Use custom hash for maps and tuples to improve ordering#15398
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| @map_leaf_hash_range 1 <<< 28 | ||
| @tuple_leaf_hash_range 1 <<< 28 |
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I believe phash2 is 32bit so maybe we want to use 33?
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Apparently the default is to 27, so we are good!
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Map literals with a smaller hash get ordered higher in the BDD. If we use a negative hash for the
:closedmaps, then they will appear higher in BDDs and this will factor them (instead of having it multiplied on every leaf). We can also add a weight for the number of fields, so that more fields appear higher than less fields.The same can be done for tuples as well.
The performance boost appears when using plain bdd operations (e.g. Livebook typechecking goes from 750ms to the usual ~280ms).