[Community Pipeline] Batched implementation of Flux with CFG (#9513)

* batched implementation of flux cfg.

* style.

* readme

* remove comments.

examples/community/README.md

@@ -10,6 +10,7 @@ Please also check out our [Community Scripts](https://github.com/huggingface/dif
 
 | Example                                                                                                                               | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              | Code Example                                                                              | Colab                                                                                                                                                                                                              |                                                        Author |
 |:--------------------------------------------------------------------------------------------------------------------------------------|:---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:------------------------------------------------------------------------------------------|:-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------:|
+|Flux with CFG|[Flux with CFG](https://github.com/ToTheBeginning/PuLID/blob/main/docs/pulid_for_flux.md) provides an implementation of using CFG in [Flux](https://blackforestlabs.ai/announcing-black-forest-labs/).|[Flux with CFG](#flux-with-cfg)|NA|[Linoy Tsaban](https://github.com/linoytsaban), [Apolinário](https://github.com/apolinario), and [Sayak Paul](https://github.com/sayakpaul)|
 |Differential Diffusion|[Differential Diffusion](https://github.com/exx8/differential-diffusion) modifies an image according to a text prompt, and according to a map that specifies the amount of change in each region.|[Differential Diffusion](#differential-diffusion)|[![Hugging Face Space](https://img.shields.io/badge/🤗%20Hugging%20Face-Space-yellow)](https://huggingface.co/spaces/exx8/differential-diffusion) [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/exx8/differential-diffusion/blob/main/examples/SD2.ipynb)|[Eran Levin](https://github.com/exx8) and [Ohad Fried](https://www.ohadf.com/)|
 | HD-Painter                                                                                                                            | [HD-Painter](https://github.com/Picsart-AI-Research/HD-Painter) enables prompt-faithfull and high resolution (up to 2k) image inpainting upon any diffusion-based image inpainting method.                                                                                                                                                                                                                                                                                                               | [HD-Painter](#hd-painter)                                                                 | [![Hugging Face Space](https://img.shields.io/badge/🤗%20Hugging%20Face-Space-yellow)](https://huggingface.co/spaces/PAIR/HD-Painter)                                                                              | [Manukyan Hayk](https://github.com/haikmanukyan) and [Sargsyan Andranik](https://github.com/AndranikSargsyan) |
 | Marigold Monocular Depth Estimation                                                                                                   | A universal monocular depth estimator, utilizing Stable Diffusion, delivering sharp predictions in the wild. (See the [project page](https://marigoldmonodepth.github.io) and [full codebase](https://github.com/prs-eth/marigold) for more details.)                                                                                                                                                                                                                                                        | [Marigold Depth Estimation](#marigold-depth-estimation)                                   | [![Hugging Face Space](https://img.shields.io/badge/🤗%20Hugging%20Face-Space-yellow)](https://huggingface.co/spaces/toshas/marigold) [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/drive/12G8reD13DdpMie5ZQlaFNo2WCGeNUH-u?usp=sharing) | [Bingxin Ke](https://github.com/markkua) and [Anton Obukhov](https://github.com/toshas) |
@@ -82,6 +83,36 @@ pipe = DiffusionPipeline.from_pretrained("stable-diffusion-v1-5/stable-diffusion
 
 ## Example usages
 
+### Flux with CFG
+
+Know more about Flux [here](https://blackforestlabs.ai/announcing-black-forest-labs/). Since Flux doesn't use CFG, this implementation provides one, inspired by the [PuLID Flux adaptation](https://github.com/ToTheBeginning/PuLID/blob/main/docs/pulid_for_flux.md).  
+
+Example usage:
+
+```py
+from diffusers import DiffusionPipeline
+import torch 
+
+pipeline = DiffusionPipeline.from_pretrained(
+    "black-forest-labs/FLUX.1-dev", 
+    torch_dtype=torch.bfloat16, 
+    custom_pipeline="pipeline_flux_with_cfg"
+)
+pipeline.enable_model_cpu_offload()
+prompt = "a watercolor painting of a unicorn"
+negative_prompt = "pink"
+
+img = pipeline(
+    prompt=prompt, 
+    negative_prompt=negative_prompt, 
+    true_cfg=1.5, 
+    guidance_scale=3.5, 
+    num_images_per_prompt=1,
+    generator=torch.manual_seed(0)
+).images[0]
+img.save("cfg_flux.png")
+```
+
 ### Differential Diffusion
 
