auto compute the training FPS by avg elapsed time

benchmark/paddle/image/run_mkldnn_train.sh

@@ -28,6 +28,10 @@ function train() {
     --test_period=100 \
     --config_args=$args \
     2>&1 | tee ${log} 
+
+  avg_time=`tail ${log} -n 1 | awk -F ' ' '{print $8}' | sed 's/avg=//'`
+  fps=`awk 'BEGIN{printf "%.2f",('$bs' / '$avg_time' * 1000)}'`
+  echo "FPS: $fps images/sec" 2>&1 | tee -a ${log}
 }
 
 if [ ! -f "train.list" ]; then