[Inference] First PR for rebuild colossal-infer (#5143)

* add engine and scheduler

* add dirs

---------

Co-authored-by: CjhHa1 <cjh18671720497outlook.com>

colossalai/inference/core/engine.py

@@ -0,0 +1,73 @@
+from logging import Logger
+from typing import Optional
+
+from .request_handler import RequestHandler
+
+
+class InferEngine:
+    """
+    InferEngine is the core component for Inference.
+
+    It is responsible for launch the inference process, including:
+        - Initialize model and distributed training environment(if needed)
+        - Launch request_handler and corresponding kv cache manager
+        - Receive requests and generate texts.
+        - Log the generation process
+
+    Args:
+        colossal_config: We provide a unified config api for that wrapped all the configs. You can use it to replace the below configs.
+        model_config : The configuration for the model.
+        parallel_config: The configuration for parallelize model.
+        cache_config : Configuration for initialize and manage kv cache.
+        tokenizer (Tokenizer): The tokenizer to be used for inference.
+        use_logger (bool): Determine whether or not to log the generation process.
+    """
+
+    def __init__(
+        self,
+        model_config,
+        cache_config,
+        parallel_config,
+        tokenizer,
+        use_logger: bool = False,
+        colossal_config: Optional["ColossalInferConfig"] = None,
+    ) -> None:
+        assert colossal_config or (
+            model_config and cache_config and parallel_config
+        ), "Please provide colossal_config or model_config, cache_config, parallel_config"
+        if colossal_config:
+            model_config, cache_config, parallel_config = colossal_config
+
+        self.model_config = model_config
+        self.cache_config = cache_config
+        self.parallel_config = parallel_config
+        self._verify_config()
+
+        self._init_model()
+        self.request_handler = RequestHandler(cache_config)
+        if use_logger:
+            self.logger = Logger()
+
+    def _init_model(self):
+        """
+        Initialize model and distributed training environment(if needed).
+        May need to provide two different initialization methods:
+            1. 用户自定义(from local path)
+            2. 从checkpoint加载(hugging face)
+        """
+
+    def _verify_config(self):
+        """
+        Verify the configuration to avoid potential bugs.
+        """
+
+    def generate(self):
+        pass
+
+    def step(self):
+        """
+        In each step, do the follows:
+            1. Run request_handler to update the kv cache and running input_ids
+            2. Run model to generate the next token
+            3. Check whether there is finied request and decode
+        """

colossalai/inference/core/request_handler.py

@@ -0,0 +1,10 @@
+class RequestHandler:
+    def __init__(self, cache_config) -> None:
+        self.cache_config = cache_config
+        self._init_cache()
+
+    def _init_cache(self):
+        pass
+
+    def schedule(self, request):
+        pass