  Modern applications of strong gravitational lensing require the ability to
use precise and varied observational data to constrain complex lens models. I
discuss two sets of computational methods for lensing calculations. The first
is a new algorithm for solving the lens equation for general mass
distributions. This algorithm makes it possible to apply arbitrarily
complicated models to observed lenses. The second is an evaluation of
techniques for using observational data including positions, fluxes, and time
delays of point-like images, as well as maps of extended images, to constrain
models of strong lenses. The techniques presented here are implemented in a
flexible and user-friendly software package called gravlens, which is made
available to the community.

Astrophysics