text:                 fprintf(stderr, "%4d: features dim: %lu x %lu - [%.8g, %.8g, ...] label dim: %lu x %lu - [%d, %d, ...]\n", i++, (unsigned long)features.GetNumRows(), (unsigned long)features.GetNumCols(), features(0, 0), features(0, 1), (unsigned long)labels.GetNumRows(), (unsigned long)labels.GetNumCols(), (int) labels(0, 0), (int) labels(0, 1));
  