Why do we sample z i , z i+1 , …, z i+l-1 together?
assume that we draw z i , z i+1 , …, z i+l-1 one by one, and it is now time to sample z i+1 according to the conditional probability ( ) Recall step 6-b in the generative TWC model: it says " as this probability is a factorial of the target probability, it follows that ( ) z i+1 should be equal to z i and not change during sampling.