(
np.zeros([N_LGL * N_LGL, len(self.elements)]))
for element_tag, element in enumerate(self.elements):
self.x_e_ij[:, element_tag] = isoparam.isoparam_x_2D(
self.nodes[element, 0], self.xi_i, self.eta_j)
self.y_e_ij[:, element_tag] = isoparam.isoparam_y_2D(
self.nodes[element, 1], self.xi_i, self.eta_j)
self.u_e_ij = af.sin(self.x_e_ij * 2 * np.pi + self.y_e_ij * 4 * np.pi)
# Array of timesteps seperated by delta_t.
self.time_2d = utils.linspace(
0,
int(total_time_2d / self.delta_t_2d) * self.delta_t_2d,
int(total_time_2d / self.delta_t_2d))
self.sqrt_det_g = wave_equation_2d.sqrt_det_g(self.nodes[self.elements[0]][:, 0], \
self.nodes[self.elements[0]][:, 1], np.array(self.xi_i), np.array(self.eta_j))
self.elements_nodes = (af.reorder(
af.transpose(af.np_to_af_array(self.nodes[self.elements[:]])), 0,
2, 1))
self.sqrt_g = af.reorder(wave_equation_2d.trial_sqrt_det_g(self.elements_nodes[:, 0, :],\
self.elements_nodes[:, 1, :], self.xi_i, self.eta_j), 0, 2, 1)
return