Add history_len option to DelayedScalingRecipe

Summary: Add init function in DelayedScalingRecipe and history_len option.

Reviewed By: drisspg

Differential Revision: D52918526

fbshipit-source-id: b92df361a7b5b3507008b2ea7d8bb2d757e8aecb

Author: summerdengfb

float8_experimental/float8_linear.py

@@ -109,11 +109,18 @@ def backward(ctx, go):
 @dataclasses.dataclass
 class DelayedScalingRecipe:
     # Controls the history length of amax buffers
-    history_len = 16
+    history_len: int
 
     # Controls the way to calculate current scale from amax history
     # TODO(future): add other functions as needed, hardcoded or user defined
-    scale_fn_name = "max"
+    scale_fn_name: str
+
+    def __init__(self, history_len: int = 16, scale_fn_name: str = "max"):
+        self.history_len = history_len
+        self.scale_fn_name = scale_fn_name
+        assert (
+            self.scale_fn_name == "max"
+        ), f"{self.scale_fn_name} is not implemented yet. Only max is supported for now."
 
 
 class Float8LinearMixin(object):