Feat: SamplerTaylorFlow sampler & SamplerWrapperCFGPP wrapper

This commit is contained in:
Clybius
2026-06-26 10:17:15 -05:00
parent e4f63aa195
commit 45021757c0
2 changed files with 562 additions and 2 deletions
+4
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@@ -8,6 +8,8 @@ clyb_Samplers.add_samplers()
NODE_CLASS_MAPPINGS = {
"ClybGuidance": clyb_Guidance.ClybGuidance,
"SamplerClyb_BDF": clyb_Samplers.SamplerClyb_BDF,
"SamplerTaylorFlow": clyb_Samplers.SamplerTaylorFlow,
"SamplerWrapperCFGPP": clyb_Samplers.SamplerWrapperCFGPP,
"InverseSquaredScheduler": clyb_Schedulers.InverseSquaredScheduler,
"PrintSigmas": clyb_Schedulers.PrintSigmas,
}
@@ -15,6 +17,8 @@ NODE_CLASS_MAPPINGS = {
NODE_DISPLAY_NAME_MAPPINGS = {
"ClybGuidance": "ClybGuidance",
"SamplerClyb_BDF": "SamplerClyb_BDF",
"SamplerTaylorFlow": "SamplerTaylorFlow",
"SamplerWrapperCFGPP": "SamplerWrapperCFGPP",
"InverseSquaredScheduler": "InverseSquaredScheduler",
"PrintSigmas": "PrintSigmas",
}
+558 -2
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@@ -1,9 +1,15 @@
import collections
import math
import torch
from tqdm.auto import trange
from comfy.k_diffusion.sampling import default_noise_sampler
import comfy.model_patcher
from comfy.k_diffusion.sampling import (
default_noise_sampler,
get_ancestral_step,
sigma_to_half_log_snr,
)
import comfy.samplers
@torch.no_grad()
@@ -78,11 +84,421 @@ def sample_clyb_bdf(model, x, sigmas, extra_args=None, callback=None, disable=No
flow = True
return sampler_clyb_bdf(model, x, sigmas, extra_args=extra_args, callback=callback, disable=disable, scalar=scalar, eta=eta, s_noise=s_noise, noise_sampler=noise_sampler, flow=flow)
# =============================================================================
# TAYLOR FLOW SAMPLER - Multi-step sampler using Taylor expansion on
# previous denoised predictions to approximate higher-order derivatives.
# Based on "Leveraging Previous Steps" (Nov 2024).
# =============================================================================
def _construct_vandermonde_flow(history, sigma_ref, max_order, device, dtype):
"""
Build Vandermonde matrix R_p for polynomial interpolation.
R_p[m, i] = (sigma_{n-1-m} - sigma_ref)^i
Args:
history: list of (sigma, denoised) tuples (oldest to newest)
sigma_ref: reference sigma (current timestep t_{n-1})
max_order: maximum polynomial degree (number of previous steps to use)
device: torch device
dtype: torch dtype (float64 for numerical stability)
Returns:
R: (k, k) Vandermonde matrix where k = min(len(history), max_order)
"""
k = min(len(history), max_order)
# Use most recent k points from history
recent_history = list(history)[-k:]
# Build matrix: R[m, i] = (sigma_m - sigma_ref)^i
R = torch.zeros((k, k), device=device, dtype=dtype)
for m, (sigma_m, _) in enumerate(reversed(recent_history)):
h_m = sigma_m - sigma_ref # Time difference (negative for past points)
for i in range(k):
R[m, i] = h_m**i
return R
def _solve_flow_coefficients(R, h_n, method="equilibration", diag_weight=1.0):
"""
Solve for B coefficients using either two-sided equilibration or diagonal-dominant regularization.
