more documentation

nifty/energies/quadratic_energy.py

@@ -4,6 +4,8 @@ from nifty.energies.memoization import memo
 
 class QuadraticEnergy(Energy):
     """The Energy for a quadratic form.
+    The most important aspect of this energy is that its curvature must be
+    position-independent.
     """
 
     def __init__(self, position, A, b):

nifty/minimization/iteration_controller.py

@@ -24,6 +24,22 @@ import numpy as np
 from keepers import Loggable
 
 class IterationController(Loggable, object):
+    """The abstract base class for all iteration controllers.
+    An iteration controller is an object that monitors the progress of a
+    minimization iteration. At the begin of the minimization, its start()
+    method is called with the energy object at the initial position.
+    Afterwards, its check() method is called during every iteration step with
+    the energy object describing the current position.
+    Based on that information, the iteration controller has to decide whether
+    iteration needs to progress further (in this case it returns CONTINUE), or
+    if sufficient convergence has been reached (in this case it returns
+    CONVERGED), or if some error has been detected (then it returns ERROR).
+
+    The concrete convergence criteria can be chosen by inheriting from this
+    class; the implementer has full flexibility to use whichever criteria are
+    appropriate for a particular problem - as ong as they can be computed from
+    the information passed to the controller during the iteration process.
+    """
 
     __metaclass__ = NiftyMeta
 

nifty/minimization/relaxed_newton.py

@@ -21,7 +21,6 @@ from .line_searching import LineSearchStrongWolfe
 
 
 class RelaxedNewton(DescentMinimizer):
-
     def __init__(self, controller, line_searcher=LineSearchStrongWolfe()):
         super(RelaxedNewton, self).__init__(
                                 controller=controller,