def solve_poisson_3d(self, n=2):
from fealpy.pde.poisson_3d import CosCosCosData as PDE
from fealpy.mesh import MeshFactory
from fealpy.functionspace import LagrangeFiniteElementSpace
from fealpy.boundarycondition import DirichletBC
pde = PDE()
mf = MeshFactory()
m = 2**n
box = [0, 1, 0, 1, 0, 1]
mesh = mf.boxmesh3d(box, nx=m, ny=m, nz=m, meshtype='tet')
space = LagrangeFiniteElementSpace(mesh, p=1)
gdof = space.number_of_global_dofs()
NC = mesh.number_of_cells()
print('gdof:', gdof, 'NC:', NC)
bc = DirichletBC(space, pde.dirichlet)
uh = space.function()
A = space.stiff_matrix()
A = space.parallel_stiff_matrix(q=1)
M = space.parallel_mass_matrix(q=2)
M = space.mass_matrix()
F = space.source_vector(pde.source)
A, F = bc.apply(A, F, uh)
solver = PETScSolver()
solver.solve(A, F, uh)
error = space.integralalg.L2_error(pde.solution, uh)
print(error)
]
errorMatrix = np.zeros((2, maxit), dtype=np.float)
NDof = np.zeros(maxit, dtype=np.float)
for i in range(maxit):
print("The {}-th computation:".format(i))
space = LagrangeFiniteElementSpace(mesh, p=p)
NDof[i] = space.number_of_global_dofs()
bc = DirichletBC(space, pde.dirichlet)
uh = space.function()
if d == 2:
A = space.stiff_matrix()
elif d == 3:
A = space.parallel_stiff_matrix(q=p)
F = space.source_vector(pde.source)
A, F = bc.apply(A, F, uh)
#ml = pyamg.ruge_stuben_solver(A)
#uh[:] = ml.solve(F, tol=1e-12, accel='cg').reshape(-1)
if d == 2:
uh[:] = spsolve(A, F).reshape(-1)
# elif d==3:
# solver = PETScSolver()
# solver.solve(A, F, uh)
errorMatrix[0, i] = space.integralalg.L2_error(pde.solution, uh)
