# Peter McGavin's engine

> 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.

- Canonical page (with interactive figures/demos): https://eternity2.dev/research/lab/experiments/peter-mcgavin/
- Updated: 2026-07-15

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This section is [Peter McGavin's](/research/people/peter-mcgavin) 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.

## Pages in this section

- [McGavin's C backtracker: the throughput story, built here](https://eternity2.dev/research/lab/experiments/peter-mcgavin/backtracker) — Peter McGavin's own C backtracker, the community's fastest: a 2007 optimization recipe compounded for two decades through generated code, lookup tables and counter tricks, then built on my M1 and pointed at the real 256-piece puzzle, where single core it drives past 200 of 256 pieces at ~109M placements/s.