Base code from draft PR

invokeai/app/invocations/denoise_latents.py

@@ -1,5 +1,6 @@
 # Copyright (c) 2023 Kyle Schouviller (https://github.com/kyle0654)
 import inspect
+import os
 from contextlib import ExitStack
 from typing import Any, Dict, Iterator, List, Optional, Tuple, Union
 
@@ -39,6 +40,7 @@ from invokeai.backend.lora import LoRAModelRaw
 from invokeai.backend.model_manager import BaseModelType
 from invokeai.backend.model_patcher import ModelPatcher
 from invokeai.backend.stable_diffusion import PipelineIntermediateState, set_seamless
+from invokeai.backend.stable_diffusion.denoise_context import DenoiseContext
 from invokeai.backend.stable_diffusion.diffusers_pipeline import (
     ControlNetData,
     StableDiffusionGeneratorPipeline,
@@ -53,6 +55,9 @@ from invokeai.backend.stable_diffusion.diffusion.conditioning_data import (
     TextConditioningData,
     TextConditioningRegions,
 )
+from invokeai.backend.stable_diffusion.diffusion.custom_atttention import CustomAttnProcessor2_0
+from invokeai.backend.stable_diffusion.diffusion_backend import StableDiffusionBackend
+from invokeai.backend.stable_diffusion.extensions_manager import ExtensionsManager
 from invokeai.backend.stable_diffusion.schedulers import SCHEDULER_MAP
 from invokeai.backend.stable_diffusion.schedulers.schedulers import SCHEDULER_NAME_VALUES
 from invokeai.backend.util.devices import TorchDevice
@@ -314,9 +319,10 @@ class DenoiseLatentsInvocation(BaseInvocation):
         context: InvocationContext,
         positive_conditioning_field: Union[ConditioningField, list[ConditioningField]],
         negative_conditioning_field: Union[ConditioningField, list[ConditioningField]],
-        unet: UNet2DConditionModel,
         latent_height: int,
         latent_width: int,
+        device: torch.device,
+        dtype: torch.dtype,
         cfg_scale: float | list[float],
         steps: int,
         cfg_rescale_multiplier: float,
@@ -330,10 +336,10 @@ class DenoiseLatentsInvocation(BaseInvocation):
             uncond_list = [uncond_list]
 
         cond_text_embeddings, cond_text_embedding_masks = DenoiseLatentsInvocation._get_text_embeddings_and_masks(
-            cond_list, context, unet.device, unet.dtype
+            cond_list, context, device, dtype
         )
         uncond_text_embeddings, uncond_text_embedding_masks = DenoiseLatentsInvocation._get_text_embeddings_and_masks(
-            uncond_list, context, unet.device, unet.dtype
+            uncond_list, context, device, dtype
         )
 
         cond_text_embedding, cond_regions = DenoiseLatentsInvocation._concat_regional_text_embeddings(
@@ -341,14 +347,14 @@ class DenoiseLatentsInvocation(BaseInvocation):
             masks=cond_text_embedding_masks,
             latent_height=latent_height,
             latent_width=latent_width,
-            dtype=unet.dtype,
+            dtype=dtype,
         )
         uncond_text_embedding, uncond_regions = DenoiseLatentsInvocation._concat_regional_text_embeddings(
             text_conditionings=uncond_text_embeddings,
             masks=uncond_text_embedding_masks,
             latent_height=latent_height,
             latent_width=latent_width,
-            dtype=unet.dtype,
+            dtype=dtype,
         )
 
         if isinstance(cfg_scale, list):
@@ -707,9 +713,99 @@ class DenoiseLatentsInvocation(BaseInvocation):
 
