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""" | |
Partially ported from https://github.com/crowsonkb/k-diffusion/blob/master/k_diffusion/sampling.py | |
""" | |
from typing import Dict, Union | |
import torch | |
from omegaconf import ListConfig, OmegaConf | |
from tqdm import tqdm | |
from ...modules.diffusionmodules.sampling_utils import (get_ancestral_step, | |
linear_multistep_coeff, | |
to_d, to_neg_log_sigma, | |
to_sigma) | |
from ...util import append_dims, default, instantiate_from_config | |
DEFAULT_GUIDER = {"target": "sgm.modules.diffusionmodules.guiders.IdentityGuider"} | |
class BaseDiffusionSampler: | |
def __init__( | |
self, | |
discretization_config: Union[Dict, ListConfig, OmegaConf], | |
num_steps: Union[int, None] = None, | |
guider_config: Union[Dict, ListConfig, OmegaConf, None] = None, | |
verbose: bool = False, | |
device: str = "cuda", | |
): | |
self.num_steps = num_steps | |
self.discretization = instantiate_from_config(discretization_config) | |
self.guider = instantiate_from_config( | |
default( | |
guider_config, | |
DEFAULT_GUIDER, | |
) | |
) | |
self.verbose = verbose | |
self.device = device | |
def prepare_sampling_loop(self, x, cond, uc=None, num_steps=None): | |
sigmas = self.discretization( | |
self.num_steps if num_steps is None else num_steps, device=self.device | |
) | |
uc = default(uc, cond) | |
x *= torch.sqrt(1.0 + sigmas[0] ** 2.0) | |
num_sigmas = len(sigmas) | |
s_in = x.new_ones([x.shape[0]]) | |
return x, s_in, sigmas, num_sigmas, cond, uc | |
def denoise(self, x, denoiser, sigma, cond, uc): | |
denoised = denoiser(*self.guider.prepare_inputs(x, sigma, cond, uc)) | |
denoised = self.guider(denoised, sigma) | |
return denoised | |
def get_sigma_gen(self, num_sigmas): | |
sigma_generator = range(num_sigmas - 1) | |
if self.verbose: | |
print("#" * 30, " Sampling setting ", "#" * 30) | |
print(f"Sampler: {self.__class__.__name__}") | |
print(f"Discretization: {self.discretization.__class__.__name__}") | |
print(f"Guider: {self.guider.__class__.__name__}") | |
sigma_generator = tqdm( | |
sigma_generator, | |
total=num_sigmas, | |
desc=f"Sampling with {self.__class__.__name__} for {num_sigmas} steps", | |
) | |
return sigma_generator | |
class SingleStepDiffusionSampler(BaseDiffusionSampler): | |
def sampler_step(self, sigma, next_sigma, denoiser, x, cond, uc, *args, **kwargs): | |
raise NotImplementedError | |
def euler_step(self, x, d, dt): | |
return x + dt * d | |
class EDMSampler(SingleStepDiffusionSampler): | |
def __init__( | |
self, s_churn=0.0, s_tmin=0.0, s_tmax=float("inf"), s_noise=1.0, *args, **kwargs | |
): | |
super().__init__(*args, **kwargs) | |
self.s_churn = s_churn | |
self.s_tmin = s_tmin | |
self.s_tmax = s_tmax | |
self.s_noise = s_noise | |
def sampler_step(self, sigma, next_sigma, denoiser, x, cond, uc=None, gamma=0.0): | |
sigma_hat = sigma * (gamma + 1.0) | |
if gamma > 0: | |
eps = torch.randn_like(x) * self.s_noise | |
x = x + eps * append_dims(sigma_hat**2 - sigma**2, x.ndim) ** 0.5 | |
denoised = self.denoise(x, denoiser, sigma_hat, cond, uc) | |
d = to_d(x, sigma_hat, denoised) | |
dt = append_dims(next_sigma - sigma_hat, x.ndim) | |
euler_step = self.euler_step(x, d, dt) | |
x = self.possible_correction_step( | |
euler_step, x, d, dt, next_sigma, denoiser, cond, uc | |
) | |
return x | |
def __call__(self, denoiser, x, cond, uc=None, num_steps=None): | |
x, s_in, sigmas, num_sigmas, cond, uc = self.prepare_sampling_loop( | |
