Adding HistogramObserver

src/sparseml/modifiers/quantization/utils/quantization_scheme.py

@@ -121,7 +121,7 @@ def get_observer(self) -> "torch.quantization.FakeQuantize":
 
     @validator("strategy")
     def validate_strategy(cls, value):
-        valid_scopes = ["tensor", "channel"]
+        valid_scopes = ["tensor", "channel", "histogram"]
         if value not in valid_scopes:
             raise ValueError(f"`strategy` must be one of {valid_scopes}, got {value}")
         return value
@@ -307,6 +307,14 @@ def get_observer(
             qscheme=qscheme,
             reduce_range=reduce_range,
         )
+    elif strategy == "histogram":
+        qscheme = torch.per_tensor_symmetric if symmetric else torch.per_tensor_affine
+        observer_cls = torch_quantization.HistogramObserver
+        observer_kwargs = dict(
+            dtype=dtype,
+            qscheme=qscheme,
+            reduce_range=reduce_range,
+        )
     else:  # default to tensor strategy
         qscheme = torch.per_tensor_symmetric if symmetric else torch.per_tensor_affine
         observer_cls = torch_quantization.MovingAverageMinMaxObserver