Merge pull request #14583 from continue-revolution/conrevo/lcm-sampler

Official LCM Sampler Support

modules/sd_samplers.py

-from modules import sd_samplers_kdiffusion, sd_samplers_timesteps, shared
+from modules import sd_samplers_kdiffusion, sd_samplers_timesteps, sd_samplers_lcm, shared
 
 # imports for functions that previously were here and are used by other modules
 from modules.sd_samplers_common import samples_to_image_grid, sample_to_image  # noqa: F401
@@ -6,6 +6,7 @@ from modules.sd_samplers_common import samples_to_image_grid, sample_to_image  #
 all_samplers = [
     *sd_samplers_kdiffusion.samplers_data_k_diffusion,
     *sd_samplers_timesteps.samplers_data_timesteps,
+    *sd_samplers_lcm.samplers_data_lcm,
 ]
 all_samplers_map = {x.name: x for x in all_samplers}
 

modules/sd_samplers_lcm.py

+import torch
+
+from k_diffusion import utils, sampling
+from k_diffusion.external import DiscreteEpsDDPMDenoiser
+from k_diffusion.sampling import default_noise_sampler, trange
+
+from modules import shared, sd_samplers_cfg_denoiser, sd_samplers_kdiffusion, sd_samplers_common
+
+
+class LCMCompVisDenoiser(DiscreteEpsDDPMDenoiser):
+    def __init__(self, model):
+        timesteps = 1000
+        original_timesteps = 50     # LCM Original Timesteps (default=50, for current version of LCM)
+        self.skip_steps = timesteps // original_timesteps
+
+        alphas_cumprod_valid = torch.zeros((original_timesteps), dtype=torch.float32, device=model.device)
+        for x in range(original_timesteps):
+            alphas_cumprod_valid[original_timesteps - 1 - x] = model.alphas_cumprod[timesteps - 1 - x * self.skip_steps]
+
+        super().__init__(model, alphas_cumprod_valid, quantize=None)
+
+
+    def get_sigmas(self, n=None,):
+        if n is None:
+            return sampling.append_zero(self.sigmas.flip(0))
+
+        start = self.sigma_to_t(self.sigma_max)
+        end = self.sigma_to_t(self.sigma_min)
+
+        t = torch.linspace(start, end, n, device=shared.sd_model.device)
+
+        return sampling.append_zero(self.t_to_sigma(t))
+
+
+    def sigma_to_t(self, sigma, quantize=None):
+        log_sigma = sigma.log()
+        dists = log_sigma - self.log_sigmas[:, None]
+        return dists.abs().argmin(dim=0).view(sigma.shape) * self.skip_steps + (self.skip_steps - 1)
+
+
+    def t_to_sigma(self, timestep):
+        t = torch.clamp(((timestep - (self.skip_steps - 1)) / self.skip_steps).float(), min=0, max=(len(self.sigmas) - 1))
+        return super().t_to_sigma(t)
+
+
+    def get_eps(self, *args, **kwargs):
+        return self.inner_model.apply_model(*args, **kwargs)
+
+
+    def get_scaled_out(self, sigma, output, input):
+        sigma_data = 0.5
+        scaled_timestep = utils.append_dims(self.sigma_to_t(sigma), output.ndim) * 10.0
+
+        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 * output + c_skip * input
+
+
+    def forward(self, input, sigma, **kwargs):
+        c_out, c_in = [utils.append_dims(x, input.ndim) for x in self.get_scalings(sigma)]
+        eps = self.get_eps(input * c_in, self.sigma_to_t(sigma), **kwargs)
+        return self.get_scaled_out(sigma, input + eps * c_out, input)
+
+
+def sample_lcm(model, x, sigmas, extra_args=None, callback=None, disable=None, noise_sampler=None):
+    extra_args = {} if extra_args is None else extra_args
+    noise_sampler = default_noise_sampler(x) if noise_sampler is None else noise_sampler
+    s_in = x.new_ones([x.shape[0]])
+
+    for i in trange(len(sigmas) - 1, disable=disable):
+        denoised = model(x, sigmas[i] * s_in, **extra_args)
+
+        if callback is not None:
+            callback({'x': x, 'i': i, 'sigma': sigmas[i], 'sigma_hat': sigmas[i], 'denoised': denoised})
+
+        x = denoised
+        if sigmas[i + 1] > 0:
+            x += sigmas[i + 1] * noise_sampler(sigmas[i], sigmas[i + 1])
+    return x
+
+
+class CFGDenoiserLCM(sd_samplers_cfg_denoiser.CFGDenoiser):
+    @property
+    def inner_model(self):
+        if self.model_wrap is None:
+            denoiser = LCMCompVisDenoiser
+            self.model_wrap = denoiser(shared.sd_model)
+
+        return self.model_wrap
+
+
+class LCMSampler(sd_samplers_kdiffusion.KDiffusionSampler):
+    def __init__(self, funcname, sd_model, options=None):
+        super().__init__(funcname, sd_model, options)
+        self.model_wrap_cfg = CFGDenoiserLCM(self)
+        self.model_wrap = self.model_wrap_cfg.inner_model
+
+
+samplers_lcm = [('LCM', sample_lcm, ['k_lcm'], {})]
+samplers_data_lcm = [
+    sd_samplers_common.SamplerData(label, lambda model, funcname=funcname: LCMSampler(funcname, model), aliases, options)
+    for label, funcname, aliases, options in samplers_lcm
+]