From 2673e1664ce4a107a27d5c0c5480c0be5eebd6af Mon Sep 17 00:00:00 2001
From: thduynguyen <thduynguyen@gmail.com>
Date: Sat, 13 Dec 2014 01:05:24 -0500
Subject: [PATCH] reapply a bug fix in isConstrained when no model exists

---
 gtsam/linear/JacobianFactor.cpp | 4 ----
 gtsam/linear/JacobianFactor.h   | 4 +++-
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/gtsam/linear/JacobianFactor.cpp b/gtsam/linear/JacobianFactor.cpp
index 2c677dd17..566a98fc2 100644
--- a/gtsam/linear/JacobianFactor.cpp
+++ b/gtsam/linear/JacobianFactor.cpp
@@ -580,10 +580,6 @@ void JacobianFactor::gradientAtZero(double* d) const {
 
 /* ************************************************************************* */
 Vector JacobianFactor::gradient(Key key, const VectorValues& x) const {
-  if (isConstrained()) { // Untested. But see the explanation in gradientAtZero()
-    Matrix A = getA(find(key));
-    return A.transpose()*ones(rows());
-  }
   // TODO: optimize it for JacobianFactor without converting to a HessianFactor
   HessianFactor hessian(*this);
   return hessian.gradient(key, x);
diff --git a/gtsam/linear/JacobianFactor.h b/gtsam/linear/JacobianFactor.h
index 71f3febbf..d33c5e07c 100644
--- a/gtsam/linear/JacobianFactor.h
+++ b/gtsam/linear/JacobianFactor.h
@@ -230,7 +230,9 @@ namespace gtsam {
     virtual bool empty() const { return size() == 0 /*|| rows() == 0*/; }
 
     /** is noise model constrained ? */
-    bool isConstrained() const { return model_->isConstrained(); }
+    bool isConstrained() const {
+      return model_ && model_->isConstrained();
+    }
 
     /** Return the dimension of the variable pointed to by the given key iterator
      * todo: Remove this in favor of keeping track of dimensions with variables?