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71 lines
2.4 KiB
Python
71 lines
2.4 KiB
Python
"""TCFG: Tangential Damping Classifier-free Guidance - (arXiv: https://arxiv.org/abs/2503.18137)"""
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from __future__ import annotations
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import torch
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from comfy_api.v3 import io
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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(io.ComfyNode):
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@classmethod
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def define_schema(cls):
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return io.Schema(
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node_id="TCFG_V3",
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display_name="Tangential Damping CFG _V3",
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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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inputs=[
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io.Model.Input("model"),
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],
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outputs=[
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io.Model.Output(display_name="patched_model"),
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],
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)
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@classmethod
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def execute(cls, 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 io.NodeOutput(m)
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NODES_LIST = [
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TCFG,
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]
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