         return seed, noise, latents
 
+    def invoke(self, context: InvocationContext) -> LatentsOutput:
+        if os.environ.get("USE_MODULAR_DENOISE", False):
+            return self._new_invoke(context)
+        else:
+            return self._old_invoke(context)
+
     @torch.no_grad()
     @SilenceWarnings()  # This quenches the NSFW nag from diffusers.
-    def invoke(self, context: InvocationContext) -> LatentsOutput:
+    def _new_invoke(self, context: InvocationContext) -> LatentsOutput:
+        with ExitStack() as exit_stack:
+            ext_manager = ExtensionsManager()
+
+            device = TorchDevice.choose_torch_device()
+            dtype = TorchDevice.choose_torch_dtype()
+
+            seed, noise, latents = self.prepare_noise_and_latents(context, self.noise, self.latents)
+            latents = latents.to(device=device, dtype=dtype)
+            if noise is not None:
+                noise = noise.to(device=device, dtype=dtype)
+
+            _, _, latent_height, latent_width = latents.shape
+
+            conditioning_data = self.get_conditioning_data(
+                context=context,
+                positive_conditioning_field=self.positive_conditioning,
+                negative_conditioning_field=self.negative_conditioning,
+                cfg_scale=self.cfg_scale,
+                steps=self.steps,
+                latent_height=latent_height,
+                latent_width=latent_width,
+                device=device,
+                dtype=dtype,
+                # TODO: old backend, remove
+                cfg_rescale_multiplier=self.cfg_rescale_multiplier,
+            )
+
+            scheduler = get_scheduler(
+                context=context,
+                scheduler_info=self.unet.scheduler,
+                scheduler_name=self.scheduler,
+                seed=seed,
+            )
+
+            timesteps, init_timestep, scheduler_step_kwargs = self.init_scheduler(
+                scheduler,
+                seed=seed,
+                device=device,
+                steps=self.steps,
+                denoising_start=self.denoising_start,
+                denoising_end=self.denoising_end,
+            )
+
+            denoise_ctx = DenoiseContext(
+                latents=latents,
+                timesteps=timesteps,
+                init_timestep=init_timestep,
+                noise=noise,
+                seed=seed,
+                scheduler_step_kwargs=scheduler_step_kwargs,
+                conditioning_data=conditioning_data,
+                unet=None,
+                scheduler=scheduler,
+            )
+
+            # get the unet's config so that we can pass the base to sd_step_callback()
+            unet_config = context.models.get_config(self.unet.unet.key)
+
+            # ext: t2i/ip adapter
+            ext_manager.modifiers.pre_unet_load(denoise_ctx, ext_manager)
+
+            unet_info = context.models.load(self.unet.unet)
+            assert isinstance(unet_info.model, UNet2DConditionModel)
+            with (
+                unet_info.model_on_device() as (model_state_dict, unet),
+                # ext: controlnet
+                ext_manager.patch_attention_processor(unet, CustomAttnProcessor2_0),
+                # ext: freeu, seamless, ip adapter, lora
+                ext_manager.patch_unet(model_state_dict, unet),
+            ):
+                sd_backend = StableDiffusionBackend(unet, scheduler)
+                denoise_ctx.unet = unet
+                result_latents = sd_backend.latents_from_embeddings(denoise_ctx, ext_manager)
+
+        # https://discuss.huggingface.co/t/memory-usage-by-later-pipeline-stages/23699
+        result_latents = result_latents.to("cpu")  # TODO: detach?
+        TorchDevice.empty_cache()
+
+        name = context.tensors.save(tensor=result_latents)
+        return LatentsOutput.build(latents_name=name, latents=result_latents, seed=None)
+
+    @torch.no_grad()
+    @SilenceWarnings()  # This quenches the NSFW nag from diffusers.
+    def _old_invoke(self, context: InvocationContext) -> LatentsOutput:
         seed, noise, latents = self.prepare_noise_and_latents(context, self.noise, self.latents)
 
         mask, masked_latents, gradient_mask = self.prep_inpaint_mask(context, latents)
@@ -788,7 +884,8 @@ class DenoiseLatentsInvocation(BaseInvocation):
                 context=context,
                 positive_conditioning_field=self.positive_conditioning,
                 negative_conditioning_field=self.negative_conditioning,
-                unet=unet,
+                device=unet.device,
+                dtype=unet.dtype,
                 latent_height=latent_height,
                 latent_width=latent_width,
                 cfg_scale=self.cfg_scale,

