DPM++ 2M Alt Sampler for ComfyUIMade the DPM++ 2M Alt Karras Sampler to work with ComfyUI.Comparison: Left DPMPP 2M Karras | Right DPMPP 2M Alt KarrasNote: The face isn't an accurate comparison due to different seed in facedetailer, other parts of the picture is using the same seed.<img src="https://image.civitai.com/xG1nkqKTMzGDvpLrqFT7WA/3cc65c1d-4b7c-4b89-af29-174443f5fc95/width=525/3cc65c1d-4b7c-4b89-af29-174443f5fc95.jpeg" />Credits to hallastore, original thread: <a target="_blank" rel="ugc" href="https://github.com/AUTOMATIC1111/stable-diffusion-webui/discussions/8457">https://github.com/AUTOMATIC1111/stable-diffusion-webui/discussions/8457</a>Instructions:Unzip method:<ol><li>IMPORTANT: Make backup of these two files of just in case new update affects the samplers.For ComfyUI Portable:</li></ol><ul><li>ComfyUI_windows_portable\ComfyUI\comfy\samplers.py</li><li>ComfyUI_windows_portable\ComfyUI\comfy\k_diffusion\sampling.pyFor Automatic 1111:</li><li>Stable-diffusion-webui\extensions\sd-webui-comfyui\ComfyUI\comfy\samplers.py</li><li>Stable-diffusion-webui\extensions\sd-webui-comfyui\ComfyUI\comfy\k_diffusion\sampling.py</li></ul><ol><li>Unpack zip to directory</li></ol><ul><li>For Portable ComfyUI: ComfyUI_windows_portable\ComfyUI\comfy</li><li>For Automatic 1111 ComfyUI extension: Stable-diffusion-webui\extensions\sd-webui-comfyui\ComfyUI\comfy</li></ul><ol><li>Sampler is named dpmpp_2m_alt in ComfyUI</li></ol>Manual Method:<ol><li>IMPORTANT: Make backup of these two files of just in case new update affects the samplers.For ComfyUI Portable:</li></ol><ul><li>ComfyUI_windows_portable\ComfyUI\comfy\samplers.py</li><li>ComfyUI_windows_portable\ComfyUI\comfy\k_diffusion\sampling.pyFor Automatic 1111:</li><li>Stable-diffusion-webui\extensions\sd-webui-comfyui\ComfyUI\comfy\samplers.py</li><li>Stable-diffusion-webui\extensions\sd-webui-comfyui\ComfyUI\comfy\k_diffusion\sampling.pyTips: The following instructions is for ComfyUI Portable but it is the same for Automatic 1111, just navigate to the path given above for the *.py files with the same name.</li></ul><ol><li>Open ComfyUI_windows_portable\ComfyUI\comfy\samplers.pysearch for KSAMPLER_NAMES</li><li><img src="https://image.civitai.com/xG1nkqKTMzGDvpLrqFT7WA/7cee01de-20a5-4461-bf0a-e8819551027a/width=525/7cee01de-20a5-4461-bf0a-e8819551027a.jpeg" /></li><li>Add dpmpp_2m_alt as a new value and save file, make sure you include the comma and quotes.</li><li><img src="https://image.civitai.com/xG1nkqKTMzGDvpLrqFT7WA/c8507780-663b-4f53-9922-5310653374f9/width=525/c8507780-663b-4f53-9922-5310653374f9.jpeg" /></li><li>Open ComfyUI_windows_portable\ComfyUI\comfy\k_diffusion\sampling.py\</li><li>Copy the following code.<pre><code>@torch.no_grad()
def sample_dpmpp_2m_alt(model, x, sigmas, extra_args=None, callback=None, disable=None):
 """DPM-Solver++(2M)."""
 extra_args = {} if extra_args is None else extra_args
 s_in = x.new_ones([x.shape[0]])
 sigma_fn = lambda t: t.neg().exp()
 t_fn = lambda sigma: sigma.log().neg()
 old_denoised = None

 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})
 t, t_next = t_fn(sigmas[i]), t_fn(sigmas[i + 1])
 h = t_next - t
 
 t_min = min(sigma_fn(t_next), sigma_fn(t))
 t_max = max(sigma_fn(t_next), sigma_fn(t))

 if old_denoised is None or sigmas[i + 1] == 0:
 x = (t_min / t_max) * x - (-h).expm1() * denoised
 else:
 h_last = t - t_fn(sigmas[i - 1])

 h_min = min(h_last, h)
 h_max = max(h_last, h)
 r = h_max / h_min

 h_d = (h_max + h_min) / 2
 denoised_d = (1 + 1 / (2 * r)) * denoised - (1 / (2 * r)) * old_denoised
 x = (t_min / t_max) * x - (-h_d).expm1() * denoised_d

 old_denoised = denoised
 return x</code></pre></li><li>Scroll all the way to the bottom and paste the code as of the screenshot below then save.</li><li><img src="https://image.civitai.com/xG1nkqKTMzGDvpLrqFT7WA/e9443a54-d320-46de-9587-f876f502a5ff/width=525/e9443a54-d320-46de-9587-f876f502a5ff.jpeg" /><ol><li>Sampler is named dpmpp_2m_alt in ComfyUI.</li></ol></li></ol>

Files with SHA256: 0c65bd18dcb32db01a6aa5e1db3ff2b69ec3247d1770f3dfb51cb6ee8b1c7e85