make parameters into function arguments

This patch makes all parameters into arguments of main so that they can be
configured from the command line (though not via run.sh). This makes it
possible, for example, to experiment with different timesteps on either half of
the simulation.

partitioned-heat-conduction/nutils/heat.py

@@ -7,25 +7,15 @@
 import precice
 
 
-def main(side='Dirichlet'):
-    print("Running nutils")
-
-    # domain size
-    y_bottom, y_top = 0, 1
-    x_left, x_right = 0, 2
-    x_coupling = 1  # x coordinate of coupling interface
-    degree = 1  # linear finite elements
-    n = 10  # number of mesh vertices per dimension
-    timestep = 0.1
+def main(side='Dirichlet', n=10, degree=1, timestep=.1, alpha=3., beta=1.3):
 
     if side == 'Dirichlet':
-        x_grid = np.linspace(x_left, x_coupling, n)
+        x_grid = np.linspace(0, 1, n)
     elif side == 'Neumann':
-        x_grid = np.linspace(x_coupling, x_right, n)
+        x_grid = np.linspace(1, 2, n)
     else:
         raise Exception('invalid side {!r}'.format(side))
-
-    y_grid = np.linspace(y_bottom, y_top, n)
+    y_grid = np.linspace(0, 1, n)
 
     # define the Nutils mesh
     domain, geom = mesh.rectilinear([x_grid, y_grid])
@@ -36,8 +26,8 @@ def main(side='Dirichlet'):
     ns = function.Namespace()
     ns.x = geom
     ns.basis = domain.basis('std', degree=degree)
-    ns.alpha = 3  # parameter of problem
-    ns.beta = 1.3  # parameter of problem
+    ns.alpha = alpha  # parameter of problem
+    ns.beta = beta  # parameter of problem
     ns.u = 'basis_n ?lhs_n'  # solution
     ns.dudt = 'basis_n (?lhs_n - ?lhs0_n) / ?dt'  # time derivative
     ns.flux = 'basis_n ?fluxdofs_n'  # heat flux