From 3aedf63966e4c8b6f6734d08e116afdfa8ac5d79 Mon Sep 17 00:00:00 2001
From: Max Zwiessele <ibinbei@gmail.com>
Date: Mon, 12 Jan 2015 11:36:53 +0000
Subject: [PATCH] [natural gradients] added natural gradients, usable but not
 analysed

---
 GPy/core/parameterization/parameter_core.py  | 11 +++++++++++
 GPy/core/parameterization/transformations.py | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/GPy/core/parameterization/parameter_core.py b/GPy/core/parameterization/parameter_core.py
index 6add95b0..a15d8d53 100644
--- a/GPy/core/parameterization/parameter_core.py
+++ b/GPy/core/parameterization/parameter_core.py
@@ -683,6 +683,17 @@ class OptimizationHandlable(Indexable):
         [np.put(g, i, c.gradfactor(self.param_array[i], g[i])) for c, i in self.constraints.iteritems() if c != __fixed__]
         if self._has_fixes(): return g[self._fixes_]
         return g
+    
+    def _transform_gradients_non_natural(self, g):
+        """
+        Transform the gradients by multiplying the gradient factor for each
+        constraint to it.
+        """
+        self._highest_parent_.tie.collate_gradient()
+        [np.put(g, i, c.gradfactor_non_natural(self.param_array[i], g[i])) for c, i in self.constraints.iteritems() if c != __fixed__]
+        if self._has_fixes(): return g[self._fixes_]
+        return g
+
 
     @property
     def num_params(self):
diff --git a/GPy/core/parameterization/transformations.py b/GPy/core/parameterization/transformations.py
index 235b9d1c..be08f870 100644
--- a/GPy/core/parameterization/transformations.py
+++ b/GPy/core/parameterization/transformations.py
@@ -42,6 +42,8 @@ class Transformation(object):
             \frac{\frac{\partial L}{\partial f}\left(\left.\partial f(x)}{\partial x}\right|_{x=f^{-1}(f)\right)}
         """
         raise NotImplementedError
+    def gradfactor_non_natural(self, model_param, dL_dmodel_param):
+        return self.gradfactor(model_param, dL_dmodel_param)
     def initialize(self, f):
         """ produce a sensible initial value for f(x)"""
         raise NotImplementedError
@@ -98,6 +100,7 @@ class NormalTheta(Transformation):
         # that the values are ok
         # Before:
         theta[self.var_indices] = np.abs(-.5/theta[self.var_indices])
+        #theta[self.var_indices] = np.exp(-.5/theta[self.var_indices])
         theta[self.mu_indices] *= theta[self.var_indices]
         return theta # which is now {mu, var}
 
@@ -106,6 +109,7 @@ class NormalTheta(Transformation):
         varp = muvar[self.var_indices]
         muvar[self.mu_indices] /= varp
         muvar[self.var_indices] = -.5/varp
+        #muvar[self.var_indices] = -.5/np.log(varp)
 
         return muvar # which is now {theta1, theta2}
 
@@ -250,6 +254,19 @@ class NormalNaturalThroughTheta(NormalTheta):
         #=======================================================================
         return dmuvar # which is now the gradient multiplicator
 
+    def gradfactor_non_natural(self, muvar, dmuvar):
+        mu = muvar[self.mu_indices]
+        var = muvar[self.var_indices]
+        #=======================================================================
+        # theta gradients
+        # This works and the gradient checks!
+        dmuvar[self.mu_indices] *= var
+        dmuvar[self.var_indices] *= 2*(var)**2
+        dmuvar[self.var_indices] += 2*dmuvar[self.mu_indices]*mu
+        #=======================================================================
+
+        return dmuvar # which is now the gradient multiplicator for {theta1, theta2}
+
     def __str__(self):
         return "natgrad"