invokeai/backend/stable_diffusion/denoise_context.py

@@ -0,0 +1,60 @@
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import TYPE_CHECKING, Any, Dict, Optional, Tuple, Union
+
+import torch
+from diffusers import UNet2DConditionModel
+from diffusers.schedulers.scheduling_utils import SchedulerMixin, SchedulerOutput
+
+if TYPE_CHECKING:
+    from invokeai.backend.stable_diffusion.diffusion.conditioning_data import TextConditioningData
+
+
+@dataclass
+class UNetKwargs:
+    sample: torch.Tensor
+    timestep: Union[torch.Tensor, float, int]
+    encoder_hidden_states: torch.Tensor
+
+    class_labels: Optional[torch.Tensor] = None
+    timestep_cond: Optional[torch.Tensor] = None
+    attention_mask: Optional[torch.Tensor] = None
+    cross_attention_kwargs: Optional[Dict[str, Any]] = None
+    added_cond_kwargs: Optional[Dict[str, torch.Tensor]] = None
+    down_block_additional_residuals: Optional[Tuple[torch.Tensor]] = None
+    mid_block_additional_residual: Optional[torch.Tensor] = None
+    down_intrablock_additional_residuals: Optional[Tuple[torch.Tensor]] = None
+    encoder_attention_mask: Optional[torch.Tensor] = None
+    # return_dict: bool = True
+
+
+@dataclass
+class DenoiseContext:
+    latents: torch.Tensor
+    scheduler_step_kwargs: dict[str, Any]
+    conditioning_data: TextConditioningData
+    noise: Optional[torch.Tensor]
+    seed: int
+    timesteps: torch.Tensor
+    init_timestep: torch.Tensor
+
+    scheduler: SchedulerMixin
+    unet: Optional[UNet2DConditionModel] = None
+
+    orig_latents: Optional[torch.Tensor] = None
+    step_index: Optional[int] = None
+    timestep: Optional[torch.Tensor] = None
+    unet_kwargs: Optional[UNetKwargs] = None
+    step_output: Optional[SchedulerOutput] = None
+
+    latent_model_input: Optional[torch.Tensor] = None
+    conditioning_mode: Optional[str] = None
+    negative_noise_pred: Optional[torch.Tensor] = None
+    positive_noise_pred: Optional[torch.Tensor] = None
+    noise_pred: Optional[torch.Tensor] = None
+
+    extra: dict = field(default_factory=dict)
+
+    def __delattr__(self, name: str):
+        setattr(self, name, None)

invokeai/backend/stable_diffusion/diffusion/conditioning_data.py

@@ -5,6 +5,7 @@ from typing import List, Optional, Union
 import torch
 
 from invokeai.backend.ip_adapter.ip_adapter import IPAdapter
+from invokeai.backend.stable_diffusion.diffusion.regional_prompt_data import RegionalPromptData
 
