[accelerator] init the accelerator module (#5129)

* [accelerator] init the accelerator module

* polish code

* polish code

* polish code

* polish code

colossalai/accelerator/cuda_accelerator.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+from typing import Union
+
+import torch
+
+from .base_accelerator import BaseAccelerator
+
+__all__ = ["CudaAccelerator"]
+
+
+class CudaAccelerator(BaseAccelerator):
+    """
+    Accelerator class for Nvidia CUDA devices.
+    """
+
+    def __init__(self):
+        super().__init__(name="cuda", communication_backend="nccl", is_synchronous=False)
+
+    # =======================
+    # device APIs
+    # =======================
+    def current_device(self) -> int:
+        """
+        Return the current device index.
+        """
+        return torch.cuda.current_device()
+
+    def set_device(self, device: Union[torch.device, int]) -> None:
+        """
+        Bind the current process to a device.
+        """
+        torch.cuda.set_device(device)
+
+    def get_device_name(self, device: Union[torch.device, int]) -> str:
+        """
+        Return the name of the device.
+        """
+        return torch.cuda.get_device_name(device)
+
+    def synchronize(self, device: Union[torch.device, int] = None):
+        """
+        Synchronize the current process.
+        """
+        torch.cuda.synchronize(device)
+
+    def is_available(self):
+        """
+        Check if the accelerator is available.
+        """
+        return torch.cuda.is_available()
+
+    def device_count(self):
+        """
+        Return the number of devices on the machine.
+        """
+        return torch.cuda.device_count()