Dear Colleagues,
I appreciate your help. Thank you. 
Regards
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-1a7944c0c864> in <module>
     40     ic.update(y_opt)
     41 
---> 42     alpha.assign(float(alpha) / 2)
     43     print("Set alpha to %f." % float(alpha))
~/opt/Computational_venv/src/firedrake/firedrake/adjoint/constant.py in wrapper(self, *args, **kwargs)
     34                 other = args[0]
     35                 if not isinstance(other, OverloadedType):
---> 36                     other = create_overloaded_object(ndarray(other))
     37 
     38                 block = ConstantAssignBlock(self, other)
TypeError: 'float' object cannot be interpreted as an integer