ACIQ bug fixes

* Return both min and max clip value in the symmetric case
* Correct delta from mean in asymmetric + half_range case

distiller/quantization/q_utils.py

@@ -230,7 +230,9 @@ class AciqSymmetricClipper(AciqClipper):
             mean = torch.tensor(t['mean'])
         else:
             mean = t.mean()
-        return torch.abs(mean) + alpha
+
+        clip_val = torch.abs(mean) + alpha
+        return -clip_val, clip_val
 
 
 class AciqAsymmetricClipper(AciqClipper):
@@ -249,8 +251,8 @@ class AciqAsymmetricClipper(AciqClipper):
         else:
             alpha = AciqClipper.get_alpha_gauss(t, across_dim, self.num_bits, half_range=half_range)
         min_val = torch.max(min_val, mean - alpha)
-
-        return min_val, min_val + 2 * alpha
+        delta = alpha if half_range else 2 * alpha
+        return min_val, min_val + delta
 
 
 def get_quantized_range(num_bits, signed=True):