How CpcSketch's CompressionData gets generated?

In code comment, I saw:

```
~/ocaml-4.03.0/bin/ocamlopt -o generateHuffmanCodes columnProbabilities.ml generateHuffmanCodes.ml
./generateHuffmanCodes > raw-encoding-tables.c
```

But I can't find the source of (`columnProbabilities.ml generateHuffmanCodes.ml`) anywhere.