 **Eran Levin, Ohad Fried**

examples/community/pipeline_flux_with_cfg.py

@@ -289,80 +289,104 @@ class FluxCFGPipeline(DiffusionPipeline, FluxLoraLoaderMixin, FromSingleFileMixi
         self,
         prompt: Union[str, List[str]],
         prompt_2: Union[str, List[str]],
+        negative_prompt: Union[str, List[str]] = None,
+        negative_prompt_2: Union[str, List[str]] = None,
         device: Optional[torch.device] = None,
         num_images_per_prompt: int = 1,
         prompt_embeds: Optional[torch.FloatTensor] = None,
         pooled_prompt_embeds: Optional[torch.FloatTensor] = None,
+        negative_prompt_embeds: Optional[torch.FloatTensor] = None,
+        negative_pooled_prompt_embeds: Optional[torch.FloatTensor] = None,
         max_sequence_length: int = 512,
         lora_scale: Optional[float] = None,
+        do_true_cfg: bool = False,
     ):
-        r"""
-
-        Args:
-            prompt (`str` or `List[str]`, *optional*):
-                prompt to be encoded
-            prompt_2 (`str` or `List[str]`, *optional*):
-                The prompt or prompts to be sent to the `tokenizer_2` and `text_encoder_2`. If not defined, `prompt` is
-                used in all text-encoders
-            device: (`torch.device`):
-                torch device
-            num_images_per_prompt (`int`):
-                number of images that should be generated per prompt
-            prompt_embeds (`torch.FloatTensor`, *optional*):
-                Pre-generated text embeddings. Can be used to easily tweak text inputs, *e.g.* prompt weighting. If not
-                provided, text embeddings will be generated from `prompt` input argument.
-            pooled_prompt_embeds (`torch.FloatTensor`, *optional*):
-                Pre-generated pooled text embeddings. Can be used to easily tweak text inputs, *e.g.* prompt weighting.
-                If not provided, pooled text embeddings will be generated from `prompt` input argument.
-            lora_scale (`float`, *optional*):
-                A lora scale that will be applied to all LoRA layers of the text encoder if LoRA layers are loaded.
-        """
         device = device or self._execution_device
 
-        # set lora scale so that monkey patched LoRA
-        # function of text encoder can correctly access it
+        # Set LoRA scale if applicable
         if lora_scale is not None and isinstance(self, FluxLoraLoaderMixin):
             self._lora_scale = lora_scale
 
-            # dynamically adjust the LoRA scale
             if self.text_encoder is not None and USE_PEFT_BACKEND:
                 scale_lora_layers(self.text_encoder, lora_scale)
             if self.text_encoder_2 is not None and USE_PEFT_BACKEND:
                 scale_lora_layers(self.text_encoder_2, lora_scale)
 
         prompt = [prompt] if isinstance(prompt, str) else prompt
+        batch_size = len(prompt)
+
+        if do_true_cfg and negative_prompt is not None:
+            negative_prompt = [negative_prompt] if isinstance(negative_prompt, str) else negative_prompt
+            negative_batch_size = len(negative_prompt)
+
+            if negative_batch_size != batch_size:
+                raise ValueError(
+                    f"Negative prompt batch size ({negative_batch_size}) does not match prompt batch size ({batch_size})"
+                )
+
+            # Concatenate prompts
+            prompts = prompt + negative_prompt
+            prompts_2 = (
+                prompt_2 + negative_prompt_2 if prompt_2 is not None and negative_prompt_2 is not None else None
+            )
+        else:
+            prompts = prompt
+            prompts_2 = prompt_2
 
         if prompt_embeds is None:
-            prompt_2 = prompt_2 or prompt
-            prompt_2 = [prompt_2] if isinstance(prompt_2, str) else prompt_2
+            if prompts_2 is None:
+                prompts_2 = prompts
 
