Ubodt.txt is extremely large

[tlian-lainie]

Describe the bug
Hi, Can. Thanks for providing a good open-source algorithm for map matching. I am using the algorithm to match Taxi GPS with roads, while encountered some problems when using the full dataset.
When I ran "fmm_example.ipynb" (in this folder: ../example/notebook) using my own dataset:

1. Road network reconstructed based on your standard with 70884 nodes and 126217 edges
2. GPS trajectory: 3553 points organized in a LineString of one vehicle.
   I found the ubodt.txt generated by this line: status = ubodt_gen.generate_ubodt("../data/test_data/ubodt.txt", 4, binary=False, use_omp=True) is extremely large (~136GB, have run for several hours and still running). It seems that something went wrong, but I failed to identify the error. Could you please give me some suggestions? Many thanks.

Screenshots
The code line with problem:

The structure of my road network:

The structure of my GPS trajectory:

[cyang-kth]

If your data is in unit of lat, lng, the delta of 4 in ubodt is 400km, you should try 3km if possible, which should be 0.03 degree in your case.

[cyang-kth]

Check this note #138 (comment)

[tlian-lainie]

Thanks a lot for your prompt feedback!! It worked now!! Thanks!