From 86eb29b4c3a18c0d8e7096e507e2e69cce9338c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A5rd=20Skaflestad?= <Bard.Skaflestad@sintef.no>
Date: Tue, 30 Apr 2013 12:48:02 +0200
Subject: [PATCH] variable(): Avoid memory overhead of identity constructor.

---
 AutoDiffVec.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/AutoDiffVec.hpp b/AutoDiffVec.hpp
index 98dc92c19..e3ed01bdd 100644
--- a/AutoDiffVec.hpp
+++ b/AutoDiffVec.hpp
@@ -42,8 +42,10 @@ namespace AutoDiff
         static ForwardVec variable(const V& val)
         {
             ForwardVec ret(val);
+
+            ret.jac_.reserve(Eigen::VectorXi::Constant(val.size(), 1));
             for (typename M::Index row = 0; row < val.size(); ++row) {
-                ret.jac_.insert(row, row) = 1.0;
+                ret.jac_.insert(row, row) = Scalar(1.0);
             }
             ret.jac_.makeCompressed();
             return ret;