  Sampling equilateral closed polygons is of interest in the statistical study
of ring polymers. Over the past 30 years, previous authors have proposed a
variety of simple Markov chain algorithms (but have not been able to show that
they converge to the correct probability distribution) and complicated direct
samplers (which require extended-precision arithmetic to evaluate numerically
unstable polynomials). We present a simple direct sampler which is fast and
numerically stable, and analyze its runtime using a new formula for the volume
of equilateral polygon space as a Dirichlet-type integral.
