ComfyUI/comfy_extras/nodes_model_advanced.py

import folder_paths
import comfy.sd
import comfy.model_sampling
import torch

class LCM(comfy.model_sampling.EPS):
    def calculate_denoised(self, sigma, model_output, model_input):
        timestep = self.timestep(sigma).view(sigma.shape[:1] + (1,) * (model_output.ndim - 1))
        sigma = sigma.view(sigma.shape[:1] + (1,) * (model_output.ndim - 1))
        x0 = model_input - model_output * sigma

        sigma_data = 0.5
        scaled_timestep = timestep * 10.0 #timestep_scaling

        c_skip = sigma_data**2 / (scaled_timestep**2 + sigma_data**2)
        c_out = scaled_timestep / (scaled_timestep**2 + sigma_data**2) ** 0.5

        return c_out * x0 + c_skip * model_input

class ModelSamplingDiscreteLCM(torch.nn.Module):
    def __init__(self):
        super().__init__()
        self.sigma_data = 1.0
        timesteps = 1000
        beta_start = 0.00085
        beta_end = 0.012

        betas = torch.linspace(beta_start**0.5, beta_end**0.5, timesteps, dtype=torch.float32) ** 2
        alphas = 1.0 - betas
        alphas_cumprod = torch.cumprod(alphas, dim=0)

        original_timesteps = 50
        self.skip_steps = timesteps // original_timesteps


        alphas_cumprod_valid = torch.zeros((original_timesteps), dtype=torch.float32)
        for x in range(original_timesteps):
            alphas_cumprod_valid[original_timesteps - 1 - x] = alphas_cumprod[timesteps - 1 - x * self.skip_steps]

        sigmas = ((1 - alphas_cumprod_valid) / alphas_cumprod_valid) ** 0.5
        self.set_sigmas(sigmas)

    def set_sigmas(self, sigmas):
        self.register_buffer('sigmas', sigmas)
        self.register_buffer('log_sigmas', sigmas.log())

    @property
    def sigma_min(self):
        return self.sigmas[0]

    @property
    def sigma_max(self):
        return self.sigmas[-1]

    def timestep(self, sigma):
        log_sigma = sigma.log()
        dists = log_sigma.to(self.log_sigmas.device) - self.log_sigmas[:, None]
        return dists.abs().argmin(dim=0).view(sigma.shape) * self.skip_steps + (self.skip_steps - 1)

    def sigma(self, timestep):
        t = torch.clamp(((timestep - (self.skip_steps - 1)) / self.skip_steps).float(), min=0, max=(len(self.sigmas) - 1))
        low_idx = t.floor().long()
        high_idx = t.ceil().long()
        w = t.frac()
        log_sigma = (1 - w) * self.log_sigmas[low_idx] + w * self.log_sigmas[high_idx]
        return log_sigma.exp()

    def percent_to_sigma(self, percent):
        return self.sigma(torch.tensor(percent * 999.0))


def rescale_zero_terminal_snr_sigmas(sigmas):
    alphas_cumprod = 1 / ((sigmas * sigmas) + 1)
    alphas_bar_sqrt = alphas_cumprod.sqrt()

    # Store old values.
    alphas_bar_sqrt_0 = alphas_bar_sqrt[0].clone()
    alphas_bar_sqrt_T = alphas_bar_sqrt[-1].clone()

    # Shift so the last timestep is zero.
    alphas_bar_sqrt -= (alphas_bar_sqrt_T)

    # Scale so the first timestep is back to the old value.
    alphas_bar_sqrt *= alphas_bar_sqrt_0 / (alphas_bar_sqrt_0 - alphas_bar_sqrt_T)

    # Convert alphas_bar_sqrt to betas
    alphas_bar = alphas_bar_sqrt**2  # Revert sqrt
    alphas_bar[-1] = 4.8973451890853435e-08
    return ((1 - alphas_bar) / alphas_bar) ** 0.5

class ModelSamplingDiscrete:
    @classmethod
    def INPUT_TYPES(s):
        return {"required": { "model": ("MODEL",),
                              "sampling": (["eps", "v_prediction", "lcm"],),
                              "zsnr": ("BOOLEAN", {"default": False}),
                              }}

    RETURN_TYPES = ("MODEL",)
    FUNCTION = "patch"

    CATEGORY = "advanced/model"

    def patch(self, model, sampling, zsnr):
        m = model.clone()

        sampling_base = comfy.model_sampling.ModelSamplingDiscrete
        if sampling == "eps":
            sampling_type = comfy.model_sampling.EPS
        elif sampling == "v_prediction":
            sampling_type = comfy.model_sampling.V_PREDICTION
        elif sampling == "lcm":
            sampling_type = LCM
            sampling_base = ModelSamplingDiscreteLCM

        class ModelSamplingAdvanced(sampling_base, sampling_type):
            pass

        model_sampling = ModelSamplingAdvanced()
        if zsnr:
            model_sampling.set_sigmas(rescale_zero_terminal_snr_sigmas(model_sampling.sigmas))

        m.add_object_patch("model_sampling", model_sampling)
        return (m, )

NODE_CLASS_MAPPINGS = {
    "ModelSamplingDiscrete": ModelSamplingDiscrete,
}