Function ithFile

src/data/common.cc:13–17

DECLARE_bool(verbose);

DataConfig ithFile(const DataConfig& conf, int i, const string& suffix) {
  CHECK_GE(i, 0); CHECK_LT(i, conf.file_size());
  auto f = conf; f.clear_file(); f.add_file(conf.file(i) + suffix);
  return f;
}

MatrixInfo readMatrixInfo(
    const ExampleInfo& info, int slot_id, int sizeof_idx, int sizeof_val) {