Method __init__

Create a wrapper class for the forward SDE (VP type). *** Update: We support discrete-time diffusion models by implementing a picewise linear interpolation for log_alpha_t. We recommend to use schedule='discrete' for the discrete-time diffusion models, especially for

(
            self,
            schedule='discrete',
            betas=None,
            alphas_cumprod=None,
            continuous_beta_0=0.1,
            continuous_beta_1=20.,
            dtype=torch.float32,
        )