x, cond, uc, num_steps | |
) | |
for i in self.get_sigma_gen(num_sigmas): | |
gamma = ( | |
min(self.s_churn / (num_sigmas - 1), 2**0.5 - 1) | |
if self.s_tmin <= sigmas[i] <= self.s_tmax | |
else 0.0 | |
) | |
x = self.sampler_step( | |
s_in * sigmas[i], | |
s_in * sigmas[i + 1], | |
denoiser, | |
x, | |
cond, | |
uc, | |
gamma, | |
) | |
return x | |
class AncestralSampler(SingleStepDiffusionSampler): | |
def __init__(self, eta=1.0, s_noise=1.0, *args, **kwargs): | |
super().__init__(*args, **kwargs) | |
self.eta = eta | |
self.s_noise = s_noise | |
self.noise_sampler = lambda x: torch.randn_like(x) | |
def ancestral_euler_step(self, x, denoised, sigma, sigma_down): | |
d = to_d(x, sigma, denoised) | |
dt = append_dims(sigma_down - sigma, x.ndim) | |
return self.euler_step(x, d, dt) | |
def ancestral_step(self, x, sigma, next_sigma, sigma_up): | |
x = torch.where( | |
append_dims(next_sigma, x.ndim) > 0.0, | |
x + self.noise_sampler(x) * self.s_noise * append_dims(sigma_up, x.ndim), | |
x, | |
) | |
return x | |
def __call__(self, denoiser, x, cond, uc=None, num_steps=None): | |
x, s_in, sigmas, num_sigmas, cond, uc = self.prepare_sampling_loop( | |
x, cond, uc, num_steps | |
) | |
for i in self.get_sigma_gen(num_sigmas): | |
x = self.sampler_step( | |
s_in * sigmas[i], | |
s_in * sigmas[i + 1], | |
denoiser, | |
x, | |
cond, | |
uc, | |
) | |
return x | |
class LinearMultistepSampler(BaseDiffusionSampler): | |
def __init__( | |
self, | |
order=4, | |
*args, | |
**kwargs, | |
): | |
super().__init__(*args, **kwargs) | |
self.order = order | |
def __call__(self, denoiser, x, cond, uc=None, num_steps=None, **kwargs): | |
x, s_in, sigmas, num_sigmas, cond, uc = self.prepare_sampling_loop( | |
x, cond, uc, num_steps | |
) | |
ds = [] | |
sigmas_cpu = sigmas.detach().cpu().numpy() | |
for i in self.get_sigma_gen(num_sigmas): | |
sigma = s_in * sigmas[i] | |
denoised = denoiser( | |
*self.guider.prepare_inputs(x, sigma, cond, uc), **kwargs | |
) | |
denoised = self.guider(denoised, sigma) | |
d = to_d(x, sigma, denoised) | |
ds.append(d) | |
if len(ds) > self.order: | |
ds.pop(0) | |
cur_order = min(i + 1, self.order) | |
coeffs = [ | |
linear_multistep_coeff(cur_order, sigmas_cpu, i, j) | |
for j in range(cur_order) | |
] | |
x = x + sum(coeff * d for coeff, d in zip(coeffs, reversed(ds))) | |
return x | |
class EulerEDMSampler(EDMSampler): | |
def possible_correction_step( | |
self, euler_step, x, d, dt, next_sigma, denoiser, cond, uc | |
): | |
return euler_step | |
class HeunEDMSampler(EDMSampler): | |
def possible_correction_step( | |
self, euler_step, x, d, dt, next_sigma, denoiser, cond, uc | |
): | |
if torch.sum(next_sigma) < 1e-14: | |
# Save a network evaluation if all noise levels are 0 | |
return euler_step | |
else: | |
denoised = self.denoise(euler_step, denoiser, next_sigma, cond, uc) | |
d_new = to_d(euler_step, next_sigma, denoised) | |
d_prime = (d + d_new) / 2.0 | |
# apply correction if noise level is not 0 | |
x = torch.where( | |
append_dims(next_sigma, x.ndim) > 0.0, x + d_prime * dt, euler_step | |
) | |
return x | |
class EulerAncestralSampler(AncestralSampler): | |
def sampler_step(self, sigma, next_sigma, denoiser, x, cond, uc): | |
sigma_down, sigma_up = get_ancestral_step(sigma, next_sigma, eta=self.eta) | |
denoised = self.denoise(x, denoiser, sigma, cond, uc) | |
x = self.ancestral_euler_step(x, denoised, sigma, sigma_down) | |
x = self.ancestral_step(x, sigma, next_sigma, sigma_up) | |