 
 @dataclass
@@ -103,7 +104,7 @@ class TextConditioningData:
         uncond_regions: Optional[TextConditioningRegions],
         cond_regions: Optional[TextConditioningRegions],
         guidance_scale: Union[float, List[float]],
-        guidance_rescale_multiplier: float = 0,
+        guidance_rescale_multiplier: float = 0,  # TODO: old backend, remove
     ):
         self.uncond_text = uncond_text
         self.cond_text = cond_text
@@ -114,6 +115,7 @@ class TextConditioningData:
         # Guidance scale is enabled by setting `guidance_scale > 1`. Higher guidance scale encourages to generate
         # images that are closely linked to the text `prompt`, usually at the expense of lower image quality.
         self.guidance_scale = guidance_scale
+        # TODO: old backend, remove
         # For models trained using zero-terminal SNR ("ztsnr"), it's suggested to use guidance_rescale_multiplier of 0.7.
         # See [Common Diffusion Noise Schedules and Sample Steps are Flawed](https://arxiv.org/pdf/2305.08891.pdf).
         self.guidance_rescale_multiplier = guidance_rescale_multiplier
@@ -121,3 +123,127 @@ class TextConditioningData:
     def is_sdxl(self):
         assert isinstance(self.uncond_text, SDXLConditioningInfo) == isinstance(self.cond_text, SDXLConditioningInfo)
         return isinstance(self.cond_text, SDXLConditioningInfo)
+
+    def to_unet_kwargs(self, unet_kwargs, conditioning_mode):
+        if conditioning_mode == "both":
+            encoder_hidden_states, encoder_attention_mask = self._concat_conditionings_for_batch(
+                self.uncond_text.embeds, self.cond_text.embeds
+            )
+        elif conditioning_mode == "positive":
+            encoder_hidden_states = self.cond_text.embeds
+            encoder_attention_mask = None
+        else:  # elif conditioning_mode == "negative":
+            encoder_hidden_states = self.uncond_text.embeds
+            encoder_attention_mask = None
+
+        unet_kwargs.encoder_hidden_states = encoder_hidden_states
+        unet_kwargs.encoder_attention_mask = encoder_attention_mask
+
+        if self.is_sdxl():
+            if conditioning_mode == "negative":
+                added_cond_kwargs = dict(  # noqa: C408
+                    text_embeds=self.cond_text.pooled_embeds,
+                    time_ids=self.cond_text.add_time_ids,
+                )
+            elif conditioning_mode == "positive":
+                added_cond_kwargs = dict(  # noqa: C408
+                    text_embeds=self.uncond_text.pooled_embeds,
+                    time_ids=self.uncond_text.add_time_ids,
+                )
+            else:  # elif conditioning_mode == "both":
+                added_cond_kwargs = dict(  # noqa: C408
+                    text_embeds=torch.cat(
+                        [
+                            # TODO: how to pad? just by zeros? or even truncate?
+                            self.uncond_text.pooled_embeds,
+                            self.cond_text.pooled_embeds,
+                        ],
+                    ),
+                    time_ids=torch.cat(
+                        [
+                            self.uncond_text.add_time_ids,
+                            self.cond_text.add_time_ids,
+                        ],
+                    ),
+                )
+
+            unet_kwargs.added_cond_kwargs = added_cond_kwargs
+
+        if self.cond_regions is not None or self.uncond_regions is not None:
+            # TODO(ryand): We currently initialize RegionalPromptData for every denoising step. The text conditionings
+            # and masks are not changing from step-to-step, so this really only needs to be done once. While this seems
+            # painfully inefficient, the time spent is typically negligible compared to the forward inference pass of
+            # the UNet. The main reason that this hasn't been moved up to eliminate redundancy is that it is slightly
+            # awkward to handle both standard conditioning and sequential conditioning further up the stack.
+
+            _tmp_regions = self.cond_regions if self.cond_regions is not None else self.uncond_regions
+            _, _, h, w = _tmp_regions.masks.shape
+            dtype = self.cond_text.embeds.dtype
+            device = self.cond_text.embeds.device
+
+            regions = []
+            for c, r in [
+                (self.uncond_text, self.uncond_regions),
+                (self.cond_text, self.cond_regions),
+            ]:
+                if r is None:
+                    # Create a dummy mask and range for text conditioning that doesn't have region masks.
+                    r = TextConditioningRegions(
+                        masks=torch.ones((1, 1, h, w), dtype=dtype),
+                        ranges=[Range(start=0, end=c.embeds.shape[1])],
+                    )
+                regions.append(r)
+
+            if unet_kwargs.cross_attention_kwargs is None:
+                unet_kwargs.cross_attention_kwargs = {}
+
+            unet_kwargs.cross_attention_kwargs.update(
+                regional_prompt_data=RegionalPromptData(regions=regions, device=device, dtype=dtype),
+            )
+
+    def _concat_conditionings_for_batch(self, unconditioning, conditioning):
+        def _pad_conditioning(cond, target_len, encoder_attention_mask):
+            conditioning_attention_mask = torch.ones(
+                (cond.shape[0], cond.shape[1]), device=cond.device, dtype=cond.dtype
+            )
+
+            if cond.shape[1] < max_len:
+                conditioning_attention_mask = torch.cat(
+                    [
+                        conditioning_attention_mask,
+                        torch.zeros((cond.shape[0], max_len - cond.shape[1]), device=cond.device, dtype=cond.dtype),
+                    ],
+                    dim=1,
+                )
+
+                cond = torch.cat(
+                    [
+                        cond,
+                        torch.zeros(
+                            (cond.shape[0], max_len - cond.shape[1], cond.shape[2]),
+                            device=cond.device,
+                            dtype=cond.dtype,
+                        ),
+                    ],
+                    dim=1,
+                )
+
+            if encoder_attention_mask is None:
+                encoder_attention_mask = conditioning_attention_mask
+            else:
+                encoder_attention_mask = torch.cat(
+                    [
+                        encoder_attention_mask,
+                        conditioning_attention_mask,
+                    ]
+                )
+
+            return cond, encoder_attention_mask
+
+        encoder_attention_mask = None
+        if unconditioning.shape[1] != conditioning.shape[1]:
+            max_len = max(unconditioning.shape[1], conditioning.shape[1])
+            unconditioning, encoder_attention_mask = _pad_conditioning(unconditioning, max_len, encoder_attention_mask)
+            conditioning, encoder_attention_mask = _pad_conditioning(conditioning, max_len, encoder_attention_mask)
+
+        return torch.cat([unconditioning, conditioning]), encoder_attention_mask

invokeai/backend/stable_diffusion/diffusion/regional_prompt_data.py

@@ -1,9 +1,14 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
 import torch
 import torch.nn.functional as F
 
