def mass_matrix_V0_1d(p, Nbase, T, bc):
"""
Computes the 1d mass matrix of the space V0.
Parameters
----------
p : int
spline degree
Nbase : int
number of spline functions
T : np.array
knot vector
bc : boolean
boundary conditions (True = periodic, False = homogeneous Dirichlet)
Returns
-------
mass : 2d np.array
mass matrix in V0
"""
if bc == True:
bcon = 1
Nbase_0 = Nbase - p
else:
bcon = 0
Nbase_0 = Nbase
el_b = inter.construct_grid_from_knots(p, Nbase, T)
ne = len(el_b) - 1
pts_loc, wts_loc = np.polynomial.legendre.leggauss(p + 1)
pts, wts = inter.construct_quadrature_grid(ne, p + 1, pts_loc, wts_loc,
el_b)
d = 0
basis = inter.eval_on_grid_splines_ders(p, Nbase, p + 1, d, T, pts)
mass = np.zeros((Nbase_0, Nbase_0))
for ie in range(ne):
for il in range(p + 1):
for jl in range(p + 1):
i = ie + il
j = ie + jl
value = 0.
for g in range(p + 1):
value += wts[g, ie] * basis[il, 0, g, ie] * basis[jl, 0, g,
ie]
mass[i % Nbase_0, j % Nbase_0] += value
return mass[(1 - bcon):Nbase_0 - (1 - bcon),
(1 - bcon):Nbase_0 - (1 - bcon)]
def PI_1_1d(fun, p, Nbase, T, bc):
"""
Computes the FEM coefficient of the function 'fun' projected on the space V1.
Parameters
----------
fun : callable
the function to be projected
p : int
spline degree
Nbase : int
number of spline functions
T : np.array
knot vector
Returns
-------
vec : np.array
the FEM coefficients
"""
# compute greville points
grev = inter.compute_greville(p, Nbase, T)
# compute quadrature grid
pts_loc, wts_loc = np.polynomial.legendre.leggauss(p)
pts, wts = inter.construct_quadrature_grid(Nbase - 1, p, pts_loc, wts_loc,
grev)
# compute element boundaries to get length of domain for periodic boundary conditions
el_b = inter.construct_grid_from_knots(p, Nbase, T)
# assemble vector of histopolation problem at greville points
rhs = integrate_1d(pts % el_b[-1], wts, fun)
# assemble histopolation matrix
D = histopolation_matrix_1d(p, Nbase, T, grev, bc)
# apply boundary conditions
if bc == True:
lower = int(np.ceil(p / 2) - 1)
upper = -int(np.floor(p / 2))
else:
lower = 0
upper = Nbase - 1
rhs = rhs[lower:upper]
# solve histopolation problem
vec = np.linalg.solve(D, rhs)
return vec
def L2_prod_V1_1d(fun, p, Nbase, T):
"""
Computes the L2 scalar product of the function 'fun' with the B-splines of the space V1
using a quadrature rule of order p.
Parameters
----------
fun : callable
function for scalar product
p : int
spline degree
Nbase : int
number of spline functions
T : np.array
knot vector
Returns
-------
f_int : np.array
the result of the integration with each basis function
"""
el_b = inter.construct_grid_from_knots(p, Nbase, T)
ne = len(el_b) - 1
pts_loc, wts_loc = np.polynomial.legendre.leggauss(p)
pts, wts = inter.construct_quadrature_grid(ne, p, pts_loc, wts_loc, el_b)
t = T[1:-1]
d = 0
basis = inter.eval_on_grid_splines_ders(p - 1, Nbase - 1, p, d, t, pts)
f_int = np.zeros(Nbase - 1)
for ie in range(ne):
for il in range(p):
i = ie + il
value = 0.
for g in range(p):
value += wts[g, ie] * fun(pts[g, ie]) * basis[il, 0, g, ie]
f_int[i] += value * p / (t[i + p] - t[i])
return f_int
def normalization_V1_1d(p, Nbase, T):
"""
Computes the normalization of all basis functions of the space V1.
Parameters
----------
p : int
spline degree
Nbase : int
number of spline functions
T : np.array
knot vector
Returns
----------
norm: np.array
the integral of each basis function over the entire computational domain
"""
el_b = inter.construct_grid_from_knots(p, Nbase, T)
Nel = len(el_b) - 1
t = T[1:-1]
pts_loc, wts_loc = np.polynomial.legendre.leggauss(p - 1)
pts, wts = inter.construct_quadrature_grid(Nel, p - 1, pts_loc, wts_loc,
el_b)
basis = inter.eval_on_grid_splines_ders(p - 1, Nbase - 1, p - 1, 0, t, pts)
norm = np.zeros(Nbase - 1)
for ie in range(Nel):
for il in range(p):
i = ie + il
value = 0.
for g in range(p - 1):
value += wts[g, ie] * basis[il, 0, g, ie]
norm[i] += value * p / (t[i + p] - t[i])
return norm
def histopolation_matrix_1d(p, Nbase, T, grev, bc):
"""
Computest the 1d histopolation matrix.
Parameters
----------
p : int
spline degree
Nbase : int
number of spline functions
T : np.array
knot vector
grev : np.array
greville points
bc : boolean
boundary conditions (True = periodic, False = homogeneous Dirichlet)
Returns
-------
D : 2d np.array
histopolation matrix
"""
el_b = inter.construct_grid_from_knots(p, Nbase, T)
Nel = len(el_b) - 1
if bc == False:
return inter.histopolation_matrix(p, Nbase, T, grev)
else:
if p % 2 != 0:
dx = el_b[-1] / Nel
ne = Nbase - 1
pts_loc, wts_loc = np.polynomial.legendre.leggauss(p - 1)
pts, wts = inter.construct_quadrature_grid(ne, p - 1, pts_loc,
wts_loc, grev)
col_quad = inter.collocation_matrix(
p - 1, ne, T[1:-1], (pts % el_b[-1]).flatten()) / dx
D = np.zeros((ne, ne))
for i in range(ne):
for j in range(ne):
for k in range(p - 1):
D[i, j] += wts[k, i] * col_quad[i + ne * k, j]
lower = int(np.ceil(p / 2) - 1)
upper = -int(np.floor(p / 2))
D[:, :(p - 1)] += D[:, -(p - 1):]
D = D[lower:upper, :D.shape[1] - (p - 1)]
return D
else:
dx = el_b[-1] / Nel
ne = Nbase - 1
a = grev
b = grev + dx / 2
c = np.vstack((a, b)).reshape((-1, ), order='F')[:-1]
pts_loc, wts_loc = np.polynomial.legendre.leggauss(p - 1)
pts, wts = inter.construct_quadrature_grid(2 * ne, p - 1, pts_loc,
wts_loc, c)
col_quad = inter.collocation_matrix(
p - 1, ne, T[1:-1], (pts % el_b[-1]).flatten()) / dx
D = np.zeros((ne, ne))
for il in range(2 * ne):
i = int(np.floor(il / 2))
for j in range(ne):
for k in range(p - 1):
D[i, j] += wts[k, il] * col_quad[il + 2 * ne * k, j]
lower = int(np.ceil(p / 2) - 1)
upper = -int(np.floor(p / 2))
D[:, :(p - 1)] += D[:, -(p - 1):]
D = D[lower:upper, :D.shape[1] - (p - 1)]
return D
