loss_scaler.py: patching loss scaler for compatibility with current pytorch

Author: Rafael Valle

loss_scaler.py

@@ -51,11 +51,10 @@ def has_overflow(self, params):
 
     # `x` is a torch.Tensor
     def _has_inf_or_nan(x):
-        inf_count = torch.sum(x.abs() == float('inf'))
-        if inf_count > 0:
+        cpu_sum = float(x.float().sum())
+        if cpu_sum == float('inf') or cpu_sum == -float('inf') or cpu_sum != cpu_sum:
             return True
-        nan_count = torch.sum(x != x)
-        return nan_count > 0
+        return False
 
     # `overflow` is boolean indicating whether we overflowed in gradient
     def update_scale(self, overflow):