Args:
R: Vandermonde matrix (k, k)
h_n: step size (sigma_next - sigma_cur)
method: "equilibration" (default) or "diagonal"
diag_weight: Weight for diagonal component (0.0 to 1.0, default 1.0 for original behavior)
Returns:
B: coefficient vector (k,)
"""
k = R.shape[0]
device = R.device
dtype = R.dtype
# Handle edge cases
if k == 0:
return torch.tensor([], device=device, dtype=dtype)
if k == 1:
# Simple case: just use the diagonal element
return torch.tensor([h_n], device=device, dtype=dtype)
# Compute C vector: C_i = h_n^{i+1} / (i+1)
C = torch.zeros(k, device=device, dtype=dtype)
for i in range(k):
C[i] = (h_n ** (i + 1)) / (i + 1)
if method == "equilibration":
# Iteratively balance row and column norms to equilibrate the matrix
D = torch.eye(k, device=device, dtype=dtype)
E = torch.eye(k, device=device, dtype=dtype)
R_work = R.clone()
for _ in range(5): # 5 iterations typically sufficient for convergence
# Row scaling: normalize rows to unit infinity-norm
row_norms = torch.norm(R_work, dim=1, p=float('inf'))
D_scale = torch.diag(1.0 / torch.sqrt(row_norms + 1e-10))
R_work = D_scale @ R_work
D = D_scale @ D
# Column scaling: normalize columns to unit infinity-norm
col_norms = torch.norm(R_work, dim=0, p=float('inf'))
E_scale = torch.diag(1.0 / torch.sqrt(col_norms + 1e-10))
R_work = R_work @ E_scale
E = E @ E_scale
# Apply row scaling to C
C_eq = D @ C
# Minimal Tikhonov regularization on equilibrated system
lambda_reg = 0.0001
R_reg = R_work + lambda_reg * torch.eye(k, device=device, dtype=dtype)
# Solve and unscale
try:
B_eq = torch.linalg.solve(R_reg, C_eq)
B = E @ B_eq
except torch.linalg.LinAlgError:
B_eq = torch.linalg.lstsq(R_reg, C_eq, rcond=1e-10).solution
B = E @ B_eq
elif method == "diagonal":
# Diagonal-Dominant Extraction
R_diag = torch.diag(torch.diag(R))
R_weighted = diag_weight * R_diag + (1.0 - diag_weight) * R
lambda_reg = 1e-16
R_reg = R_weighted # + lambda_reg * torch.eye(k, device=device, dtype=dtype)
try:
B = torch.linalg.solve(R_reg, C)
except torch.linalg.LinAlgError:
B = torch.linalg.lstsq(R_reg, C, rcond=1e-10).solution
else:
# Unknown method: fallback to equilibration
return _solve_flow_coefficients(R, h_n, method="equilibration", diag_weight=diag_weight)
return B
@torch.no_grad()
def sampler_taylor_flow(
model,
x,
sigmas,
extra_args=None,
callback=None,
disable=None,
order=8,
eta=1.0,
s_noise=1.0,
noise_sampler=None,
flow=False,
sigma_calc="clyb",
):
"""
Taylor Flow sampler - Multi-step sampler using Taylor expansion on previous
denoised predictions to approximate higher-order derivatives.
Based on "Leveraging Previous Steps: A Training-free Fast Solver for
Flow Diffusion" (Nov 2024). Achieves O(h^p) approximation error with only
1 function evaluation per step by reusing cached historical predictions.
Args:
model: Diffusion model
x: Initial latent
sigmas: Sigma schedule
extra_args: Extra arguments for model
callback: Progress callback
disable: Disable progress bar
order: Taylor expansion order (1-16). Higher = more accurate but uses more history
eta: Ancestral sampling eta (stochasticity)
s_noise: Noise scale
noise_sampler: Noise sampler function
flow: Whether using flow-based model (FLUX, SD3, Chroma)
sigma_calc: Ancestral sigma calculation method ("clyb", "taylor-expansion", "ancestral", "adaptive")
Returns:
Denoised latent tensor
"""
extra_args = {} if extra_args is None else extra_args
seed = extra_args.get("seed", None)
noise_sampler = (
default_noise_sampler(x, seed=seed) if noise_sampler is None else noise_sampler
)
s_in = x.new_ones([x.shape[0]])
device = x.device
if len(sigmas) <= 1:
return x
# Rolling history buffer for (sigma, denoised) pairs
history = collections.deque(maxlen=order)
for i in trange(len(sigmas) - 1, disable=disable):
sigma_cur, sigma_next = sigmas[i], sigmas[i + 1]
h_n = sigma_next - sigma_cur # Step size
# Ancestral sigma calculation - selectable method
if sigma_calc == "clyb":
