  We present a novel proposal strategy for the Metropolis-Hastings algorithm
designed to efficiently sample general convex polytopes in 100 or more
dimensions. This improves upon previous sampling strategies used for free-form
reconstruction of gravitational lenses, but is general enough to be applied to
other fields. We have written a parallel implementation within the lens
modeling framework GLASS. Testing shows that we are able to produce uniform
uncorrelated random samples which are necessary for exploring the degeneracies
inherent in lens reconstruction.
