Added prefered_initial_step_size to LineSearch class.

nifty/minimization/line_searching/line_search.py

@@ -31,6 +31,7 @@ class LineSearch(Loggable, object):
         self.pk = None
         self.line_energy = None
         self.f_k_minus_1 = None
+        self.prefered_initial_step_size = None
 
     def _set_line_energy(self, energy, pk, f_k_minus_1=None):
         """

nifty/minimization/line_searching/line_search_strong_wolfe.py

@@ -64,7 +64,9 @@ class LineSearchStrongWolfe(LineSearch):
 
         # set alphas
         alpha0 = 0.
-        if old_phi_0 is not None and phiprime_0 != 0:
+        if self.prefered_initial_step_size is not None:
+            alpha1 = self.prefered_initial_step_size
+        elif old_phi_0 is not None and phiprime_0 != 0:
             alpha1 = min(1.0, 1.01*2*(phi_0 - old_phi_0)/phiprime_0)
             if alpha1 < 0:
                 alpha1 = 1.0

nifty/minimization/relaxed_newton.py

 # -*- coding: utf-8 -*-
 
 from .quasi_newton_minimizer import QuasiNewtonMinimizer
+from .line_searching import LineSearchStrongWolfe
 
 
 class RelaxedNewton(QuasiNewtonMinimizer):
+    def __init__(self, line_searcher=LineSearchStrongWolfe(), callback=None,
+                 convergence_tolerance=1E-4, convergence_level=3,
+                 iteration_limit=None):
+        super(RelaxedNewton, self).__init__(
+                                line_searcher=line_searcher,
+                                callback=callback,
+                                convergence_tolerance=convergence_tolerance,
+                                convergence_level=convergence_level,
+                                iteration_limit=iteration_limit)
+
+        self.line_searcher.prefered_initial_step_size = 1.
+
     def _get_descend_direction(self, energy):
         gradient = energy.gradient
         curvature = energy.curvature