# Original Clyb implementation (logarithmic scaling)
sigma_down = (
sigma_next**2 / (1 + math.log(1.0 + abs(sigma_next - sigma_cur)) * eta)
) ** 0.5
sigma_up = (sigma_next**2 - sigma_down**2) ** 0.5
elif sigma_calc == "taylor-expansion":
# Taylor-Expansion-Matched: exponential integral with quadratic correction
step_ratio = abs(h_n) / max(sigma_next, 1e-8)
taylor_factor = math.exp(-eta * step_ratio)
quadratic_correction = 1 - eta * 0.5 * step_ratio ** 2
sigma_down = sigma_next * taylor_factor * quadratic_correction
sigma_up = sigma_next * max(0.0, 1 - taylor_factor**2) ** 0.5
elif sigma_calc == "ancestral":
# Standard k-diffusion ancestral step
sigma_down, sigma_up = get_ancestral_step(sigma_cur, sigma_next, eta)
elif sigma_calc == "adaptive":
window_size = min(order, len(history))
if window_size >= 2:
history_list = list(history)
recent = history_list[-window_size:]
denoised_list = [d.float() for _, d in recent]
stacked = torch.stack(denoised_list)
mean_d = stacked.mean(dim=0)
var_val = ((stacked - mean_d) ** 2).mean().item()
norm_val = mean_d.pow(2).mean().item()
eps = 1e-8
if math.isfinite(var_val) and math.isfinite(norm_val):
normalized_metric = var_val / (var_val + abs(norm_val) + eps)
normalized_metric = min(1.0, max(0.0, normalized_metric))
else:
normalized_metric = 0.0
sigma_down = sigma_next * (1.0 - eta * normalized_metric)
sigma_down = max(0.0, min(sigma_next, sigma_down))
sigma_up = math.sqrt(max(0.0, sigma_next**2 - sigma_down**2))
else:
sigma_down = (
sigma_next**2 / (1 + math.log(1.0 + abs(sigma_next - sigma_cur)) * eta)
) ** 0.5
sigma_up = (sigma_next**2 - sigma_down**2) ** 0.5
else:
# Default to clyb if unknown method
sigma_down = (
sigma_next**2 / (1 + math.log(1.0 + abs(sigma_next - sigma_cur)) * eta)
) ** 0.5
sigma_up = (sigma_next**2 - sigma_down**2) ** 0.5
# Flow model coefficients
alpha_ip1 = None
alpha_down = None
renoise_coeff = None
alpha_ratio = 1.0
if flow:
alpha_ip1 = 1 - sigma_next
alpha_down = 1 - sigma_down
renoise_coeff = (
sigma_next**2 - sigma_down**2 * alpha_ip1**2 / alpha_down**2
) ** 0.5
alpha_ratio = alpha_ip1 / alpha_down if alpha_down != 0 else 1.0
# =========================================================================
# TAYLOR EXPANSION PHASE (main algorithm)
# =========================================================================
# 1. Single model evaluation at current state
denoised_cur = model(x, sigma_cur * s_in, **extra_args)
# 2. Build Vandermonde matrix from historical timesteps
R_p = _construct_vandermonde_flow(
history, sigma_cur, order, device, torch.float64
)
# 3. Solve for B coefficients
B = _solve_flow_coefficients(R_p, h_n)
B = B.to(dtype=x.dtype)
# 4. Compute D_m differences: D_m = v_history[m] - v_current
D_list = []
for _, denoised_prev in reversed(list(history)[-len(B) :]):
D_m = denoised_prev - denoised_cur
D_list.append(D_m)
# 5. Predictor step: x_pred = Euler + sum(B_m * D_m)
w_next = 1.0 - sigma_down / sigma_cur
euler_step = x.lerp(denoised_cur, weight=w_next)
if len(D_list) > 0:
correction = sum(B[m] * D_list[m] for m in range(len(D_list)))
else:
correction = 0
x_next = euler_step + correction
# 6. Update rolling history
history.append((sigma_cur, denoised_cur))
x = x_next
# =========================================================================
# ANCESTRAL NOISE INJECTION
# =========================================================================
if sigma_next > 0 and eta > 0:
noise = noise_sampler(sigma_cur, sigma_next) * s_noise
if flow:
x = alpha_ratio * x + noise * renoise_coeff
else:
x = x + noise * sigma_up
# Callback
if callback is not None:
callback(
{
"x": x,
"i": i,
"sigma": sigma_cur,
"sigma_hat": sigma_cur,
"denoised": denoised_cur,
}
)
return x
@torch.no_grad()
def sample_taylor_flow(
model,
x,
sigmas,
extra_args=None,
callback=None,
disable=None,
order=8,
eta=1.0,
s_noise=1.0,
noise_sampler=None,
sigma_calc="clyb",
):
"""Wrapper with flow model detection."""
