Upon activating PoC v4 at 1:50 PM PST on December 2nd we soon realized that the calc_edge_prob had
become a performance bottleneck. In response, we changed the order of operations and switched from
using sets to lists so the calculation is less costly.
The changes are encapsulated in blockchain-core#303.
The beta deploy was done around 5:10 PM PST and will be deployed to GA shortly.