message: remove the ns of time
diff: @@ -276,7 +276,7 @@ void spmv_system(const char *format_name,
  auto toc = std::chrono::system_clock::now();
  time += std::chrono::duration_cast<duration_type>(toc - tic);
  }
  - add_or_set_member(test_case[format_name], "time(ns)",
  + add_or_set_member(test_case[format_name], "time",
  static_cast<double>(time.count()) / run_iter, allocator);
  // compute and write benchmark data
  @@ -358,11 +358,11 @@ int main(int argc, char *argv[])
  if (best_format == "none") {
  best_format = format_name;
  best_performace =
  - test_case[format_name.c_str()]["time(ns)"]
  + test_case[format_name.c_str()]["time"]
  .GetDouble();
  } else {
  auto performance =
  - test_case[format_name.c_str()]["time(ns)"]
  + test_case[format_name.c_str()]["time"]
  .GetDouble();
  if (performance < best_performace) {
  best_format = format_name;
  