From cb37b025e97ed8961d395af09a6fbf6402f9a865 Mon Sep 17 00:00:00 2001
From: thduynguyen <thduynguyen@gmail.com>
Date: Tue, 15 Apr 2014 06:11:26 -0400
Subject: [PATCH] small improvement on negative weights

---
 gtsam/linear/NoiseModel.cpp | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/gtsam/linear/NoiseModel.cpp b/gtsam/linear/NoiseModel.cpp
index 933a40ab2..f98a92ff5 100644
--- a/gtsam/linear/NoiseModel.cpp
+++ b/gtsam/linear/NoiseModel.cpp
@@ -428,15 +428,13 @@ SharedDiagonal Constrained::QR(Matrix& Ab) const {
 
   Vector pseudo(m); // allocate storage for pseudo-inverse
   Vector invsigmas = reciprocal(sigmas_);
-  // Obtain the signs of each elements.
-  // We use negative signs to denote inequality constraints
-  // TODO: might be slow!
-  Vector signs(sigmas_.size());
-  for (size_t s = 0; s<sigmas_.size(); ++s) signs[s] = (sigmas_[s]<0)?-1.0:1.0 ;
   gtsam::print(invsigmas, "invsigmas: ");
   Vector weights = emul(invsigmas,invsigmas); // calculate weights once
-  // We use negative signs to denote inequality constraints
-  weights = emul(weights, signs);
+
+  // Denote weights of inequality constraints with the negative sign
+  // TODO: might be slow!
+  for (size_t s = 0; s<sigmas_.size(); ++s)
+    weights[s] = (sigmas_[s]<0)?-weights[s]:weights[s];
   gtsam::print(weights, "weights: ");
 
   // We loop over all columns, because the columns that can be eliminated