Questions about sampling implementation

[bobchennan]

Hi, thanks for sharing this great work.

I have a question about the sampling implementation. First of all, what is the difference between diffusion_utils_2 and diffusion_utils_2? I think diffusion_utils_2 is only used for cifar unconditional part. But the difference seems to be larger than that.

Another question is about the difference between current implementation and Algorithm 2 in the paper. If I understand correctly, predict_start_from_noise predicts p(x_0|x_t) and then q_posterior predicts x_{t-1} using equation 7 in the paper. This is different compare to algorithm 2, where equation 11 is used. Are those two equivalent? Or which one is better(stable)?

Thanks!

[bobchennan]

For the second question, it is actually the same.