[AUTOTVM] Fix measurement for CPU (#1956)

python/tvm/autotvm/measure/measure_methods.py

@@ -460,7 +460,11 @@ def run_through_rpc(measure_input, build_result,
         if ref_input:
             args = [nd.array(x, ctx=ctx) for x in ref_input]
         else:
+            # create empty arrays on the remote device and copy them once.
+            # This can avoid some memory issues that make the measurment results unreliable.
             args = [nd.empty(x[0], dtype=x[1], ctx=ctx) for x in build_result.arg_info]
+            args = [nd.array(x, ctx=ctx) for x in args]
+            ctx.sync()
 
         costs = time_f(*args).results
         if len(costs) > 2:  # remove largest and smallest value to reduce variance