update the clip guided PR according to the new API (#751)

Author: patil-suraj

examples/community/clip_guided_stable_diffusion.py

@@ -175,6 +175,7 @@ def __call__(
         width: Optional[int] = 512,
         num_inference_steps: Optional[int] = 50,
         guidance_scale: Optional[float] = 7.5,
+        num_images_per_prompt: Optional[int] = 1,
         clip_guidance_scale: Optional[float] = 100,
         clip_prompt: Optional[Union[str, List[str]]] = None,
         num_cutouts: Optional[int] = 4,
@@ -203,6 +204,8 @@ def __call__(
             return_tensors="pt",
         )
         text_embeddings = self.text_encoder(text_input.input_ids.to(self.device))[0]
+        # duplicate text embeddings for each generation per prompt
+        text_embeddings = text_embeddings.repeat_interleave(num_images_per_prompt, dim=0)
 
         if clip_guidance_scale > 0:
             if clip_prompt is not None:
@@ -217,6 +220,8 @@ def __call__(
                 clip_text_input = text_input.input_ids.to(self.device)
             text_embeddings_clip = self.clip_model.get_text_features(clip_text_input)
             text_embeddings_clip = text_embeddings_clip / text_embeddings_clip.norm(p=2, dim=-1, keepdim=True)
+            # duplicate text embeddings clip for each generation per prompt
+            text_embeddings_clip = text_embeddings_clip.repeat_interleave(num_images_per_prompt, dim=0)
 
         # here `guidance_scale` is defined analog to the guidance weight `w` of equation (2)
         # of the Imagen paper: https://arxiv.org/pdf/2205.11487.pdf . `guidance_scale = 1`
@@ -225,10 +230,10 @@ def __call__(
         # get unconditional embeddings for classifier free guidance
         if do_classifier_free_guidance:
             max_length = text_input.input_ids.shape[-1]
-            uncond_input = self.tokenizer(
-                [""] * batch_size, padding="max_length", max_length=max_length, return_tensors="pt"
-            )
+            uncond_input = self.tokenizer([""], padding="max_length", max_length=max_length, return_tensors="pt")
             uncond_embeddings = self.text_encoder(uncond_input.input_ids.to(self.device))[0]
+            # duplicate unconditional embeddings for each generation per prompt
+            uncond_embeddings = uncond_embeddings.repeat_interleave(num_images_per_prompt, dim=0)
 
             # For classifier free guidance, we need to do two forward passes.
             # Here we concatenate the unconditional and text embeddings into a single batch
@@ -240,18 +245,20 @@ def __call__(
         # Unlike in other pipelines, latents need to be generated in the target device
         # for 1-to-1 results reproducibility with the CompVis implementation.
         # However this currently doesn't work in `mps`.
-        latents_device = "cpu" if self.device.type == "mps" else self.device
-        latents_shape = (batch_size, self.unet.in_channels, height // 8, width // 8)
+        latents_shape = (batch_size * num_images_per_prompt, self.unet.in_channels, height // 8, width // 8)
+        latents_dtype = text_embeddings.dtype
         if latents is None:
-            latents = torch.randn(
-                latents_shape,
-                generator=generator,
-                device=latents_device,
-            )
+            if self.device.type == "mps":
+                # randn does not exist on mps
+                latents = torch.randn(latents_shape, generator=generator, device="cpu", dtype=latents_dtype).to(
+                    self.device
+                )
+            else:
+                latents = torch.randn(latents_shape, generator=generator, device=self.device, dtype=latents_dtype)
         else:
             if latents.shape != latents_shape:
                 raise ValueError(f"Unexpected latents shape, got {latents.shape}, expected {latents_shape}")
-        latents = latents.to(self.device)
+            latents = latents.to(self.device)
 
         # set timesteps
         accepts_offset = "offset" in set(inspect.signature(self.scheduler.set_timesteps).parameters.keys())
@@ -261,17 +268,17 @@ def __call__(
 
         self.scheduler.set_timesteps(num_inference_steps, **extra_set_kwargs)
 
-        # if we use LMSDiscreteScheduler, let's make sure latents are multiplied by sigmas
-        if isinstance(self.scheduler, LMSDiscreteScheduler):
-            latents = latents * self.scheduler.sigmas[0]
+        # Some schedulers like PNDM have timesteps as arrays
+        # It's more optimized to move all timesteps to correct device beforehand
+        timesteps_tensor = self.scheduler.timesteps.to(self.device)
 
-        for i, t in enumerate(self.progress_bar(self.scheduler.timesteps)):
+        # scale the initial noise by the standard deviation required by the scheduler
+        latents = latents * self.scheduler.init_noise_sigma
+
+        for i, t in enumerate(self.progress_bar(timesteps_tensor)):
             # expand the latents if we are doing classifier free guidance
             latent_model_input = torch.cat([latents] * 2) if do_classifier_free_guidance else latents
-            if isinstance(self.scheduler, LMSDiscreteScheduler):
-                sigma = self.scheduler.sigmas[i]
-                # the model input needs to be scaled to match the continuous ODE formulation in K-LMS
-                latent_model_input = latent_model_input / ((sigma**2 + 1) ** 0.5)
+            latent_model_input = self.scheduler.scale_model_input(latent_model_input, t)
 
             # predict the noise residual
             noise_pred = self.unet(latent_model_input, t, encoder_hidden_states=text_embeddings).sample
@@ -299,10 +306,7 @@ def __call__(
                 )
 
             # compute the previous noisy sample x_t -> x_t-1
-            if isinstance(self.scheduler, LMSDiscreteScheduler):
-                latents = self.scheduler.step(noise_pred, i, latents).prev_sample
-            else:
-                latents = self.scheduler.step(noise_pred, t, latents).prev_sample
+            latents = self.scheduler.step(noise_pred, t, latents).prev_sample
 
         # scale and decode the image latents with vae
         latents = 1 / 0.18215 * latents