From c949da2d67ec2bc0d13138415bce7a6a539a82c5 Mon Sep 17 00:00:00 2001
From: James Hensman <james.hensman@gmail.com>
Date: Fri, 11 Jan 2013 17:58:19 +0000
Subject: [PATCH] allowed the gradchecker to return the gradient ratio

Just to help with debugging.
---
 GPy/core/model.py | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/GPy/core/model.py b/GPy/core/model.py
index 183cf0f0..cd37ea33 100644
--- a/GPy/core/model.py
+++ b/GPy/core/model.py
@@ -286,7 +286,7 @@ class model(parameterised):
         return '\n'.join(s)
 
 
-    def checkgrad(self, verbose=False, include_priors=False, step=1e-6, tolerance = 1e-3, *args):
+    def checkgrad(self, verbose=False, include_priors=False, step=1e-6, tolerance = 1e-3, return_ratio=False, *args):
         """
         Check the gradient of the model by comparing to a numerical estimate.
         If the overall gradient fails, invividual components are tested.
@@ -306,12 +306,12 @@ class model(parameterised):
         gradient = self.extract_gradients()
 
         numerical_gradient = (f1-f2)/(2*dx)
-        ratio = (f1-f2)/(2*np.dot(dx,gradient))
+        global_ratio = (f1-f2)/(2*np.dot(dx,gradient))
         if verbose:
-            print "Gradient ratio = ", ratio, '\n'
+            print "Gradient ratio = ", global_ratio, '\n'
             sys.stdout.flush()
 
-        if (np.abs(1.-ratio)<tolerance) and not np.isnan(ratio):
+        if (np.abs(1.-global_ratio)<tolerance) and not np.isnan(global_ratio):
             if verbose:
                 print 'Gradcheck passed'
         else:
@@ -366,5 +366,12 @@ class model(parameterised):
             if verbose:
                 print ''
 
-            return False
-        return True
+            if return_ratio:
+                return global_ratio
+            else:
+                return False
+
+        if return_ratio:
+            return global_ratio
+        else:
+            return True