add some useful decorators

Author: ZhiyuanChen

src/accelerate/decorator.py

@@ -0,0 +1,23 @@
+from functools import wraps
+
+
+def on_main_process(func):
+    """
+    Run func on main process only
+    """
+    @wraps(func)
+    def wrapper(self, *args, **kwargs):
+        if self.is_main_process or not self.use_distributed:
+            return func(self, *args, **kwargs)
+    return wrapper
+
+
+def on_local_main_process(func):
+    """
+    Run func on local main process only
+    """
+    @wraps(func)
+    def wrapper(self, *args, **kwargs):
+        if self.is_local_main_process or not self.use_distributed:
+            return func(self, *args, **kwargs)
+    return wrapper