# Create CG Krylov solver and turn convergence monitoring on
solver = PETSc.KSP().create(MPI.comm_world)
solver.setFromOptions()
# Set matrix operator
solver.setOperators(A)
# Compute solution
solver.setMonitor(lambda ksp, its, rnorm: print(
"Iteration: {}, rel. residual: {}".format(its, rnorm)))
solver.solve(b, u.vector)
solver.view()
# Save solution to XDMF format
file = XDMFFile(MPI.comm_world, "elasticity.xdmf")
file.write(u)
unorm = u.vector.norm()
if MPI.rank(mesh.mpi_comm()) == 0:
print("Solution vector norm:", unorm)
# Save colored mesh partitions in VTK format if running in parallel
# if MPI.size(mesh.mpi_comm()) > 1:
# File("partitions.pvd") << MeshFunction("size_t", mesh, mesh.topology.dim, \
# MPI.rank(mesh.mpi_comm()))
# Project and write stress field to post-processing file
# W = TensorFunctionSpace(mesh, "Discontinuous Lagrange", 0)
# stress = project(sigma(u), V=W)
# File("stress.pvd") << stress
# Output file
file = XDMFFile(MPI.comm_world, "output.xdmf")
# Step in time
t = 0.0
# Check if we are running on CI server and reduce run time
if "CI" in os.environ.keys():
T = 3 * dt
else:
T = 50 * dt
u.vector.copy(result=u0.vector)
u0.vector.ghostUpdate(addv=PETSc.InsertMode.INSERT,
mode=PETSc.ScatterMode.FORWARD)
while (t < T):
t += dt
r = solver.solve(problem, u.vector)
print("Step, num iterations:", int(t / dt), r[0])
u.vector.copy(result=u0.vector)
file.write(u.sub(0), t)
# Within the time stepping loop, the nonlinear problem is solved by
# calling :py:func:`solver.solve(problem,u.vector)<dolfinx.cpp.NewtonSolver.solve>`,
# with the new solution vector returned in :py:func:`u.vector<dolfinx.cpp.Function.vector>`.
# The solution vector associated with ``u`` is copied to ``u0`` at the
# end of each time step, and the ``c`` component of the solution
# (the first component of ``u``) is then written to file.
