BDD compose can perform many duplicate operations

[tim-hoffman]

I'm wondering why the implementation of compose(int,int,int) in BDDImpl does not utilize caching like many of the other operations do. Without caching, the operation performs very poorly on large BDD instances. Is there some specific challenge related to multithreading or was it just an oversight?

[spoto]

This operation was not extensively used in our applications, hence we never put a cache here. However, a cache can be easily added here as for other operations. We will do it soon and publish an updated version of the library.