-from invokeai.backend.stable_diffusion.diffusion.conditioning_data import (
+if TYPE_CHECKING:
-    TextConditioningRegions,
+    from invokeai.backend.stable_diffusion.diffusion.conditioning_data import (
-)
+        TextConditioningRegions,
+    )
 
 
 class RegionalPromptData:

invokeai/backend/stable_diffusion/diffusion_backend.py

@@ -0,0 +1,220 @@
+from __future__ import annotations
+
+import PIL.Image
+import torch
+import torchvision.transforms as T
+from diffusers.models.unets.unet_2d_condition import UNet2DConditionModel
+from diffusers.schedulers.scheduling_utils import SchedulerMixin, SchedulerOutput
+from tqdm.auto import tqdm
+
+from invokeai.app.services.config.config_default import get_config
+from invokeai.backend.stable_diffusion.denoise_context import DenoiseContext, UNetKwargs
+from invokeai.backend.stable_diffusion.extensions_manager import ExtensionsManager
+
+
+def trim_to_multiple_of(*args, multiple_of=8):
+    return tuple((x - x % multiple_of) for x in args)
+
+
+def image_resized_to_grid_as_tensor(image: PIL.Image.Image, normalize: bool = True, multiple_of=8) -> torch.FloatTensor:
+    """
+
+    :param image: input image
+    :param normalize: scale the range to [-1, 1] instead of [0, 1]
+    :param multiple_of: resize the input so both dimensions are a multiple of this
+    """
+    w, h = trim_to_multiple_of(*image.size, multiple_of=multiple_of)
+    transformation = T.Compose(
+        [
+            T.Resize((h, w), T.InterpolationMode.LANCZOS, antialias=True),
+            T.ToTensor(),
+        ]
+    )
+    tensor = transformation(image)
+    if normalize:
+        tensor = tensor * 2.0 - 1.0
+    return tensor
+
+
+class StableDiffusionBackend:
+    def __init__(
+        self,
+        unet: UNet2DConditionModel,
+        scheduler: SchedulerMixin,
+    ):
+        self.unet = unet
+        self.scheduler = scheduler
+        config = get_config()
+        self.sequential_guidance = config.sequential_guidance
+
+    def latents_from_embeddings(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
+        if ctx.init_timestep.shape[0] == 0:
+            return ctx.latents
+
+        ctx.orig_latents = ctx.latents.clone()
+
+        if ctx.noise is not None:
+            batch_size = ctx.latents.shape[0]
+            # latents = noise * self.scheduler.init_noise_sigma # it's like in t2l according to diffusers
+            ctx.latents = ctx.scheduler.add_noise(ctx.latents, ctx.noise, ctx.init_timestep.expand(batch_size))
+
+        # if no work to do, return latents
+        if ctx.timesteps.shape[0] == 0:
+            return ctx.latents
+
+        # ext: inpaint[pre_denoise_loop, priority=normal] (maybe init, but not sure if it needed)
+        # ext: preview[pre_denoise_loop, priority=low]
+        ext_manager.modifiers.pre_denoise_loop(ctx)
+
+        for ctx.step_index, ctx.timestep in enumerate(tqdm(ctx.timesteps)):  # noqa: B020
+            # ext: inpaint (apply mask to latents on non-inpaint models)
+            ext_manager.modifiers.pre_step(ctx)
+
+            # ext: tiles? [override: step]
+            ctx.step_output = ext_manager.overrides.step(self.step, ctx, ext_manager)
+
+            # ext: inpaint[post_step, priority=high] (apply mask to preview on non-inpaint models)
+            # ext: preview[post_step, priority=low]
+            ext_manager.modifiers.post_step(ctx)
+
+            ctx.latents = ctx.step_output.prev_sample
+
+        # ext: inpaint[post_denoise_loop] (restore unmasked part)
+        ext_manager.modifiers.post_denoise_loop(ctx)
+        return ctx.latents
+
+    @torch.inference_mode()
+    def step(self, ctx: DenoiseContext, ext_manager: ExtensionsManager) -> SchedulerOutput:
+        ctx.latent_model_input = ctx.scheduler.scale_model_input(ctx.latents, ctx.timestep)
+
+        if self.sequential_guidance:
+            conditioning_call = self._apply_standard_conditioning_sequentially
+        else:
+            conditioning_call = self._apply_standard_conditioning
+
+        # not sure if here needed override
+        ctx.negative_noise_pred, ctx.positive_noise_pred = conditioning_call(ctx, ext_manager)
+
+        # ext: override combine_noise
+        ctx.noise_pred = ext_manager.overrides.combine_noise(self.combine_noise, ctx)
+
+        # ext: cfg_rescale [modify_noise_prediction]
+        ext_manager.modifiers.modify_noise_prediction(ctx)
+
+        # compute the previous noisy sample x_t -> x_t-1
