fix(mge/quantization): replace `_reset` with "=" in observer

GitOrigin-RevId: ed6af9b98d1f68811a78f44d531c52b60339fbbe

imperative/python/megengine/quantization/observer.py

@@ -153,11 +153,11 @@ class ExponentialMovingAverageObserver(MinMaxObserver):
         **kwargs
     ):
         super().__init__(mode, eps, dtype, narrow_range, **kwargs)
-        self.momentum = Tensor(momentum)
+        self.momentum = Tensor(momentum, dtype="float32")
         self.runtime_momentum = Tensor(0.0)
 
     def set_momentum(self, momentum):
-        self.momentum._reset(momentum)
+        self.momentum = Tenosr(momentum, dtype="float32")
 
     def forward(self, x_orig):
         if self.enabled:
@@ -439,9 +439,9 @@ class HistogramObserver(MinMaxObserver):
                     self.bins,
                 )
 
-        self.histogram._reset(new_histogram)
-        self.min_val._reset(new_min)
-        self.max_val._reset(new_max)
+        self.histogram = Tensor(new_histogram, dtype="float32")
+        self.min_val = Tensor(new_min, dtype="float32")
+        self.max_val = Tensor(new_max, dtype="float32")
 
     def forward(self, x_orig):
         self.sideeffect_forward(x_orig)

imperative/python/test/unit/quantization/test_observer.py

@@ -8,6 +8,7 @@ import megengine.distributed as dist
 from megengine.distributed.helper import get_device_count_by_fork
 from megengine.quantization.observer import (
     ExponentialMovingAverageObserver,
+    HistogramObserver,
     MinMaxObserver,
     Observer,
     PassiveObserver,
@@ -44,6 +45,16 @@ def test_exponential_moving_average_observer():
     np.testing.assert_allclose(m.max_val.numpy(), expected_max)
 
 
+def test_histogram_observer():
+    x = np.random.rand(3, 3, 3, 3).astype("float32")
+    np_min, np_max = x.min(), x.max()
+    x = mge.tensor(x)
+    m = HistogramObserver()
+    m(x)
+    np.testing.assert_allclose(m.min_val.numpy(), np_min)
+    np.testing.assert_allclose(m.max_val.numpy(), np_max)
+
+
 def test_passive_observer():
     q_dict = {"scale": mge.tensor(1.0)}
     m = PassiveObserver(q_dict, "qint8")