A preformance report of the change.

gistfile1.txt

======================== WITHOUT ======================== 
CPU: Intel Haswell microarchitecture, speed 3600 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 100000
samples  %        image name               symbol name
179563   12.5333  libnvidia-glcore.so.331.113 /usr/lib/nvidia-331/libnvidia-glcore.so.331.113
77814     5.4313  cell-simulation          Entity::getId() const
70720     4.9362  cell-simulation          sf::Shape::updateOutline()
51316     3.5818  cell-simulation          inList(Entity*, std::vector<Entity*, std::allocator<Entity*> >&)
41346     2.8859  cell-simulation          (anonymous namespace)::computeNormal(sf::Vector2<float> const&, sf::Vector2<float> const&)
37680     2.6300  cell-simulation          bool __gnu_cxx::operator!=<Entity**, std::vector<Entity*, std::allocator<Entity*> > >(__gnu_cxx::__normal_iterator<Entity**, std::vector<Entity*, std::allocator<Entity*> > > const&, __gnu_cxx::__normal_iterator<Entity**, std::vector<Entity*, std::allocator<Entity*> > > const&)
37251     2.6001  cell-simulation          HashNode::query(Entity*, std::vector<Entity*, std::allocator<Entity*> >&)
34945     2.4391  cell-simulation          std::vector<sf::Vertex, std::allocator<sf::Vertex> >::size() const
34476     2.4064  libm-2.19.so             cosf


======================== WITH ======================== 

CPU: Intel Haswell microarchitecture, speed 3600 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 100000
samples  %        image name               symbol name
162502   17.2197  libnvidia-glcore.so.331.113 /usr/lib/nvidia-331/libnvidia-glcore.so.331.113
70642     7.4856  cell-simulation          Entity::getId() const
55607     5.8925  cell-simulation          inList(Entity*, std::vector<Entity*, std::allocator<Entity*> >&)
40217     4.2616  cell-simulation          bool __gnu_cxx::operator!=<Entity**, std::vector<Entity*, std::allocator<Entity*> > >(__gnu_cxx::__normal_iterator<Entity**, std::vector<Entity*, std::allocator<Entity*> > > const&, __gnu_cxx::__normal_iterator<Entity**, std::vector<Entity*, std::allocator<Entity*> > > const&)
34555     3.6617  libm-2.19.so             cosf
30149     3.1948  cell-simulation          HashNode::query(Entity*, std::vector<Entity*, std::allocator<Entity*> >&)
29964     3.1752  cell-simulation          sf::Shape::updateTexCoords()
24850     2.6333  cell-simulation          sf::CircleShape::getPoint(unsigned long) const
23183     2.4566  glqPkvhh (deleted)       /tmp/glqPkvhh (deleted)
21576     2.2863  no-vmlinux               /no-vmlinux

427       0.0452  cell-simulation          sf::Shape::updateOutline()