# Joshua Blackwood's solver

> Joshua Blackwood's open-source C# solver, the one that found the standing 470 record. Built and run here as he published it, then with the five official clues pinned. His code, his algorithm; run and written up here.

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

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This section is [Joshua Blackwood's](/research/people/joshua-blackwood) own
solver: the open-source C# program that found the 470 that still stands. The
algorithm and the code are his, public on GitHub. What is added here is the
running: built as he published it, measured single core, and then tested against
the real five-clue puzzle to see what its speed is actually buying.

## Pages in this section

- [Blackwood's solver, decoded and run here](https://eternity2.dev/research/lab/experiments/joshua-blackwood/solver) — Joshua Blackwood's record backtracker, decoded through Jef Bucas's notes (a colour quota schedule and a late-game mismatch allowance, tuned near-optimally), then built and run on my M1: left as published it flies to 248 of 256 pieces ignoring the clues; pin the five official clues and the same engine stalls near 45.