Tune the gaps and bridges for TG14.
Support multithreaded distro optimization.
Switch the Dijkstra to a heap-based version; about 60% faster in a quick test.

Depends a lot on the distro placement, though.
Find switch-to-distro map in one go, instead of linear search. Saves maybe 10%.
When searching for optimal distro placement, only log when we actually find a new best one.
More consistent distro numbering.
Drop all the logging stuff if we only care about cost.
Tiny cleanup.
Somewhat more efficient (~10%) priority queue.
Disable the node names by default; they take a tiny bit of time.