+        step_output = ctx.scheduler.step(ctx.noise_pred, ctx.timestep, ctx.latents, **ctx.scheduler_step_kwargs)
+
+        # del locals
+        del ctx.latent_model_input
+        del ctx.negative_noise_pred
+        del ctx.positive_noise_pred
+        del ctx.noise_pred
+
+        return step_output
+
+    @staticmethod
+    def combine_noise(ctx: DenoiseContext) -> torch.Tensor:
+        guidance_scale = ctx.conditioning_data.guidance_scale
+        if isinstance(guidance_scale, list):
+            guidance_scale = guidance_scale[ctx.step_index]
+
+        return torch.lerp(ctx.negative_noise_pred, ctx.positive_noise_pred, guidance_scale)
+        # return ctx.negative_noise_pred + guidance_scale * (ctx.positive_noise_pred - ctx.negative_noise_pred)
+
+    def _apply_standard_conditioning(
+        self, ctx: DenoiseContext, ext_manager: ExtensionsManager
+    ) -> tuple[torch.Tensor, torch.Tensor]:
+        """Runs the conditioned and unconditioned UNet forward passes in a single batch for faster inference speed at
+        the cost of higher memory usage.
+        """
+
+        ctx.unet_kwargs = UNetKwargs(
+            sample=torch.cat([ctx.latent_model_input] * 2),
+            timestep=ctx.timestep,
+            encoder_hidden_states=None,  # set later by conditoning
+            cross_attention_kwargs=dict(  # noqa: C408
+                percent_through=ctx.step_index / len(ctx.timesteps),  # ctx.total_steps,
+            ),
+        )
+
+        ctx.conditioning_mode = "both"
+        ctx.conditioning_data.to_unet_kwargs(ctx.unet_kwargs, ctx.conditioning_mode)
+
+        # ext: controlnet/ip/t2i [pre_unet_forward]
+        ext_manager.modifiers.pre_unet_forward(ctx)
+
+        # ext: inpaint [pre_unet_forward, priority=low]
+        # or
+        # ext: inpaint [override: unet_forward]
+        both_results = self._unet_forward(**vars(ctx.unet_kwargs))
+        negative_next_x, positive_next_x = both_results.chunk(2)
+        # del locals
+        del ctx.unet_kwargs
+        del ctx.conditioning_mode
+        return negative_next_x, positive_next_x
+
+    def _apply_standard_conditioning_sequentially(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
+        """Runs the conditioned and unconditioned UNet forward passes sequentially for lower memory usage at the cost of
+        slower execution speed.
+        """
+
+        ###################
+        # Negative pass
+        ###################
+
+        ctx.unet_kwargs = UNetKwargs(
+            sample=ctx.latent_model_input,
+            timestep=ctx.timestep,
+            encoder_hidden_states=None,  # set later by conditoning
+            cross_attention_kwargs=dict(  # noqa: C408
+                percent_through=ctx.step_index / len(ctx.timesteps),  # ctx.total_steps,
+            ),
+        )
+
+        ctx.conditioning_mode = "negative"
+        ctx.conditioning_data.to_unet_kwargs(ctx.unet_kwargs, "negative")
+
+        # ext: controlnet/ip/t2i [pre_unet_forward]
+        ext_manager.modifiers.pre_unet_forward(ctx)
+
+        # ext: inpaint [pre_unet_forward, priority=low]
+        # or
+        # ext: inpaint [override: unet_forward]
+        negative_next_x = self._unet_forward(**vars(ctx.unet_kwargs))
+
+        del ctx.unet_kwargs
+        del ctx.conditioning_mode
+        # TODO: gc.collect() ?
+
+        ###################
+        # Positive pass
+        ###################
+
+        ctx.unet_kwargs = UNetKwargs(
+            sample=ctx.latent_model_input,
+            timestep=ctx.timestep,
+            encoder_hidden_states=None,  # set later by conditoning
+            cross_attention_kwargs=dict(  # noqa: C408
+                percent_through=ctx.step_index / len(ctx.timesteps),  # ctx.total_steps,
+            ),
+        )
+
+        ctx.conditioning_mode = "positive"
+        ctx.conditioning_data.to_unet_kwargs(ctx.unet_kwargs, "positive")
+
+        # ext: controlnet/ip/t2i [pre_unet_forward]
+        ext_manager.modifiers.pre_unet_forward(ctx)
+
+        # ext: inpaint [pre_unet_forward, priority=low]
+        # or
+        # ext: inpaint [override: unet_forward]
+        positive_next_x = self._unet_forward(**vars(ctx.unet_kwargs))
+
+        del ctx.unet_kwargs
+        del ctx.conditioning_mode
+        # TODO: gc.collect() ?
+
+        return negative_next_x, positive_next_x
+
+    def _unet_forward(self, **kwargs) -> torch.Tensor:
+        return self.unet(**kwargs).sample

