s = assemble(dot(grad(u), N) * v * ds)
M = assemble(w * v * dx)
b = assemble(l)
K = assemble(a)
t = (np.dot(K.array(),uv) - b.array())
q = Function(Q, name='q')
q.vector().set_local(t)
q.vector().apply('insert')
File('output/q.pvd') << q
fx = Function(Q, name='fx')
solve(M, fx.vector(), s)
File('output/fx.pvd') << fx
fig = figure(figsize=(10,5))
ax1 = fig.add_subplot(121)
ax2 = fig.add_subplot(122)
plot_matrix(M.array(), ax1, r'mass matrix $M$', continuous=True)
plot_matrix(K.array(), ax2, r'stiffness matrix $K$', continuous=False)
tight_layout()
show()
return x[0] == 0 and on_boundary
bc = DirichletBC(Q, 0.0, left)
solve(a == l, u, bc)
File('output/u.pvd') << u
uv = u.vector().array()
b = assemble(l).array()
A = assemble(a).array()
t = np.dot(A,uv) - b
q = Function(Q, name='q')
q.vector().set_local(t)
q.vector().apply('insert')
File('output/q.pvd') << q
fig = figure()
ax = fig.add_subplot(111)
plot_matrix(A, ax, r'stiffness matrix $K$', continuous=False)
tight_layout()
show()