Method __init__

ldm/models/diffusion/dpm_solver/dpm_solver.py:320–344

Construct a DPM-Solver. We support both the noise prediction model ("predicting epsilon") and the data prediction model ("predicting x0"). If `predict_x0` is False, we use the solver for the noise prediction model (DPM-Solver). If `predict_x0` is True, we use the solver for t

(self, model_fn, noise_schedule, predict_x0=False, thresholding=False, max_val=1.)

class DPM_Solver:
    def __init__(self, model_fn, noise_schedule, predict_x0=False, thresholding=False, max_val=1.):
        """Construct a DPM-Solver.
        We support both the noise prediction model ("predicting epsilon") and the data prediction model ("predicting x0").
        If `predict_x0` is False, we use the solver for the noise prediction model (DPM-Solver).
        If `predict_x0` is True, we use the solver for the data prediction model (DPM-Solver++).
            In such case, we further support the "dynamic thresholding" in [1] when `thresholding` is True.
            The "dynamic thresholding" can greatly improve the sample quality for pixel-space DPMs with large guidance scales.
        Args:
            model_fn: A noise prediction model function which accepts the continuous-time input (t in [epsilon, T]):
                ``
                def model_fn(x, t_continuous):
                    return noise
                ``
            noise_schedule: A noise schedule object, such as NoiseScheduleVP.
            predict_x0: A `bool`. If true, use the data prediction model; else, use the noise prediction model.
            thresholding: A `bool`. Valid when `predict_x0` is True. Whether to use the "dynamic thresholding" in [1].
            max_val: A `float`. Valid when both `predict_x0` and `thresholding` are True. The max value for thresholding.

        [1] Chitwan Saharia, William Chan, Saurabh Saxena, Lala Li, Jay Whang, Emily Denton, Seyed Kamyar Seyed Ghasemipour, Burcu Karagol Ayan, S Sara Mahdavi, Rapha Gontijo Lopes, et al. Photorealistic text-to-image diffusion models with deep language understanding. arXiv preprint arXiv:2205.11487, 2022b.
        """
        self.model = model_fn
        self.noise_schedule = noise_schedule
        self.predict_x0 = predict_x0
        self.thresholding = thresholding
        self.max_val = max_val

    def noise_prediction_fn(self, x, t):
        """