[chatgpt]add inference example
diff --git a/applications/ChatGPT/examples/README.md b/applications/ChatGPT/examples/README.md
index 5f9d8698d616..e5522f08770d 100644
--- a/applications/ChatGPT/examples/README.md
+++ b/applications/ChatGPT/examples/README.md
@@ -6,7 +6,21 @@
 pip install -r requirements.txt
 ```
 
-## Train with dummy prompt data
+## Train the reward model (Stage 2)
+We use [rm-static](https://huggingface.co/datasets/Dahoas/rm-static) as dataset to train our reward model. It is a dataset of chosen & rejected response of the same prompt.
+
+You can download the dataset from huggingface automatically.
+
+Use these code to train your reward model.
+
+```shell
+# Naive reward model training
+python train_reward_model.py --pretrain <your model path>
+# if to use LoRA
+python train_reward_model.py --pretrain <your model path> --lora_rank 16
+```
+
+## Train with dummy prompt data (Stage 3)
 
 This script supports 3 strategies:
 
@@ -33,7 +47,7 @@ torchrun --standalone --nproc_per_node=2 train_dummy.py --strategy ddp
 torchrun --standalone --nproc_per_node=2 train_dummy.py --strategy colossalai
 ```
 
-## Train with real prompt data
+## Train with real prompt data (Stage 3)
 
 We use [awesome-chatgpt-prompts](https://huggingface.co/datasets/fka/awesome-chatgpt-prompts) as example dataset. It is a small dataset with hundreds of prompts.
 
@@ -52,18 +66,11 @@ torchrun --standalone --nproc_per_node=2 train_prompts.py prompts.csv --strategy
 torchrun --standalone --nproc_per_node=2 train_prompts.py prompts.csv --strategy colossalai
 ```
 
-## Train the reward model
-We use [rm-static](https://huggingface.co/datasets/Dahoas/rm-static) as dataset to train our reward model. It is a dataset of chosen & rejected response of the same prompt.
-
-You can download the dataset from huggingface automatically.
-
-Use these code to train your reward model.
-
+## Inference example(After Stage3)
+We support naive inference demo after training.
 ```shell
-# Naive reward model training
-python train_reward_model.py --pretrain <your model path>
-# if to use LoRA
-python train_reward_model.py --pretrain <your model path> --lora_rank 16
+# inference
+python inference_actor.py --pretrain <your actor model path> --model <your model type>
 ```
 
 ## Support Model
@@ -91,8 +98,8 @@ python train_reward_model.py --pretrain <your model path> --lora_rank 16
 ### BLOOM
 - [x] [BLOOM-560m](https://huggingface.co/bigscience/bloom-560m)
 - [x] [BLOOM-1b1](https://huggingface.co/bigscience/bloom-1b1)
-- [ ] [BLOOM-3b](https://huggingface.co/bigscience/bloom-3b)
-- [ ] [BLOOM-7b](https://huggingface.co/bigscience/bloomz-7b1)
+- [x] [BLOOM-3b](https://huggingface.co/bigscience/bloom-3b)
+- [x] [BLOOM-7b](https://huggingface.co/bigscience/bloomz-7b1)
 - [ ] BLOOM-175b
 
 ### OPT
diff --git a/applications/ChatGPT/examples/inference.py b/applications/ChatGPT/examples/inference.py
new file mode 100644
index 000000000000..ba055d81fd15
--- /dev/null
+++ b/applications/ChatGPT/examples/inference.py
@@ -0,0 +1,52 @@
+import argparse
+import torch
+
+from chatgpt.nn import BLOOMActor, GPTActor, OPTActor
+from transformers import AutoTokenizer
+from transformers.models.gpt2.tokenization_gpt2 import GPT2Tokenizer
+
+
+def eval(args):
+    # configure model
+    if args.model == 'gpt2':
+        model = GPTActor(pretrained=args.pretrain).to(torch.cuda.current_device())
+    elif args.model == 'bloom':
+        model = BLOOMActor(pretrained=args.pretrain).to(torch.cuda.current_device())
+    elif args.model == 'opt':
+        model = OPTActor(pretrained=args.pretrain).to(torch.cuda.current_device())
+    else:
+        raise ValueError(f'Unsupported model "{args.model}"')
+
+    # configure tokenizer
+    if args.model == 'gpt2':
+        tokenizer = GPT2Tokenizer.from_pretrained('gpt2')
+        tokenizer.pad_token = tokenizer.eos_token
+    elif args.model == 'bloom':
+        tokenizer = AutoTokenizer.from_pretrained(args.pretrain)
+        tokenizer.pad_token = tokenizer.eos_token
+    elif args.model == 'opt':
+        tokenizer = AutoTokenizer.from_pretrained("facebook/opt-350m")
+    else:
+        raise ValueError(f'Unsupported model "{args.model}"')
+
+    model.eval()
+    input = args.input
+    input_ids = tokenizer.encode(input, return_tensors='pt').to(torch.cuda.current_device())
+    outputs = model.generate(input_ids,
+                             max_length=args.max_length,
+                             do_sample=True,
+                             top_k=50,
+                             top_p=0.95,
+                             num_return_sequences=1)
+    output = tokenizer.batch_decode(outputs[0], skip_special_tokens=True)
+    print(output)
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--model', default='gpt2', choices=['gpt2', 'bloom', 'opt'])
+    parser.add_argument('--pretrain', type=str, default=None)
+    parser.add_argument('--input', type=str, default='Q: How are you ? A:')
+    parser.add_argument('--max_length', type=int, default=100)
+    args = parser.parse_args()
+    eval(args)

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>
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fixed #2870 #2915 #


## 📝 What does this PR do?

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> if you have any plots/diagrams/screenshots/tables, please attach them here.
Add a demo of inference in Chatgpt/examples

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