we are not able to recover exactly the distribution that was used to generate the data in practice we observe that variational autoencoders are very good at obtaining high likelihood but they tend to produce lower quality samples and in particular the samples are often relatively blurry another major family of models is the Bolton machine these also have an explicit density function that is not actually tractable in this case the Bolton machine is defined by an energy function and the probability of a particular state is proportional to e to