def main(N, dt, T, theta=0.5):
"""Run bidomain MMA."""
# Exact solutions
u_exact_str = "-cos(pi*x[0])*cos(pi*x[1])*sin(t)/2.0"
v_exact_str = "cos(pi*x[0])*cos(pi*x[1])*sin(t)"
s_exact_str = "-cos(pi*x[0])*cos(pi*x[1])*cos(t)"
# Source term
ac_str = "cos(t)*cos(pi*x[0])*cos(pi*x[1]) + pow(pi, 2)*cos(pi*x[0])*cos(pi*x[1])*sin(t)"
ac_str += " - " + s_exact_str
# Create data
mesh = UnitSquareMesh(N, N)
time = Constant(0.0)
# We choose the FHN parameters such that s=1 and I_s=v
model = SimpleODEModel(mesh)
model.set_initial_conditions(V=0,
S=Expression(s_exact_str, degree=5,
t=0)) # Set initial condition
ps = SplittingSolver.default_parameters()
ps["pde_solver"] = "bidomain"
ps["theta"] = theta
ps["CardiacODESolver"]["scheme"] = "RK4"
ps["enable_adjoint"] = False
ps["BidomainSolver"]["linear_solver_type"] = "direct"
ps["BidomainSolver"]["use_avg_u_constraint"] = True
ps["apply_stimulus_current_to_pde"] = True
stimulus = Expression(ac_str, t=time, dt=dt, degree=5)
M_i = 1.0
M_e = 1.0
heart = cbcbeat.CardiacModel(mesh, time, M_i, M_e, model, stimulus)
splittingsolver = SplittingSolver(heart, params=ps)
# Define exact solution (Note: v is returned at end of time
# interval(s), u is computed at somewhere in the time interval
# depending on theta)
v_exact = Expression(v_exact_str, t=T, degree=3)
u_exact = Expression(u_exact_str, t=T - (1. - theta) * dt, degree=3)
pde_vs_, pde_vs, vur = splittingsolver.solution_fields()
pde_vs_.assign(model.initial_conditions())
solutions = splittingsolver.solve((0, T), dt)
for (t0, t1), (vs_, vs, vur) in solutions:
pass
# Compute errors
v = vs.split(deepcopy=True)[0]
u = vur.split(deepcopy=True)[1]
v_error = errornorm(v_exact, v, "L2", degree_rise=2)
u_error = errornorm(u_exact, u, "L2", degree_rise=2)
return v_error, u_error, mesh.hmin(), dt, T
def main(N, dt, T, theta):
# Create data
mesh = UnitSquareMesh(N, N)
time = Constant(0.0)
ac_str = "cos(t)*cos(pi*x[0])*cos(pi*x[1]) + pow(pi, 2)*cos(pi*x[0])*cos(pi*x[1])*sin(t)"
stimulus = Expression(ac_str, t=time, degree=5)
M_i = 1.
M_e = 1.0
# Set-up solver
params = BidomainSolver.default_parameters()
params["theta"] = theta
params["linear_solver_type"] = "direct"
params["use_avg_u_constraint"] = True
params["enable_adjoint"] = False
solver = BidomainSolver(mesh, time, M_i, M_e, I_s=stimulus, params=params)
# Define exact solution (Note: v is returned at end of time
# interval(s), u is computed at somewhere in the time interval
# depending on theta)
v_exact = Expression("cos(pi*x[0])*cos(pi*x[1])*sin(t)", t=T, degree=3)
u_exact = Expression("-cos(pi*x[0])*cos(pi*x[1])*sin(t)/2.0",
t=T - (1. - theta) * dt,
degree=3)
# Define initial condition(s)
(v_, vu) = solver.solution_fields()
# Solve
solutions = solver.solve((0, T), dt)
for (interval, fields) in solutions:
continue
# Compute errors
(v, u) = vu.split(deepcopy=True)[0:2]
v_error = errornorm(v_exact, v, "L2", degree_rise=2)
u_error = errornorm(u_exact, u, "L2", degree_rise=2)
return [v_error, u_error, mesh.hmin(), dt, T]
def initial_conditions(self):
"Return initial conditions for v and s as an Expression."
return Expression(list(self._initial_conditions.keys()), degree=1,
**self._initial_conditions)