From 4c78ce32d4e1fe19c23ad852c01809598bfbbc6f Mon Sep 17 00:00:00 2001
From: Frank Dellaert <dellaert@gmail.com>
Date: Wed, 13 Jun 2012 18:04:33 +0000
Subject: [PATCH] V should be manifold, and then we can just use retract
 instead of advance

---
 gtsam/nonlinear/GradientDescentOptimizer.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/gtsam/nonlinear/GradientDescentOptimizer.h b/gtsam/nonlinear/GradientDescentOptimizer.h
index 6f79b4779..659aff68c 100644
--- a/gtsam/nonlinear/GradientDescentOptimizer.h
+++ b/gtsam/nonlinear/GradientDescentOptimizer.h
@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <gtsam/base/manifold.h>
 #include <gtsam/nonlinear/NonlinearOptimizer.h>
 
 namespace gtsam {
@@ -175,6 +176,8 @@ double lineSearch(const S &system, const V currentValues, const W &gradient) {
 template <class S, class V>
 V conjugateGradient(const S &system, const V &initial, const NonlinearOptimizerParams &params, const bool gradientDescent) {
 
+  GTSAM_CONCEPT_MANIFOLD_TYPE(V);
+
   // check if we're already close enough
   double currentError = system.error(initial);
   if(currentError <= params.errorTol) {