flow = False
if isinstance(
model.inner_model.inner_model.model_sampling, comfy.model_sampling.CONST
):
flow = True
return sampler_taylor_flow(
model,
x,
sigmas,
extra_args=extra_args,
callback=callback,
disable=disable,
order=order,
eta=eta,
s_noise=s_noise,
noise_sampler=noise_sampler,
flow=flow,
sigma_calc=sigma_calc,
)
# =============================================================================
# CFG++ SAMPLER WRAPPER - Captures uncond_denoised via post-CFG hook and
# recomputes a CFG++-style denoised using sigma_to_half_log_snr. Wraps any
# inner SAMPLER (KSampler-style).
# =============================================================================
class CFGPPProxyModel:
def __init__(self, model, sigmas):
self.model = model
self.sigmas = sigmas
self.uncond_denoised = None
def __call__(self, x, sigma, **kwargs):
model_options = kwargs.get("model_options", {}).copy()
def post_cfg_function(args):
self.uncond_denoised = args["uncond_denoised"]
return args["denoised"]
kwargs["model_options"] = comfy.model_patcher.set_model_options_post_cfg_function(
model_options, post_cfg_function, disable_cfg1_optimization=True
)
denoised_guided = self.model(x, sigma, **kwargs)
if self.uncond_denoised is None:
return denoised_guided
sigma_val = sigma.flatten()[0].item()
idx = (self.sigmas - sigma_val).abs().argmin().item()
sigma_next_val = float(self.sigmas[idx + 1]) if idx + 1 < len(self.sigmas) else 0.0
if sigma_next_val == 0:
return denoised_guided
model_sampling = self.model.inner_model.model_patcher.get_model_object("model_sampling")
lambda_fn = lambda s: sigma_to_half_log_snr(s, model_sampling)
alpha_s = sigma_val * lambda_fn(torch.tensor(sigma_val)).exp().item()
alpha_t = sigma_next_val * lambda_fn(torch.tensor(sigma_next_val)).exp().item()
denoised_star = (
sigma_val * alpha_t * denoised_guided
- sigma_next_val * alpha_s * self.uncond_denoised
) / (sigma_val - sigma_next_val)
return denoised_star
def __getattr__(self, name):
return getattr(self.model, name)
@torch.no_grad()
def sample_cfgpp(model, x, sigmas, extra_args=None, callback=None, disable=None,
sampler=None):
extra_args = {} if extra_args is None else extra_args
proxy = CFGPPProxyModel(model, sigmas)
return sampler.sampler_function(
proxy, x, sigmas,
extra_args=extra_args,
callback=callback,
disable=disable,
**sampler.extra_options,
)
# The following function adds the samplers during initialization, in __init__.py
def add_samplers():
from comfy.samplers import KSampler, k_diffusion_sampling
if hasattr(KSampler, "DISCARD_PENULTIMATE_SIGMA_SAMPLERS"):
KSampler.DISCARD_PENULTIMATE_SIGMA_SAMPLERS |= discard_penultimate_sigma_samplers
# ---- Top-level samplers: registered into BOTH KSampler.SAMPLERS (dropdown)
# AND k_diffusion_sampling (function lookup) ----
added = 0
for sampler in extra_samplers: #getattr(self, "sample_{}".format(extra_samplers))
if sampler not in KSampler.SAMPLERS:
@@ -97,8 +513,26 @@ def add_samplers():
import importlib
importlib.reload(k_diffusion_sampling)
