From 1e64a442e78b5e471b2f573295bd9a747b7c6c3f Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex.auvolat@ens.fr>
Date: Fri, 24 Jul 2015 10:27:15 -0400
Subject: Memory net refactoring

---
 model/memory_network.py | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

(limited to 'model/memory_network.py')

diff --git a/model/memory_network.py b/model/memory_network.py
index e7ba51c..84a8edf 100644
--- a/model/memory_network.py
+++ b/model/memory_network.py
@@ -14,11 +14,58 @@ import error
 from model import ContextEmbedder
 
 class MemoryNetworkBase(Initializable):
-    def __init__(self, config, **kwargs):
+    def __init__(self, config, prefix_encoder, candidate_encoder, **kwargs):
         super(MemoryNetworkBase, self).__init__(**kwargs)
 
+        self.prefix_encoder = prefix_encoder
+        self.candidate_encoder = candidate_encoder
         self.config = config
 
+        self.softmax = Softmax()
+        self.children = [ self.softmax, prefix_encoder, candidate_encoder ]
+
+        self.inputs = self.prefix_encoder.apply.inputs \
+                      + ['candidate_%s'%x for x in self.candidate_encoder.apply.inputs]
+
+    def candidate_destination(**kwargs):
+        return tensor.concatenate(
+                (tensor.shape_padright(kwargs['candidate_last_k_latitude'][:,-1]),
+                 tensor.shape_padright(kwargs['candidate_last_k_longitude'][:,-1])),
+                axis=1)
+
+    @application(outputs=['cost'])
+    def cost(self, **kwargs):
+        y_hat = self.predict(**kwargs)
+        y = tensor.concatenate((kwargs['destination_latitude'][:, None],
+                                kwargs['destination_longitude'][:, None]), axis=1)
+
+        return error.erdist(y_hat, y).mean()
+
+    @application(outputs=['destination'])
+    def predict(self, **kwargs):
+        prefix_representation = self.prefix_encoder.apply(
+                { x: kwargs[x] for x in self.prefix_encoder.apply.inputs })
+        candidate_representatin = self.candidate_encoder.apply(
+                { x: kwargs['candidate_'+x] for x in self.candidate_encoder.apply.inputs })
+
+        if self.config.normalize_representation:
+            prefix_representation = prefix_representation \
+                    / tensor.sqrt((prefix_representation ** 2).sum(axis=1, keepdims=True))
+            candidate_representation = candidate_representation \
+                    / tensor.sqrt((candidate_representation ** 2).sum(axis=1, keepdims=True))
+
+        similarity_score = tensor.dot(prefix_representation, candidate_representation.T)
+        similarity = self.softmax.apply(similarity_score)
+
+        return tensor.dot(similarity, self.candidate_destination(**kwargs))
+
+    @predict.property('inputs')
+    def predict_inputs(self):
+        return self.inputs
+
+    @cost.property('inputs')
+    def cost_inputs(self):
+        return self.inputs + ['destination_latitude', 'destination_longitude']
 
 class StreamBase(object):
     def __init__(self, config):
-- 
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