-            # We only use the pooled prompt output from the CLIPTextModel
+            # Get pooled prompt embeddings from CLIPTextModel
             pooled_prompt_embeds = self._get_clip_prompt_embeds(
-                prompt=prompt,
+                prompt=prompts,
                 device=device,
                 num_images_per_prompt=num_images_per_prompt,
             )
             prompt_embeds = self._get_t5_prompt_embeds(
-                prompt=prompt_2,
+                prompt=prompts_2,
                 num_images_per_prompt=num_images_per_prompt,
                 max_sequence_length=max_sequence_length,
                 device=device,
             )
 
+            if do_true_cfg and negative_prompt is not None:
+                # Split embeddings back into positive and negative parts
+                total_batch_size = batch_size * num_images_per_prompt
+                positive_indices = slice(0, total_batch_size)
+                negative_indices = slice(total_batch_size, 2 * total_batch_size)
+
+                positive_pooled_prompt_embeds = pooled_prompt_embeds[positive_indices]
+                negative_pooled_prompt_embeds = pooled_prompt_embeds[negative_indices]
+
+                positive_prompt_embeds = prompt_embeds[positive_indices]
+                negative_prompt_embeds = prompt_embeds[negative_indices]
+
+                pooled_prompt_embeds = positive_pooled_prompt_embeds
+                prompt_embeds = positive_prompt_embeds
+
+        # Unscale LoRA layers
         if self.text_encoder is not None:
             if isinstance(self, FluxLoraLoaderMixin) and USE_PEFT_BACKEND:
-                # Retrieve the original scale by scaling back the LoRA layers
                 unscale_lora_layers(self.text_encoder, lora_scale)
 
         if self.text_encoder_2 is not None:
             if isinstance(self, FluxLoraLoaderMixin) and USE_PEFT_BACKEND:
-                # Retrieve the original scale by scaling back the LoRA layers
                 unscale_lora_layers(self.text_encoder_2, lora_scale)
 
         dtype = self.text_encoder.dtype if self.text_encoder is not None else self.transformer.dtype
         text_ids = torch.zeros(prompt_embeds.shape[1], 3).to(device=device, dtype=dtype)
 
-        return prompt_embeds, pooled_prompt_embeds, text_ids
+        if do_true_cfg and negative_prompt is not None:
+            return (
+                prompt_embeds,
+                pooled_prompt_embeds,
+                text_ids,
+                negative_prompt_embeds,
+                negative_pooled_prompt_embeds,
+            )
+        else:
+            return prompt_embeds, pooled_prompt_embeds, text_ids, None, None
 
     def check_inputs(
         self,
@@ -687,38 +711,33 @@ class FluxCFGPipeline(DiffusionPipeline, FluxLoraLoaderMixin, FromSingleFileMixi
         lora_scale = (
             self.joint_attention_kwargs.get("scale", None) if self.joint_attention_kwargs is not None else None
         )
+        do_true_cfg = true_cfg > 1 and negative_prompt is not None
         (
             prompt_embeds,
             pooled_prompt_embeds,
             text_ids,
+            negative_prompt_embeds,
+            negative_pooled_prompt_embeds,
         ) = self.encode_prompt(
             prompt=prompt,
             prompt_2=prompt_2,
+            negative_prompt=negative_prompt,
+            negative_prompt_2=negative_prompt_2,
             prompt_embeds=prompt_embeds,
             pooled_prompt_embeds=pooled_prompt_embeds,
+            negative_prompt_embeds=negative_prompt_embeds,
+            negative_pooled_prompt_embeds=negative_pooled_prompt_embeds,
             device=device,
             num_images_per_prompt=num_images_per_prompt,
             max_sequence_length=max_sequence_length,
             lora_scale=lora_scale,
+            do_true_cfg=do_true_cfg,
         )
 
