changed language of cautionary note

theano/sandbox/cuda/basic_ops.py

@@ -514,10 +514,9 @@ class GpuCAReduce(GpuOp):
     scal.Add instances yet.
 
     Important note: if you implement new cases for this op, be sure to
-    benchmark them and make sure that the local_gpu_careduce op should
-    really replace CAReduce with GpuCAReduce for these cases. GPUs are
-    not especially well-suited to reduction operations so it is quite
-    possible that the GPU might be slower for some cases.
+    benchmark them and make sure that they actually result in a speedup.
+    GPUs are not especially well-suited to reduction operations so it is
+    quite possible that the GPU might be slower for some cases.
 
     """