title: Find out if/which BLAS library is used by Numpy
body: <p>I use numpy and scipy in different environments (MacOS, Ubuntu, RedHat).
  Usually I install numpy by using the package manager that is available (e.g., mac ports, apt, yum).</p>
  <p>However, if you don't compile Numpy manually, how can you be sure that it uses a BLAS library? Using mac ports, ATLAS is installed as a dependency. However, I am not sure if it is really used. When I perform a simple benchmark, the <code>numpy.dot()</code> function requires approx. 2 times the time than a dot product that is computed using the Eigen C++ library. I am not sure if this is a reasonable result.</p>