diff --git a/gtsam_unstable/linear/QP.h b/gtsam_unstable/linear/QP.h
index 111ab506f..f1324e4d0 100644
--- a/gtsam_unstable/linear/QP.h
+++ b/gtsam_unstable/linear/QP.h
@@ -9,11 +9,11 @@
 
  * -------------------------------------------------------------------------- */
 
-/*
- * QP.h
+/**
+ * @file: QP.h
  * @brief: Factor graphs of a Quadratic Programming problem
  * @date: Dec 8, 2014
- * @author: thduynguyen
+ * @author: Duy-Nguyen Ta
  */
 
 #pragma once
@@ -25,12 +25,12 @@
 namespace gtsam {
 
 /**
- * struct contains factor graphs of a Quadratic Programming problem
+ * Struct contains factor graphs of a Quadratic Programming problem
  */
 struct QP {
   GaussianFactorGraph cost; //!< Quadratic cost factors
-  LinearEqualityFactorGraph equalities; //!< linear equality constraints
-  LinearInequalityFactorGraph inequalities; //!< linear inequality constraints
+  LinearEqualityFactorGraph equalities; //!< linear equality constraints: f(x) = 0
+  LinearInequalityFactorGraph inequalities; //!< linear inequality constraints: g(x) <= 0
 
   /** default constructor */
   QP() :
diff --git a/gtsam_unstable/linear/QPSolver.cpp b/gtsam_unstable/linear/QPSolver.cpp
index 83984adc2..b7ff3780a 100644
--- a/gtsam_unstable/linear/QPSolver.cpp
+++ b/gtsam_unstable/linear/QPSolver.cpp
@@ -1,8 +1,19 @@
-/*
- * QPSolver.cpp
+/* ----------------------------------------------------------------------------
+
+ * GTSAM Copyright 2010, Georgia Tech Research Corporation,
+ * Atlanta, Georgia 30332-0415
+ * All Rights Reserved
+ * Authors: Frank Dellaert, et al. (see THANKS for the full author list)
+
+ * See LICENSE for the license information
+
+ * -------------------------------------------------------------------------- */
+
+/**
+ * @file: QPSolver.cpp
  * @brief:
  * @date: Apr 15, 2014
- * @author: thduynguyen
+ * @author: Duy-Nguyen Ta
  */
 
 #include <gtsam/inference/Symbol.h>
@@ -231,8 +242,8 @@ LinearInequalityFactorGraph QPSolver::identifyActiveConstraints(
         workingFactor->inactivate();
       } else {
         double error = workingFactor->error(initialValues);
-        // TODO: This version of QPSolver doesn't handle infeasible initial point
-        // since we haven't had an LPSolver yet
+        // TODO: find a feasible initial point for QPSolver.
+        // For now, we just throw an exception, since we don't have an LPSolver to do this yet
         if (error > 0)
           throw InfeasibleInitialValues();
 
diff --git a/gtsam_unstable/linear/QPSolver.h b/gtsam_unstable/linear/QPSolver.h
index 1c4cd1f15..b354dcccb 100644
--- a/gtsam_unstable/linear/QPSolver.h
+++ b/gtsam_unstable/linear/QPSolver.h
@@ -8,11 +8,12 @@
  * See LICENSE for the license information
 
  * -------------------------------------------------------------------------- */
-/*
- * QPSolver.h
+
+/**
+ * @file: QPSolver.h
  * @brief: A quadratic programming solver implements the active set method
  * @date: Apr 15, 2014
- * @author: thduynguyen
+ * @author: Duy-Nguyen Ta
  */
 
 #pragma once
@@ -47,19 +48,19 @@ struct QPState {
 };
 
 /**
- * This class implements the active set method to solve quadratic programming problems
- * encoded in a GaussianFactorGraph with special mixed constrained noise models, in which
- * a negative sigma denotes an inequality <=0 constraint,
- * a zero sigma denotes an equality =0 constraint,
- * and a positive sigma denotes a normal Gaussian noise model.
+ * This QPSolver uses the active set method to solve a quadratic programming problem
+ * defined in the QP struct.
+ * Note: This version of QPSolver only works with a feasible initial value.
  */
 class QPSolver {
 
   const QP& qp_; //!< factor graphs of the QP problem, can't be modified!
-  GaussianFactorGraph baseGraph_; //!< factor graphs of cost factors and linear equalities. The working set of inequalities will be added to this base graph in the process.
+  GaussianFactorGraph baseGraph_; //!< factor graphs of cost factors and linear equalities.
+                                  //!< used to initialize the working set factor graph,
+                                  //!< to which active inequalities will be added
   VariableIndex costVariableIndex_, equalityVariableIndex_,
-      inequalityVariableIndex_;
-  FastSet<Key> constrainedKeys_; //!< all constrained keys, will become factors in the dual graph
+      inequalityVariableIndex_;  //!< index to corresponding factors to build dual graphs
+  FastSet<Key> constrainedKeys_; //!< all constrained keys, will become factors in dual graphs
 
 public:
   /// Constructor
@@ -79,13 +80,13 @@ public:
       const VariableIndex& variableIndex) const {
     std::vector<std::pair<Key, Matrix> > Aterms;
     if (variableIndex.find(key) != variableIndex.end()) {
-      BOOST_FOREACH(size_t factorIx, variableIndex[key]){
-      typename FACTOR::shared_ptr factor = graph.at(factorIx);
-      if (!factor->active()) continue;
-      Matrix Ai = factor->getA(factor->find(key)).transpose();
-      Aterms.push_back(std::make_pair(factor->dualKey(), Ai));
+      BOOST_FOREACH(size_t factorIx, variableIndex[key]) {
+        typename FACTOR::shared_ptr factor = graph.at(factorIx);
+        if (!factor->active()) continue;
+        Matrix Ai = factor->getA(factor->find(key)).transpose();
+        Aterms.push_back(std::make_pair(factor->dualKey(), Ai));
+      }
     }
-  }
     return Aterms;
   }
 
@@ -189,7 +190,7 @@ public:
 
   /** Optimize with a provided initial values
    * For this version, it is the responsibility of the caller to provide
-   * a feasible initial value.
+   * a feasible initial value, otherwise, an exception will be thrown.
    * @return a pair of <primal, dual> solutions
    */
   std::pair<VectorValues, VectorValues> optimize(