From 4373157138e85d2dbad9672cef5963a27a3d962c Mon Sep 17 00:00:00 2001
From: Cathy Yeh <cathy@driver.xyz>
Date: Fri, 8 Dec 2017 16:00:52 -0800
Subject: BernoulliAndNode with custom msg passing methods

---
 beliefs/models/belief_update_node_model.py | 39 ++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/beliefs/models/belief_update_node_model.py b/beliefs/models/belief_update_node_model.py
index 667e0f1..4747530 100644
--- a/beliefs/models/belief_update_node_model.py
+++ b/beliefs/models/belief_update_node_model.py
@@ -8,6 +8,7 @@ import networkx as nx
 
 from beliefs.models.base_models import BayesianModel
 from beliefs.factors.bernoulli_or_cpd import BernoulliOrCPD
+from beliefs.factors.bernoulli_and_cpd import BernoulliAndCPD
 
 
 class InvalidLambdaMsgToParent(Exception):
@@ -313,3 +314,41 @@ class BernoulliOrNode(Node):
             if not any(lambda_msg):
                 raise InvalidLambdaMsgToParent
             return self._normalize(lambda_msg)
+
+
+class BernoulliAndNode(Node):
+    def __init__(self,
+                 label_id,
+                 children,
+                 parents):
+        super().__init__(label_id=label_id,
+                         children=children,
+                         parents=parents,
+                         cardinality=2,
+                         cpd=BernoulliAndCPD(label_id, parents))
+
+    def compute_pi_agg(self):
+        if not self.parents:
+            self.pi_agg = self.cpd.values
+        else:
+            pi_msg_values = self.validate_and_return_msgs_received_for_msg_type(MessageType.PI)
+            parents_p1 = [p[1] for p in pi_msg_values]
+            p_1 = reduce(lambda x, y: x*y, parents_p1)
+            p_0 = 1 - p_1
+            self.pi_agg = np.array([p_0, p_1])
+        return self.pi_agg
+
+    def compute_lambda_msg_to_parent(self, parent_k):
+        if np.array_equal(self.lambda_agg, np.ones([self.cardinality])):
+            return np.ones([self.cardinality])
+        else:
+            # TODO: cleanup this validation
+            _ = self.validate_and_return_msgs_received_for_msg_type(MessageType.PI)
+            p1_excluding_k = [msg[1] for par_id, msg in self.pi_received_msgs.items() if par_id != parent_k]
+            p1_product = reduce(lambda x, y: x*y, p1_excluding_k, 1)
+            lambda_0 = self.lambda_agg[0]
+            lambda_1 = self.lambda_agg[0] + (self.lambda_agg[1] - self.lambda_agg[0])*p1_product
+            lambda_msg = np.array([lambda_0, lambda_1])
+            if not any(lambda_msg):
+                raise InvalidLambdaMsgToParent
+            return self._normalize(lambda_msg)
-- 
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