# ---- Sampler wrappers: registered into k_diffusion_sampling ONLY (function
# lookup). They are NOT added to KSampler.SAMPLERS, so they will NOT appear
# in the standard KSampler node's sampler_name dropdown. They are only
# accessible through their dedicated wrapper node (e.g. SamplerWrapperCFGPP),
# which calls comfy.samplers.ksampler("<name>", {"sampler": inner_sampler}).
# comfy.samplers.ksampler() resolves the function via
# getattr(k_diffusion_sampling, "sample_<name>"), which is what we set here.
for name, func in extra_sampler_wrappers.items():
if not hasattr(k_diffusion_sampling, "sample_{}".format(name)):
setattr(k_diffusion_sampling, "sample_{}".format(name), func)
extra_samplers = {
"clyb_bdf": sample_clyb_bdf,
"taylor_flow": sample_taylor_flow,
}
# Wrappers are NOT in the standard sampler dropdown. They are only reachable
# via dedicated wrapper nodes (e.g. SamplerWrapperCFGPP).
extra_sampler_wrappers = {
"cfgpp": sample_cfgpp,
}
discard_penultimate_sigma_samplers = set(())
@@ -120,4 +554,126 @@ class SamplerClyb_BDF:
def get_sampler(self, scalar, eta, s_noise):
sampler = comfy.samplers.ksampler("clyb_bdf", {"scalar": scalar, "eta": eta, "s_noise": s_noise})
return (sampler, )
return (sampler, )
class SamplerTaylorFlow:
"""
Taylor Flow sampler - Multi-step sampler using Taylor expansion on previous
denoised predictions to approximate higher-order derivatives.
Based on "Leveraging Previous Steps: A Training-free Fast Solver for
Flow Diffusion" (Nov 2024). Achieves O(h^p) approximation error with only
1 function evaluation per step by reusing cached historical predictions.
Key features:
- Leverages previous steps via rolling history buffer
- Polynomial interpolation via Vandermonde matrix
- Compatible with both flow models (FLUX, SD3, Chroma) and diffusion models
- Multiple ancestral sigma calculation methods
Parameters:
- order (1-16): Taylor expansion order. Higher = more accurate but uses more history
- eta: Ancestral sampling stochasticity (0=deterministic, 1=full stochastic)
- s_noise: Noise scaling factor
- sigma_calc: Ancestral sigma calculation method (clyb, taylor-expansion, ancestral, adaptive)
Recommended for:
- High-quality generation with fewer steps
- Flow-based models (FLUX, SD3, Chroma) with ancestral sampling
- Balancing speed (fewer NFEs) and quality (higher-order accuracy)
- Experimenting with different ancestral noise schedules
"""
@classmethod
def INPUT_TYPES(s):
return {
"required": {
"order": (
"INT",
{
"default": 8,
"min": 1,
"max": 16,
"step": 1,
"tooltip": "Taylor expansion order (1-16). Higher = more accurate but uses more history",
},
),
"eta": (
"FLOAT",
{
"default": 1.0,
"min": 0.0,
"max": 1.0,
"step": 0.01,
"tooltip": "Ancestral sampling stochasticity (0=deterministic, 1=full stochastic)",
},
),
"s_noise": (
"FLOAT",
{
"default": 1.0,
"min": 0.0,
"max": 2.0,
"step": 0.01,
"tooltip": "Noise scaling factor",
},
),
"sigma_calc": (
["clyb", "taylor-expansion", "ancestral", "adaptive"],
{
"default": "clyb",
"tooltip": "Ancestral sigma calculation method: clyb (original log-based), taylor-expansion (exponential+quadratic), ancestral (standard k-diffusion), adaptive (history-based convergence-aware)",
},
),
}
}
RETURN_TYPES = ("SAMPLER",)
CATEGORY = "sampling/custom_sampling/samplers"
FUNCTION = "get_sampler"
def get_sampler(self, order, eta, s_noise, sigma_calc):
sampler = comfy.samplers.ksampler(
"taylor_flow",
{
"order": order,
"eta": eta,
"s_noise": s_noise,
"sigma_calc": sigma_calc,
},
)
return (sampler,)
class SamplerWrapperCFGPP:
"""
CFG++ Sampler Wrapper.
Wraps an inner SAMPLER and intercepts its model call via a proxy that
captures the uncond_denoised output through a post-CFG hook, then
recomputes a CFG++-style denoised. Implementation follows the standard
CFG++ paper formulation: the uncond output is taken from a model sampling
at the next sigma, and the final denoised_star is computed as
(sigma * alpha_t * denoised_guided
- sigma_next * alpha_s * uncond_denoised) / (sigma - sigma_next).
"""
@classmethod
def INPUT_TYPES(s):
return {
"required": {
"sampler": ("SAMPLER",),
}
}
RETURN_TYPES = ("SAMPLER",)
CATEGORY = "sampling/custom_sampling/samplers"
FUNCTION = "get_sampler"
def get_sampler(self, sampler):
sampler = comfy.samplers.ksampler(
"cfgpp",
{"sampler": sampler},
)
return (sampler,)