Peter McGavin's own C backtracker, the fastest raw solver the community has measured. Fetched from the mailing list, built on an M1, and run on the real Eternity II. His code, his algorithm; run and written up here.
This section is Peter McGavin's own solver: the C backtracker he posted to the mailing list, which by the community's measurements is the fastest raw engine anyone has run. The algorithm and the code are his. What is added here is the running: fetched from source, built on one machine, and pointed at the real puzzle, with the numbers written up.