From e244e22c6ac37980507d8b836bccf8407db6ded5 Mon Sep 17 00:00:00 2001
From: Manohar Paluri <balamanohar@gmail.com>
Date: Mon, 7 Dec 2009 07:12:01 +0000
Subject: [PATCH] added probability function that computes the probability of a
  BinaryBayesNet  given a config.

---
 cpp/testBinaryBayesNet.cpp | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/cpp/testBinaryBayesNet.cpp b/cpp/testBinaryBayesNet.cpp
index 2b67939e7..ee4fc18f3 100644
--- a/cpp/testBinaryBayesNet.cpp
+++ b/cpp/testBinaryBayesNet.cpp
@@ -31,6 +31,18 @@ using namespace gtsam;
 /** A Bayes net made from binary conditional probability tables */
 typedef BayesNet<BinaryConditional> BinaryBayesNet;
 
+
+double probability( BinaryBayesNet & bbn, map<string,bool> & config)
+{
+	double result = 1.0;
+	BinaryBayesNet::const_iterator it = bbn.begin();
+	while( it != bbn.end() ){
+		result *= (*it)->probability(config);
+		it++;
+	}
+	return result;
+}
+
 /************************************************************************** */
 TEST( BinaryBayesNet, constructor )
 {
@@ -40,19 +52,19 @@ TEST( BinaryBayesNet, constructor )
 	// p(x|y=1) = 0.6
 
 	map<string,bool> config;
-	config["y"] = true;
-	config["x"] = true;
+	config["y"] = false;
+	config["x"] = false;
 	// unary conditional for y
 	boost::shared_ptr<BinaryConditional> py(new BinaryConditional("y",0.2));
 	py->print("py");
-	DOUBLES_EQUAL(0.2,py->probability(config),0.01);
+	DOUBLES_EQUAL(0.8,py->probability(config),0.01);
 
 	// single parent conditional for x
 	vector<double> cpt;
 	cpt += 0.3, 0.6 ; // array index corresponds to binary parent configuration
 	boost::shared_ptr<BinaryConditional> px_y(new BinaryConditional("x","y",cpt));
 	px_y->print("px_y");
-	DOUBLES_EQUAL(0.6,px_y->probability(config),0.01);
+	DOUBLES_EQUAL(0.7,px_y->probability(config),0.01);
 
 	// push back conditionals in topological sort order (parents last)
 	BinaryBayesNet bbn;
@@ -60,7 +72,7 @@ TEST( BinaryBayesNet, constructor )
 	bbn.push_back(px_y);
 
 	// Test probability of 00,01,10,11
-	//DOUBLES_EQUAL(0.56,bbn.probability(config),0.01); // P(y=0)P(x=0|y=0) = 0.8 * 0.7 = 0.56;
+	DOUBLES_EQUAL(0.56,probability(bbn,config),0.01); // P(y=0)P(x=0|y=0) = 0.8 * 0.7 = 0.56;
 }
 
 /* ************************************************************************* */