def main():
# Initialize
# User-defined parameters
nr = 12 # number of rows
nc = 12 # number of columns
dx = 0.5 # cell spacing
s = 0.001 # source
# k0 = 0.01 # flux coefficient
# Setup
mg = RasterModelGrid(nr, nc, dx)
u = mg.zeros(centering='cell')
interior_cells = mg.get_interior_cells()
dudt = mg.zeros(centering='cell')
#K = mg.zeros(centering='cell')
fx = mg.get_face_x_coords()
fy = mg.get_face_y_coords()
#k = k0 * (fy / max(fy))
#k = k0 * (fx / max(fx))
# print 'k=',k
opt_plot = True
# A "channel"
# k[:] = k0/10.0
# for i in xrange(0, len(k)):
# if fx[i] > 14 and fx[i] < 16 and fy[i] > 14:
# k[i] = k0
# Radially symmetric, exponential decay
k = set_flux_coefficients(mg, dx)
dt = 0.25 * dx**2.0 / max(k) # time step
# print 'dt=',dt
run_time = 100.0
nt = int(round(run_time / dt)) # number of iterations
#ri = raw_input('frog')
# Boundaries
mg.set_noflux_boundaries(True, True, False, True)
# for i in range(0, len(u)):
# u[i] = mg.x(i)
# print 'u=',u
# Process
for i in range(0, nt):
print(i)
g = mg.calculate_face_gradients(u)
q = -k * g
# print 'g=',g
# print 'q=',q
dqds = mg.calculate_flux_divergences(q)
# print 'dqds=',dqds
for c in interior_cells:
dudt[c] = s - dqds[c]
u = u + dudt * dt
u = mg.update_noflux_boundaries(u)
# print 'new u:',u
#plot(x, u)
# draw()
# Finalize
print('Max u = ', max(u))
if opt_plot:
ur = mg.cell_vector_to_raster(u)
#x = 0.5*dx + dx*arange(0, nr)
#x = 0.5*dx + dx*arange(0, nc)
#plot(x, ur[1,:])
contour(ur)
show()