-        # perform "real" CFG as suggested for distilled Flux models in https://github.com/ToTheBeginning/PuLID/blob/main/docs/pulid_for_flux.md
-        do_true_cfg = true_cfg > 1 and negative_prompt is not None
         if do_true_cfg:
-            (
-                negative_prompt_embeds,
-                negative_pooled_prompt_embeds,
-                negative_text_ids,
-            ) = self.encode_prompt(
-                prompt=negative_prompt,
-                prompt_2=negative_prompt_2,
-                prompt_embeds=negative_prompt_embeds,
-                pooled_prompt_embeds=negative_pooled_prompt_embeds,
-                device=device,
-                num_images_per_prompt=num_images_per_prompt,
-                max_sequence_length=max_sequence_length,
-                lora_scale=lora_scale,
-            )
+            # Concatenate embeddings
+            prompt_embeds = torch.cat([negative_prompt_embeds, prompt_embeds], dim=0)
+            pooled_prompt_embeds = torch.cat([negative_pooled_prompt_embeds, pooled_prompt_embeds], dim=0)
 
         # 4. Prepare latent variables
         num_channels_latents = self.transformer.config.in_channels // 4
@@ -754,24 +773,26 @@ class FluxCFGPipeline(DiffusionPipeline, FluxLoraLoaderMixin, FromSingleFileMixi
         num_warmup_steps = max(len(timesteps) - num_inference_steps * self.scheduler.order, 0)
         self._num_timesteps = len(timesteps)
 
-        # handle guidance
-        if self.transformer.config.guidance_embeds:
-            guidance = torch.full([1], guidance_scale, device=device, dtype=torch.float32)
-            guidance = guidance.expand(latents.shape[0])
-        else:
-            guidance = None
-
         # 6. Denoising loop
         with self.progress_bar(total=num_inference_steps) as progress_bar:
             for i, t in enumerate(timesteps):
                 if self.interrupt:
                     continue
 
+                latent_model_input = torch.cat([latents] * 2) if do_true_cfg else latents
+
+                # handle guidance
+                if self.transformer.config.guidance_embeds:
+                    guidance = torch.full([1], guidance_scale, device=device, dtype=torch.float32)
+                    guidance = guidance.expand(latent_model_input.shape[0])
+                else:
+                    guidance = None
+
                 # broadcast to batch dimension in a way that's compatible with ONNX/Core ML
-                timestep = t.expand(latents.shape[0]).to(latents.dtype)
+                timestep = t.expand(latent_model_input.shape[0]).to(latent_model_input.dtype)
 
                 noise_pred = self.transformer(
-                    hidden_states=latents,
+                    hidden_states=latent_model_input,
                     timestep=timestep / 1000,
                     guidance=guidance,
                     pooled_projections=pooled_prompt_embeds,
@@ -783,18 +804,7 @@ class FluxCFGPipeline(DiffusionPipeline, FluxLoraLoaderMixin, FromSingleFileMixi
                 )[0]
 
                 if do_true_cfg:
-                    neg_noise_pred = self.transformer(
-                        hidden_states=latents,
-                        timestep=timestep / 1000,
-                        guidance=guidance,
-                        pooled_projections=negative_pooled_prompt_embeds,
-                        encoder_hidden_states=negative_prompt_embeds,
-                        txt_ids=negative_text_ids,
-                        img_ids=latent_image_ids,
-                        joint_attention_kwargs=self.joint_attention_kwargs,
-                        return_dict=False,
-                    )[0]
-
+                    neg_noise_pred, noise_pred = noise_pred.chunk(2)
                     noise_pred = neg_noise_pred + true_cfg * (noise_pred - neg_noise_pred)
 
                 # compute the previous noisy sample x_t -> x_t-1