Flax safety checker (#825)

* Remove set_format in Flax pipeline.

* Remove DummyChecker.

* Run safety_checker in pipeline.

* Don't pmap on every call.

We could have decorated `generate` with `pmap`, but I wanted to keep it
in case someone wants to invoke it in non-parallel mode.

* Remove commented line

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* Replicate outside __call__, prepare for optional jitting.

* Remove unnecessary clipping.

As suggested by @kashif.

* Do not jit unless requested.

* Send all args to generate.

* make style

* Remove unused imports.

* Fix docstring.

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

Author: pcuenca

src/diffusers/pipeline_flax_utils.py

@@ -62,11 +62,6 @@
     ALL_IMPORTABLE_CLASSES.update(LOADABLE_CLASSES[library])
 
 
-class DummyChecker:
-    def __init__(self):
-        self.dummy = True
-
-
 def import_flax_or_no_model(module, class_name):
     try:
         # 1. First make sure that if a Flax object is present, import this one
@@ -177,10 +172,6 @@ def save_pretrained(self, save_directory: Union[str, os.PathLike], params: Union
                 if save_method_name is not None:
                     break
 
-            # TODO(Patrick, Suraj): to delete after
-            if isinstance(sub_model, DummyChecker):
-                continue
-
             save_method = getattr(sub_model, save_method_name)
             expects_params = "params" in set(inspect.signature(save_method).parameters.keys())
 
@@ -194,7 +185,7 @@ def save_pretrained(self, save_directory: Union[str, os.PathLike], params: Union
     @classmethod
     def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.PathLike]], **kwargs):
         r"""
-        Instantiate a PyTorch diffusion pipeline from pre-trained pipeline weights.
+        Instantiate a Flax diffusion pipeline from pre-trained pipeline weights.
 
         The pipeline is set in evaluation mode by default using `model.eval()` (Dropout modules are deactivated).
 
@@ -349,11 +340,6 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
 
         # 3. Load each module in the pipeline
         for name, (library_name, class_name) in init_dict.items():
-            # TODO(Patrick, Suraj) - delete later
-            if class_name == "DummyChecker":
-                library_name = "stable_diffusion"
-                class_name = "FlaxStableDiffusionSafetyChecker"
-
             is_pipeline_module = hasattr(pipelines, library_name)
             loaded_sub_model = None
 
@@ -422,11 +408,7 @@ def from_pretrained(cls, pretrained_model_name_or_path: Optional[Union[str, os.P
                     loaded_sub_model, loaded_params = load_method(loadable_folder, from_pt=from_pt, dtype=dtype)
                     params[name] = loaded_params
                 elif is_transformers_available() and issubclass(class_obj, FlaxPreTrainedModel):
-                    # make sure we don't initialize the weights to save time
-                    if name == "safety_checker":
-                        loaded_sub_model = DummyChecker()
-                        loaded_params = {}
-                    elif from_pt:
+                    if from_pt:
                         # TODO(Suraj): Fix this in Transformers. We should be able to use `_do_init=False` here
                         loaded_sub_model = load_method(loadable_folder, from_pt=from_pt)
                         loaded_params = loaded_sub_model.params

src/diffusers/pipelines/stable_diffusion/pipeline_flax_stable_diffusion.py

@@ -1,8 +1,14 @@
+from functools import partial
 from typing import Dict, List, Optional, Union
 
+import numpy as np
+
 import jax
 import jax.numpy as jnp
 from flax.core.frozen_dict import FrozenDict
+from flax.jax_utils import unreplicate
+from flax.training.common_utils import shard
+from PIL import Image
 from transformers import CLIPFeatureExtractor, CLIPTokenizer, FlaxCLIPTextModel
 
 from ...models import FlaxAutoencoderKL, FlaxUNet2DConditionModel
@@ -77,60 +83,44 @@ def prepare_inputs(self, prompt: Union[str, List[str]]):
         )
         return text_input.input_ids
 
