[examples] fix mixed_precision arg (#1359)

* use accelerator to check mixed_precision

* default `mixed_precision` to `None`

* pass mixed_precision to accelerate launch

examples/dreambooth/README.md

@@ -141,7 +141,7 @@ export INSTANCE_DIR="path-to-instance-images"
 export CLASS_DIR="path-to-class-images"
 export OUTPUT_DIR="path-to-save-model"
 
-accelerate launch train_dreambooth.py \
+accelerate launch --mixed_precision="fp16" train_dreambooth.py \
   --pretrained_model_name_or_path=$MODEL_NAME \
   --instance_data_dir=$INSTANCE_DIR \
   --class_data_dir=$CLASS_DIR \
@@ -157,8 +157,7 @@ accelerate launch train_dreambooth.py \
   --lr_scheduler="constant" \
   --lr_warmup_steps=0 \
   --num_class_images=200 \
-  --max_train_steps=800 \
-  --mixed_precision=fp16
+  --max_train_steps=800
 ```
 
 ### Fine-tune text encoder with the UNet.

examples/dreambooth/train_dreambooth.py

@@ -187,12 +187,12 @@ def parse_args(input_args=None):
     parser.add_argument(
         "--mixed_precision",
         type=str,
-        default="no",
+        default=None,
         choices=["no", "fp16", "bf16"],
         help=(
-            "Whether to use mixed precision. Choose"
-            "between fp16 and bf16 (bfloat16). Bf16 requires PyTorch >= 1.10."
-            "and an Nvidia Ampere GPU."
+            "Whether to use mixed precision. Choose between fp16 and bf16 (bfloat16). Bf16 requires PyTorch >="
+            " 1.10.and an Nvidia Ampere GPU.  Default to the value of accelerate config of the current system or the"
+            " flag passed with the `accelerate.launch` command. Use this argument to override the accelerate config."
         ),
     )
     parser.add_argument("--local_rank", type=int, default=-1, help="For distributed training: local_rank")
@@ -538,9 +538,9 @@ def main(args):
         )
 
     weight_dtype = torch.float32
-    if args.mixed_precision == "fp16":
+    if accelerator.mixed_precision == "fp16":
         weight_dtype = torch.float16
-    elif args.mixed_precision == "bf16":
+    elif accelerator.mixed_precision == "bf16":
         weight_dtype = torch.bfloat16
 
     # Move text_encode and vae to gpu.

examples/text_to_image/README.md

@@ -46,7 +46,7 @@ With `gradient_checkpointing` and `mixed_precision` it should be possible to fin
 export MODEL_NAME="CompVis/stable-diffusion-v1-4"
 export dataset_name="lambdalabs/pokemon-blip-captions"
 
-accelerate launch train_text_to_image.py \
+accelerate launch --mixed_precision="fp16"  train_text_to_image.py \
   --pretrained_model_name_or_path=$MODEL_NAME \
   --dataset_name=$dataset_name \
   --use_ema \
@@ -54,7 +54,6 @@ accelerate launch train_text_to_image.py \
   --train_batch_size=1 \
   --gradient_accumulation_steps=4 \
   --gradient_checkpointing \
-  --mixed_precision="fp16" \
   --max_train_steps=15000 \
   --learning_rate=1e-05 \
   --max_grad_norm=1 \
@@ -70,7 +69,7 @@ If you wish to use custom loading logic, you should modify the script, we have l
 export MODEL_NAME="CompVis/stable-diffusion-v1-4"
 export TRAIN_DIR="path_to_your_dataset"
 
-accelerate launch train_text_to_image.py \
+accelerate launch --mixed_precision="fp16" train_text_to_image.py \
   --pretrained_model_name_or_path=$MODEL_NAME \
   --train_data_dir=$TRAIN_DIR \
   --use_ema \
@@ -78,7 +77,6 @@ accelerate launch train_text_to_image.py \
   --train_batch_size=1 \
   --gradient_accumulation_steps=4 \
   --gradient_checkpointing \
-  --mixed_precision="fp16" \
   --max_train_steps=15000 \
   --learning_rate=1e-05 \
   --max_grad_norm=1 \

examples/text_to_image/train_text_to_image.py

@@ -186,12 +186,12 @@ def parse_args():
     parser.add_argument(
         "--mixed_precision",
         type=str,
-        default="no",
+        default=None,
         choices=["no", "fp16", "bf16"],
         help=(
-            "Whether to use mixed precision. Choose"
-            "between fp16 and bf16 (bfloat16). Bf16 requires PyTorch >= 1.10."
-            "and an Nvidia Ampere GPU."
+            "Whether to use mixed precision. Choose between fp16 and bf16 (bfloat16). Bf16 requires PyTorch >="
+            " 1.10.and an Nvidia Ampere GPU.  Default to the value of accelerate config of the current system or the"
+            " flag passed with the `accelerate.launch` command. Use this argument to override the accelerate config."
         ),
     )
     parser.add_argument(
@@ -496,9 +496,9 @@ def main():
     )
 
     weight_dtype = torch.float32
-    if args.mixed_precision == "fp16":
+    if accelerator.mixed_precision == "fp16":
         weight_dtype = torch.float16
-    elif args.mixed_precision == "bf16":
+    elif accelerator.mixed_precision == "bf16":
         weight_dtype = torch.bfloat16
 
     # Move text_encode and vae to gpu.