[bugfix] reduce float value error when adding noise (#9004)

* Update train_controlnet.py

reduce float value error for bfloat16

* Update train_controlnet_sdxl.py

* style

---------
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
Co-authored-by: yiyixuxu <yixu310@gmail.com>

examples/controlnet/train_controlnet.py

@@ -1048,7 +1048,9 @@ def main(args):
 
                 # Add noise to the latents according to the noise magnitude at each timestep
                 # (this is the forward diffusion process)
-                noisy_latents = noise_scheduler.add_noise(latents, noise, timesteps)
+                noisy_latents = noise_scheduler.add_noise(latents.float(), noise.float(), timesteps).to(
+                    dtype=weight_dtype
+                )
 
                 # Get the text embedding for conditioning
                 encoder_hidden_states = text_encoder(batch["input_ids"], return_dict=False)[0]

examples/controlnet/train_controlnet_sdxl.py

@@ -1210,7 +1210,9 @@ def main(args):
 
                 # Add noise to the latents according to the noise magnitude at each timestep
                 # (this is the forward diffusion process)
-                noisy_latents = noise_scheduler.add_noise(latents, noise, timesteps)
+                noisy_latents = noise_scheduler.add_noise(latents.float(), noise.float(), timesteps).to(
+                    dtype=weight_dtype
+                )
 
                 # ControlNet conditioning.
                 controlnet_image = batch["conditioning_pixel_values"].to(dtype=weight_dtype)