fix sqrt

python/paddle/fluid/clip.py

@@ -280,7 +280,7 @@ class GradientClipByGlobalNorm(BaseGradientClipAttr):
         group_scale_name = self.group_name + "_scale"
         if group_scale_name not in self.context:
             group_norm_var = layers.sums(input=self.context[self.group_name])
-            layers.sqrt(x=group_norm_var, out=group_norm_var)
+            group_norm_var = layers.sqrt(x=group_norm_var)
             clip_var = self.context[self.group_name + "_clip"]
             group_scale_var = layers.elementwise_div(
                 x=clip_var,