-    def __call__(
+    def _get_safety_scores(self, features, params):
+        special_cos_dist, cos_dist = self.safety_checker(features, params)
+        return (special_cos_dist, cos_dist)
+
+    def _run_safety_checker(self, images, safety_model_params, jit=False):
+        # safety_model_params should already be replicated when jit is True
+        pil_images = [Image.fromarray(image) for image in images]
+        features = self.feature_extractor(pil_images, return_tensors="np").pixel_values
+
+        if jit:
+            features = shard(features)
+            special_cos_dist, cos_dist = _p_get_safety_scores(self, features, safety_model_params)
+            special_cos_dist = unshard(special_cos_dist)
+            cos_dist = unshard(cos_dist)
+            safety_model_params = unreplicate(safety_model_params)
+        else:
+            special_cos_dist, cos_dist = self._get_safety_scores(features, safety_model_params)
+
+        images, has_nsfw = self.safety_checker.filtered_with_scores(
+            special_cos_dist,
+            cos_dist,
+            images,
+            safety_model_params,
+        )
+        return images, has_nsfw
+
+    def _generate(
         self,
         prompt_ids: jnp.array,
         params: Union[Dict, FrozenDict],
         prng_seed: jax.random.PRNGKey,
-        num_inference_steps: Optional[int] = 50,
-        height: Optional[int] = 512,
-        width: Optional[int] = 512,
-        guidance_scale: Optional[float] = 7.5,
+        num_inference_steps: int = 50,
+        height: int = 512,
+        width: int = 512,
+        guidance_scale: float = 7.5,
         latents: Optional[jnp.array] = None,
-        return_dict: bool = True,
         debug: bool = False,
-        **kwargs,
     ):
-        r"""
-        Function invoked when calling the pipeline for generation.
-
-        Args:
-            prompt (`str` or `List[str]`):
-                The prompt or prompts to guide the image generation.
-            height (`int`, *optional*, defaults to 512):
-                The height in pixels of the generated image.
-            width (`int`, *optional*, defaults to 512):
-                The width in pixels of the generated image.
-            num_inference_steps (`int`, *optional*, defaults to 50):
-                The number of denoising steps. More denoising steps usually lead to a higher quality image at the
-                expense of slower inference.
-            guidance_scale (`float`, *optional*, defaults to 7.5):
-                Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
-                `guidance_scale` is defined as `w` of equation 2. of [Imagen
-                Paper](https://arxiv.org/pdf/2205.11487.pdf). 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.
-            generator (`torch.Generator`, *optional*):
-                A [torch generator](https://pytorch.org/docs/stable/generated/torch.Generator.html) to make generation
-                deterministic.
-            latents (`jnp.array`, *optional*):
-                Pre-generated noisy latents, sampled from a Gaussian distribution, to be used as inputs for image
-                generation. Can be used to tweak the same generation with different prompts. If not provided, a latents
-                tensor will ge generated by sampling using the supplied random `generator`.
-            output_type (`str`, *optional*, defaults to `"pil"`):
-                The output format of the generate image. Choose between
-                [PIL](https://pillow.readthedocs.io/en/stable/): `PIL.Image.Image` or `np.array`.
-            return_dict (`bool`, *optional*, defaults to `True`):
-                Whether or not to return a [`~pipelines.stable_diffusion.FlaxStableDiffusionPipelineOutput`] instead of
-                a plain tuple.
-
-        Returns:
-            [`~pipelines.stable_diffusion.FlaxStableDiffusionPipelineOutput`] or `tuple`:
-            [`~pipelines.stable_diffusion.FlaxStableDiffusionPipelineOutput`] if `return_dict` is True, otherwise a
-            `tuple. When returning a tuple, the first element is a list with the generated images, and the second
-            element is a list of `bool`s denoting whether the corresponding generated image likely represents
-            "not-safe-for-work" (nsfw) content, according to the `safety_checker`.
-        """
         if height % 8 != 0 or width % 8 != 0:
             raise ValueError(f"`height` and `width` have to be divisible by 8 but are {height} and {width}.")
 
@@ -203,21 +193,106 @@ def loop_body(step, args):
 
         # scale and decode the image latents with vae
         latents = 1 / 0.18215 * latents
-        # TODO: check when flax vae gets merged into main
         image = self.vae.apply({"params": params["vae"]}, latents, method=self.vae.decode).sample
 
