Method q_sample

diffusion/gaussian_diffusion.py:226–244

Diffuse the dataset for a given number of diffusion steps. In other words, sample from q(x_t | x_0). :param x_start: the initial dataset batch. :param t: the number of diffusion steps (minus 1). Here, 0 means one step. :param noise: if specified, the split-

(self, x_start, t, noise=None)

        return mean, variance, log_variance

    def q_sample(self, x_start, t, noise=None):
        """
        Diffuse the dataset for a given number of diffusion steps.

        In other words, sample from q(x_t | x_0).

        :param x_start: the initial dataset batch.
        :param t: the number of diffusion steps (minus 1). Here, 0 means one step.
        :param noise: if specified, the split-out normal noise.
        :return: A noisy version of x_start.
        """
        if noise is None:
            noise = th.randn_like(x_start)
        assert noise.shape == x_start.shape
        return (
            _extract_into_tensor(self.sqrt_alphas_cumprod, t, x_start.shape) * x_start
            + _extract_into_tensor(self.sqrt_one_minus_alphas_cumprod, t, x_start.shape)
            * noise
        )

    def q_posterior_mean_variance(self, x_start, x_t, t):
        """