Adaptive Importance Sampling via Stochastic Convex Programming
  We show that the variance of the Monte Carlo estimator that is importance sampled from an exponential family is a convex function of the natural parameter of the distribution. With this insight, we propose an adaptive importance sampling algorithm that simultaneously improves the choice of sampling distribution while accumulating a Monte Carlo estimate. Exploiting convexity, we prove that the method's unbiased estimator has variance that is asymptotically optimal over the exponential family. 
Ernest K. Ryu and Stephen P. Boyd
stat.ME math.OC stat.CO