Could not reproduce results for generate_synthia_label.py and the use of its result

I ran generate_synthia_label.py with both default settings (nproc=16) and nproc=1, but got output files varing greatly in size. Specifically, the file synthia_label_info.p you provided is around 1322KB, while my results are 458KB for nproc=16 and 1157KB for nproc=1. I am wondering what to blame for such a big difference.
Besides, would you be so kind to tell me about the functionality of such a step, as well as the performance boost of it?

Start with generate_synthia_label.py and reproduce the reported runs using nproc=16 and nproc=1. Inspect how synthia_label_info.p is produced and used; the issue is resolved when the output-size discrepancy, the step's functionality, and its performance effect are explained.

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