title: Set random seed in Eigen
body: <p>I am currently filling a vector with random numbers using <code>Eigen::VectorXd::Random(n)</code>.</p>
  <p>Is it possible to seed Eigen's random number generator for deterministic results? Or alternatively, pass a random number generator to Eigen? I found no mention of either in the Eigen wiki, but it seems odd that such a feature would be missing.</p>