#-------------------------
# ts:
#-------------------------
# alternative way to get the top/bottom middle dof using slicing of FEGrid:
# i.e. get the element which is placed right for the center and then get the lower left node
#bottom_middle_dof = domain[shape[0]/2, 0, 0, 0].dofs[0,0,1]
#top_middle_dof = domain[shape[0]/2,-1, 0,-1].dofs[0,0,1]
top_middle_dofs, top_middle_dof_points = domain.get_top_middle_dofs()
top_middle_dof = top_middle_dofs[0,1]
print 'top_middle_dof', top_middle_dof
bottom_middle_dofs, bottom_middle_dof_points = domain.get_bottom_middle_dofs()
bottom_middle_dof = bottom_middle_dofs[0,1]
print 'bottom_middle_dof', bottom_middle_dof
tstepper = TS( dof_resultants = True,
sdomain = domain,
bcond_list = [ BCDof( var='u', value = u_max, dof = top_middle_dof ),
BCDofGroup( var='u', value = 0., dims = [0,1],
get_dof_method = domain.get_bottom_left_dofs ),
BCDofGroup( var='u', value = 0., dims = [1],
get_dof_method = domain.get_bottom_right_dofs ) ],
rtrace_list = [
RTraceGraph(name = 'Fi at top over u at bottom (iteration)' ,
var_y = 'F_int', idx_y = top_middle_dof,
var_x = 'U_k', idx_x = bottom_middle_dof,
transform_x = '-x',
