72 lines
2.4 KiB
Python
72 lines
2.4 KiB
Python
# TCFG: Tangential Damping Classifier-free Guidance - (arXiv: https://arxiv.org/abs/2503.18137)
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import torch
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from comfy.comfy_types import IO, ComfyNodeABC, InputTypeDict
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def score_tangential_damping(cond_score: torch.Tensor, uncond_score: torch.Tensor) -> torch.Tensor:
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"""Drop tangential components from uncond score to align with cond score."""
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# (B, 1, ...)
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batch_num = cond_score.shape[0]
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cond_score_flat = cond_score.reshape(batch_num, 1, -1).float()
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uncond_score_flat = uncond_score.reshape(batch_num, 1, -1).float()
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# Score matrix A (B, 2, ...)
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score_matrix = torch.cat((uncond_score_flat, cond_score_flat), dim=1)
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try:
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_, _, Vh = torch.linalg.svd(score_matrix, full_matrices=False)
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except RuntimeError:
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# Fallback to CPU
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_, _, Vh = torch.linalg.svd(score_matrix.cpu(), full_matrices=False)
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# Drop the tangential components
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v1 = Vh[:, 0:1, :].to(uncond_score_flat.device) # (B, 1, ...)
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uncond_score_td = (uncond_score_flat @ v1.transpose(-2, -1)) * v1
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return uncond_score_td.reshape_as(uncond_score).to(uncond_score.dtype)
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class TCFG(ComfyNodeABC):
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@classmethod
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def INPUT_TYPES(cls) -> InputTypeDict:
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return {
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"required": {
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"model": (IO.MODEL, {}),
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}
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}
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RETURN_TYPES = (IO.MODEL,)
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RETURN_NAMES = ("patched_model",)
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FUNCTION = "patch"
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CATEGORY = "advanced/guidance"
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DESCRIPTION = "TCFG – Tangential Damping CFG (2503.18137)\n\nRefine the uncond (negative) to align with the cond (positive) for improving quality."
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def patch(self, model):
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m = model.clone()
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def tangential_damping_cfg(args):
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# Assume [cond, uncond, ...]
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x = args["input"]
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conds_out = args["conds_out"]
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if len(conds_out) <= 1 or None in args["conds"][:2]:
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# Skip when either cond or uncond is None
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return conds_out
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cond_pred = conds_out[0]
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uncond_pred = conds_out[1]
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uncond_td = score_tangential_damping(x - cond_pred, x - uncond_pred)
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uncond_pred_td = x - uncond_td
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return [cond_pred, uncond_pred_td] + conds_out[2:]
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m.set_model_sampler_pre_cfg_function(tangential_damping_cfg)
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return (m,)
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NODE_CLASS_MAPPINGS = {
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"TCFG": TCFG,
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}
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NODE_DISPLAY_NAME_MAPPINGS = {
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"TCFG": "Tangential Damping CFG",
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}
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