invokeai/backend/stable_diffusion/extensions/__init__.py

@@ -0,0 +1,9 @@
+"""
+Initialization file for the invokeai.backend.stable_diffusion.extensions package
+"""
+
+from invokeai.backend.stable_diffusion.extensions.base import ExtensionBase
+
+__all__ = [
+    "ExtensionBase",
+]

invokeai/backend/stable_diffusion/extensions/base.py

@@ -0,0 +1,58 @@
+from contextlib import contextmanager
+from dataclasses import dataclass
+from typing import Callable, Dict, List, Optional
+
+import torch
+from diffusers import UNet2DConditionModel
+
+
+@dataclass
+class InjectionInfo:
+    type: str
+    name: str
+    order: Optional[str]
+    function: Callable
+
+
+def modifier(name: str, order: str = "any"):
+    def _decorator(func):
+        func.__inj_info__ = {
+            "type": "modifier",
+            "name": name,
+            "order": order,
+        }
+        return func
+
+    return _decorator
+
+
+def override(name: str):
+    def _decorator(func):
+        func.__inj_info__ = {
+            "type": "override",
+            "name": name,
+            "order": None,
+        }
+        return func
+
+    return _decorator
+
+
+class ExtensionBase:
+    def __init__(self, priority: int):
+        self.priority = priority
+        self.injections: List[InjectionInfo] = []
+        for func_name in dir(self):
+            func = getattr(self, func_name)
+            if not callable(func) or not hasattr(func, "__inj_info__"):
+                continue
+
+            self.injections.append(InjectionInfo(**func.__inj_info__, function=func))
+
+    @contextmanager
+    def patch_attention_processor(self, attention_processor_cls: object):
+        yield None
+
+    @contextmanager
+    def patch_unet(self, state_dict: Dict[str, torch.Tensor], unet: UNet2DConditionModel):
+        yield None

