fix potential bug in quantize device (#3212)

Co-authored-by: yuanxiulong <yuanxiulong@bytedance.com>

nni/algorithms/compression/pytorch/quantization/quantizers.py

@@ -85,16 +85,10 @@ def update_quantization_param(bits, rmin, rmax):
     # extend the [min, max] interval to ensure that it contains 0.
     # Otherwise, we would not meet the requirement that 0 be an exactly
     # representable value.
-    if rmin.is_cuda:
-        rmin = torch.min(rmin, torch.Tensor([0]).cuda())
-        rmax = torch.max(rmax, torch.Tensor([0]).cuda())
-        qmin = torch.Tensor([0]).cuda()
-        qmax = torch.Tensor([(1 << bits) - 1]).cuda()
-    else:
-        rmin = torch.min(rmin, torch.Tensor([0]))
-        rmax = torch.max(rmax, torch.Tensor([0]))
-        qmin = torch.Tensor([0])
-        qmax = torch.Tensor([(1 << bits) - 1])
+    rmin = torch.min(rmin, torch.Tensor([0]).to(rmin.device))
+    rmax = torch.max(rmax, torch.Tensor([0]).to(rmin.device))
+    qmin = torch.Tensor([0]).to(rmin.device)
+    qmax = torch.Tensor([(1 << bits) - 1]).to(rmin.device)
 
     # First determine the scale.
     scale = (rmax - rmin) / (qmax - qmin)
@@ -103,7 +97,6 @@ def update_quantization_param(bits, rmin, rmax):
     initial_zero_point = qmin - rmin / scale
 
     # Now we need to nudge the zero point to be an integer
-    nudged_zero_point = 0
     if initial_zero_point < qmin:
         nudged_zero_point = qmin
     elif initial_zero_point > qmax:
@@ -199,10 +192,8 @@ class QAT_Quantizer(Quantizer):
         -------
         Tensor
         """
-        if real_val.is_cuda:
-            op.zero_point = op.zero_point.cuda()
-            op.scale = op.scale.cuda()
-
+        op.zero_point = op.zero_point.to(real_val.device)
+        op.scale = op.scale.to(real_val.device)
         transformed_val = op.zero_point + real_val / op.scale
         qmin = 0
         qmax = (1 << bits) - 1