         image = (image / 2 + 0.5).clip(0, 1).transpose(0, 2, 3, 1)
+        return image
 
-        #        image = jnp.asarray(image).transpose(0, 2, 3, 1)
-        # run safety checker
-        # TODO: check when flax safety checker gets merged into main
-        #        safety_checker_input = self.feature_extractor(self.numpy_to_pil(image), return_tensors="np")
-        #        image, has_nsfw_concept = self.safety_checker(
-        #            images=image, clip_input=safety_checker_input.pixel_values, params=params["safety_params"]
-        #        )
-        has_nsfw_concept = False
+    def __call__(
+        self,
+        prompt_ids: jnp.array,
+        params: Union[Dict, FrozenDict],
+        prng_seed: jax.random.PRNGKey,
+        num_inference_steps: int = 50,
+        height: int = 512,
+        width: int = 512,
+        guidance_scale: float = 7.5,
+        latents: jnp.array = None,
+        return_dict: bool = True,
+        jit: bool = False,
+        debug: bool = False,
+        **kwargs,
+    ):
+        r"""
+        Function invoked when calling the pipeline for generation.
+
+        Args:
+            prompt (`str` or `List[str]`):
+                The prompt or prompts to guide the image generation.
+            height (`int`, *optional*, defaults to 512):
+                The height in pixels of the generated image.
+            width (`int`, *optional*, defaults to 512):
+                The width in pixels of the generated image.
+            num_inference_steps (`int`, *optional*, defaults to 50):
+                The number of denoising steps. More denoising steps usually lead to a higher quality image at the
+                expense of slower inference.
+            guidance_scale (`float`, *optional*, defaults to 7.5):
+                Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
+                `guidance_scale` is defined as `w` of equation 2. of [Imagen
+                Paper](https://arxiv.org/pdf/2205.11487.pdf). 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.
+            generator (`torch.Generator`, *optional*):
+                A [torch generator](https://pytorch.org/docs/stable/generated/torch.Generator.html) to make generation
+                deterministic.
+            latents (`jnp.array`, *optional*):
+                Pre-generated noisy latents, sampled from a Gaussian distribution, to be used as inputs for image
+                generation. Can be used to tweak the same generation with different prompts. If not provided, a latents
+                tensor will ge generated by sampling using the supplied random `generator`.
+            output_type (`str`, *optional*, defaults to `"pil"`):
+                The output format of the generate image. Choose between
+                [PIL](https://pillow.readthedocs.io/en/stable/): `PIL.Image.Image` or `np.array`.
+            jit (`bool`, defaults to `False`):
+                Whether to run `pmap` versions of the generation and safety scoring functions. NOTE: This argument
+                exists because `__call__` is not yet end-to-end pmap-able. It will be removed in a future release.
+            return_dict (`bool`, *optional*, defaults to `True`):
+                Whether or not to return a [`~pipelines.stable_diffusion.FlaxStableDiffusionPipelineOutput`] instead of
+                a plain tuple.
+
+        Returns:
+            [`~pipelines.stable_diffusion.FlaxStableDiffusionPipelineOutput`] or `tuple`:
+            [`~pipelines.stable_diffusion.FlaxStableDiffusionPipelineOutput`] if `return_dict` is True, otherwise a
+            `tuple. When returning a tuple, the first element is a list with the generated images, and the second
+            element is a list of `bool`s denoting whether the corresponding generated image likely represents
+            "not-safe-for-work" (nsfw) content, according to the `safety_checker`.
+        """
+        if jit:
+            images = _p_generate(
+                self, prompt_ids, params, prng_seed, num_inference_steps, height, width, guidance_scale, latents, debug
+            )
+        else:
+            images = self._generate(
+                prompt_ids, params, prng_seed, num_inference_steps, height, width, guidance_scale, latents, debug
+            )
+
+        safety_params = params["safety_checker"]
+        images = (images * 255).round().astype("uint8")
+        images = np.asarray(images).reshape(-1, height, width, 3)
+        images, has_nsfw_concept = self._run_safety_checker(images, safety_params, jit)
 
         if not return_dict:
-            return (image, has_nsfw_concept)
+            return (images, has_nsfw_concept)
+
+        return FlaxStableDiffusionPipelineOutput(images=images, nsfw_content_detected=has_nsfw_concept)
+
+
+# TODO: maybe use a config dict instead of so many static argnums
+@partial(jax.pmap, static_broadcasted_argnums=(0, 4, 5, 6, 7, 9))
+def _p_generate(
+    pipe, prompt_ids, params, prng_seed, num_inference_steps, height, width, guidance_scale, latents, debug
+):
+    return pipe._generate(
+        prompt_ids, params, prng_seed, num_inference_steps, height, width, guidance_scale, latents, debug
+    )
+
+
+@partial(jax.pmap, static_broadcasted_argnums=(0,))
+def _p_get_safety_scores(pipe, features, params):
+    return pipe._get_safety_scores(features, params)
+
 
-        return FlaxStableDiffusionPipelineOutput(images=image, nsfw_content_detected=has_nsfw_concept)
+def unshard(x: jnp.ndarray):
+    # einops.rearrange(x, 'd b ... -> (d b) ...')
+    num_devices, batch_size = x.shape[:2]
+    rest = x.shape[2:]
+    return x.reshape(num_devices * batch_size, *rest)