invokeai/backend/stable_diffusion/extensions_manager.py

@@ -0,0 +1,195 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from contextlib import ExitStack, contextmanager
+from functools import partial
+from typing import TYPE_CHECKING, Callable, Dict
+
+import torch
+from diffusers import UNet2DConditionModel
+
+from invokeai.backend.util.devices import TorchDevice
+
+if TYPE_CHECKING:
+    from invokeai.backend.stable_diffusion.denoise_context import DenoiseContext
+    from invokeai.backend.stable_diffusion.extensions import ExtensionBase
+
+
+class ExtModifiersApi(ABC):
+    @abstractmethod
+    def pre_denoise_loop(self, ctx: DenoiseContext):
+        pass
+
+    @abstractmethod
+    def post_denoise_loop(self, ctx: DenoiseContext):
+        pass
+
+    @abstractmethod
+    def pre_step(self, ctx: DenoiseContext):
+        pass
+
+    @abstractmethod
+    def post_step(self, ctx: DenoiseContext):
+        pass
+
+    @abstractmethod
+    def modify_noise_prediction(self, ctx: DenoiseContext):
+        pass
+
+    @abstractmethod
+    def pre_unet_forward(self, ctx: DenoiseContext):
+        pass
+
+    @abstractmethod
+    def pre_unet_load(self, ctx: DenoiseContext, ext_manager: ExtensionsManager):
+        pass
+
+
+class ExtOverridesApi(ABC):
+    @abstractmethod
+    def step(self, orig_func: Callable, ctx: DenoiseContext, ext_manager: ExtensionsManager):
+        pass
+
+    @abstractmethod
+    def combine_noise(self, orig_func: Callable, ctx: DenoiseContext):
+        pass
+
+
+class ProxyCallsClass:
+    def __init__(self, handler):
+        self._handler = handler
+
+    def __getattr__(self, item):
+        return partial(self._handler, item)
+
+
+class ModifierInjectionPoint:
+    def __init__(self):
+        self.first = []
+        self.any = []
+        self.last = []
+
+    def add(self, func: Callable, order: str):
+        if order == "first":
+            self.first.append(func)
+        elif order == "last":
+            self.last.append(func)
+        else:  # elif order == "any":
+            self.any.append(func)
+
+    def __call__(self, *args, **kwargs):
+        for func in self.first:
+            func(*args, **kwargs)
+        for func in self.any:
+            func(*args, **kwargs)
+        for func in reversed(self.last):
+            func(*args, **kwargs)
+
+
+class ExtensionsManager:
+    def __init__(self):
+        self.extensions = []
+
+        self._overrides = {}
+        self._modifiers = {}
+
+        self.modifiers: ExtModifiersApi = ProxyCallsClass(self.call_modifier)
+        self.overrides: ExtOverridesApi = ProxyCallsClass(self.call_override)
+
+    def add_extension(self, ext: ExtensionBase):
+        self.extensions.append(ext)
+        ordered_extensions = sorted(self.extensions, reverse=True, key=lambda ext: ext.priority)
+
+        self._overrides.clear()
+        self._modifiers.clear()
+
+        for ext in ordered_extensions:
+            for inj_info in ext.injections:
+                if inj_info.type == "modifier":
+                    if inj_info.name not in self._modifiers:
+                        self._modifiers[inj_info.name] = ModifierInjectionPoint()
+                    self._modifiers[inj_info.name].add(inj_info.function, inj_info.order)
+
+                else:
+                    if inj_info.name in self._overrides:
+                        raise Exception(f"Already overloaded - {inj_info.name}")
+                    self._overrides[inj_info.name] = inj_info.function
+
+    def call_modifier(self, name: str, *args, **kwargs):
+        if name in self._modifiers:
+            self._modifiers[name](*args, **kwargs)
+
+    def call_override(self, name: str, orig_func: Callable, *args, **kwargs):
+        if name in self._overrides:
+            return self._overrides[name](orig_func, *args, **kwargs)
+        else:
+            return orig_func(*args, **kwargs)
+
+    # TODO: is there any need in such high abstarction
+    # @contextmanager
+    # def patch_extensions(self):
+    #    exit_stack = ExitStack()
+    #    try:
+    #        for ext in self.extensions:
+    #            exit_stack.enter_context(ext.patch_extension(self))
+    #
+    #        yield None
+    #
+    #    finally:
+    #        exit_stack.close()
+
+    @contextmanager
+    def patch_attention_processor(self, unet: UNet2DConditionModel, attn_processor_cls: object):
+        unet_orig_processors = unet.attn_processors
+        exit_stack = ExitStack()
+        try:
+            # just to be sure that attentions have not same processor instance
+            attn_procs = {}
+            for name in unet.attn_processors.keys():
+                attn_procs[name] = attn_processor_cls()
+            unet.set_attn_processor(attn_procs)
+
+            for ext in self.extensions:
+                exit_stack.enter_context(ext.patch_attention_processor(attn_processor_cls))
+
+            yield None
+
+        finally:
+            unet.set_attn_processor(unet_orig_processors)
+            exit_stack.close()
+
+    @contextmanager
+    def patch_unet(self, state_dict: Dict[str, torch.Tensor], unet: UNet2DConditionModel):
+        exit_stack = ExitStack()
+        try:
+            changed_keys = set()
+            changed_unknown_keys = {}
+
+            ordered_extensions = sorted(self.extensions, reverse=True, key=lambda ext: ext.priority)
+            for ext in ordered_extensions:
+                patch_result = exit_stack.enter_context(ext.patch_unet(state_dict, unet))
+                if patch_result is None:
+                    continue
+                new_keys, new_unk_keys = patch_result
+                changed_keys.update(new_keys)
+                # skip already seen keys, as new weight might be changed
+                for k, v in new_unk_keys.items():
+                    if k in changed_unknown_keys:
+                        continue
+                    changed_unknown_keys[k] = v
+
+            yield None
+
+        finally:
+            exit_stack.close()
+            assert hasattr(unet, "get_submodule")  # mypy not picking up fact that torch.nn.Module has get_submodule()
+            with torch.no_grad():
+                for module_key in changed_keys:
+                    weight = state_dict[module_key]
+                    unet.get_submodule(module_key).weight.copy_(
+                        weight, non_blocking=TorchDevice.get_non_blocking(weight.device)
+                    )
+                for module_key, weight in changed_unknown_keys.items():
+                    unet.get_submodule(module_key).weight.copy_(
+                        weight, non_blocking=TorchDevice.get_non_blocking(weight.device)
+                    )