lwtDev::DummySource Node1 lwtDev::DummySource + DummySource() + at() + matrix_at() Node2 lwtDev::ISource + ~ISource() + at() + matrix_at() Node2->Node1 Node3 std::vector< size_t > + elements Node3->Node1 -m_sizes Node4 std::vector< std::pair < size_t, size_t > > + elements Node4->Node1 -m_matrix_sizes