return x | |
class DPMPP2SAncestralSampler(AncestralSampler): | |
def get_variables(self, sigma, sigma_down): | |
t, t_next = [to_neg_log_sigma(s) for s in (sigma, sigma_down)] | |
h = t_next - t | |
s = t + 0.5 * h | |
return h, s, t, t_next | |
def get_mult(self, h, s, t, t_next): | |
mult1 = to_sigma(s) / to_sigma(t) | |
mult2 = (-0.5 * h).expm1() | |
mult3 = to_sigma(t_next) / to_sigma(t) | |
mult4 = (-h).expm1() | |
return mult1, mult2, mult3, mult4 | |
def sampler_step(self, sigma, next_sigma, denoiser, x, cond, uc=None, **kwargs): | |
sigma_down, sigma_up = get_ancestral_step(sigma, next_sigma, eta=self.eta) | |
denoised = self.denoise(x, denoiser, sigma, cond, uc) | |
x_euler = self.ancestral_euler_step(x, denoised, sigma, sigma_down) | |
if torch.sum(sigma_down) < 1e-14: | |
# Save a network evaluation if all noise levels are 0 | |
x = x_euler | |
else: | |
h, s, t, t_next = self.get_variables(sigma, sigma_down) | |
mult = [ | |
append_dims(mult, x.ndim) for mult in self.get_mult(h, s, t, t_next) | |
] | |
x2 = mult[0] * x - mult[1] * denoised | |
denoised2 = self.denoise(x2, denoiser, to_sigma(s), cond, uc) | |
x_dpmpp2s = mult[2] * x - mult[3] * denoised2 | |
# apply correction if noise level is not 0 | |
x = torch.where(append_dims(sigma_down, x.ndim) > 0.0, x_dpmpp2s, x_euler) | |
x = self.ancestral_step(x, sigma, next_sigma, sigma_up) | |
return x | |
class DPMPP2MSampler(BaseDiffusionSampler): | |
def get_variables(self, sigma, next_sigma, previous_sigma=None): | |
t, t_next = [to_neg_log_sigma(s) for s in (sigma, next_sigma)] | |
h = t_next - t | |
if previous_sigma is not None: | |
h_last = t - to_neg_log_sigma(previous_sigma) | |
r = h_last / h | |
return h, r, t, t_next | |
else: | |
return h, None, t, t_next | |
def get_mult(self, h, r, t, t_next, previous_sigma): | |
mult1 = to_sigma(t_next) / to_sigma(t) | |
mult2 = (-h).expm1() | |
if previous_sigma is not None: | |
mult3 = 1 + 1 / (2 * r) | |
mult4 = 1 / (2 * r) | |
return mult1, mult2, mult3, mult4 | |
else: | |
return mult1, mult2 | |
def sampler_step( | |
self, | |
old_denoised, | |
previous_sigma, | |
sigma, | |
next_sigma, | |
denoiser, | |
x, | |
cond, | |
uc=None, | |
): | |
denoised = self.denoise(x, denoiser, sigma, cond, uc) | |
h, r, t, t_next = self.get_variables(sigma, next_sigma, previous_sigma) | |
mult = [ | |
append_dims(mult, x.ndim) | |
for mult in self.get_mult(h, r, t, t_next, previous_sigma) | |
] | |
x_standard = mult[0] * x - mult[1] * denoised | |
if old_denoised is None or torch.sum(next_sigma) < 1e-14: | |
# Save a network evaluation if all noise levels are 0 or on the first step | |
return x_standard, denoised | |
else: | |
denoised_d = mult[2] * denoised - mult[3] * old_denoised | |
x_advanced = mult[0] * x - mult[1] * denoised_d | |
# apply correction if noise level is not 0 and not first step | |
x = torch.where( | |
append_dims(next_sigma, x.ndim) > 0.0, x_advanced, x_standard | |
) | |
return x, denoised | |
def __call__(self, denoiser, x, cond, uc=None, num_steps=None, **kwargs): | |
x, s_in, sigmas, num_sigmas, cond, uc = self.prepare_sampling_loop( | |
x, cond, uc, num_steps | |
) | |
old_denoised = None | |
for i in self.get_sigma_gen(num_sigmas): | |
x, old_denoised = self.sampler_step( | |
old_denoised, | |
None if i == 0 else s_in * sigmas[i - 1], | |
s_in * sigmas[i], | |
s_in * sigmas[i + 1], | |
denoiser, | |
x, | |
cond, | |
uc=uc, | |
) | |
return x | |