various bugs in adjoint solver

[oskooi]

The following four bugs were discovered using pylint.

1. self.frequencies and self.monitor should be initialized to None.

meep/python/adjoint/objective.py

Lines 26 to 38 in 41548a3

	class EigenmodeCoefficient(ObjectiveQuantitiy):
	def __init__(self,sim,volume,mode,forward=True,kpoint_func=None,**kwargs):
	'''
	'''
	self.sim = sim
	self.volume=volume
	self.mode=mode
	self.forward = 0 if forward else 1
	self.normal_direction = None
	self.kpoint_func = kpoint_func
	self.eval = None
	self.EigenMode_kwargs = kwargs
	return

same for:

meep/python/adjoint/objective.py

Lines 113 to 118 in 41548a3

	class FourierFields(ObjectiveQuantitiy):
	def __init__(self,sim,volume, component):
	self.sim = sim
	self.volume=volume
	self.eval = None
	self.component = component

and:

meep/python/adjoint/objective.py

Lines 170 to 176 in 41548a3

	class Near2FarFields(ObjectiveQuantitiy):
	def __init__(self,sim,Near2FarRegions, far_pt):
	self.sim = sim
	self.Near2FarRegions=Near2FarRegions
	self.eval = None
	self.far_pt = far_pt
	return

2. == should be replaced with =:

meep/python/adjoint/objective.py

Line 61 in 41548a3

k0 == direction_scalar * mp.Vector3(z=1)

3. There are two return statements rather than one:

meep/python/adjoint/filter_source.py

Lines 56 to 57 in 41548a3

	return np.exp(-1j*2*np.pi*f0*t)
	return np.where(n.any() < 0.0 or n.any() > self.N,0,np.exp(-1j*2*np.pi*f0*t))

4. eta is not defined:

meep/python/adjoint/filters.py

Lines 607 to 608 in 41548a3

	case1 = eta*npa.exp(-beta*(eta-x)/eta) - (eta-x)*npa.exp(-beta)
	case2 = 1 - (1-eta)*npa.exp(-beta*(x-eta)/(1-eta)) - (eta-x)*npa.exp(-beta)

[smartalecH]

1. I don't think python always requires initialization of class members to None... we use all of those variables throughout the code and haven't seen any issues.

2. Yes this is a bug -- we haven't ever done tests with EM sources in the z-direction.

3. The rect function here is legacy and not used. We use a nuttall window for the basis function.

4. This along with several other filter bugs is fixed in WIP: Adjoint poynting flux #1398.

[oskooi]

Fixed by #1427, #1590, #1592, and #1593.