Los Alamos Chess

Original Article ↗ Hacker News Discussion ↗

Chess variant design & rules

  • Los Alamos chess removes bishops entirely and forbids promotion to bishops to avoid implementing extra piece logic on a highly constrained machine.
  • Retaining knights is defended: they generate fewer moves on average than bishops, especially on a small board, reducing branching factor while preserving interesting tactics.
  • Queens stay in; in one historical game the human played without a queen to handicap in favor of the computer.
  • Smaller boards and reduced pieces are seen as making games faster, easier to pick up, and still strategically rich.

Computational limits & solving complexity

  • Thread debate on whether the variant could be “solved”:
    • Full tablebases beyond 7 pieces in normal chess are already enormous; extending that logic suggests 24-piece Los Alamos chess is still intractable for complete tablebases.
    • Others note that “weak solving” (proving the game-theoretic value from the starting position) is more feasible, citing a 5×5 mini-chess that has been weakly solved without tablebases.
  • Branching factor, board size, and reduced rules (no castling, en passant, double pawn push) significantly cut search space, but not enough for full perfect-play databases.

Historical computing & naming

  • MANIAC’s 20-minute move times prompt reflection on how hard early coding and debugging were (e.g., tracing programs via card layouts on the floor).
  • A long technical correction distinguishes slow relay machines from much faster vacuum-tube computers, arguing:
    • Tube-based machines already did tens of thousands of operations per second.
    • Core memory latency, not tube speed, was often the bottleneck.
    • Architectural advances and miniaturization, more than raw transistor speed, drove the jump from kiloflops to today’s tera/petaflops.
  • Nostalgic discussion of old machine names (MANIAC, Colossus, etc.) versus modern “corporate” names.

Other games and variants

  • Multiple recommendations for short, chess-adjacent modern games, especially Onitama (5×5, move cards), plus mentions of Hive and Santorini.
  • Link to an online Los Alamos chess implementation; noted bug where pawns incorrectly promote to queens.

Sudoku-variant naming analogy

  • Lively side debate compares “sudoku variants” with chess variants:
    • Some dislike puzzles marketed as standard sudoku that rely on extra, sometimes arbitrary rules optimized for spectacle or computer search.
    • Others argue variants are legitimate extensions, analogous to chess families; they explore new constraint interactions and can still feel like “the same” logical game.
    • Disagreement over naming: whether such puzzles should still be called sudoku or something entirely different.

Miscellaneous observations

  • Clarifications that Los Alamos chess was not literally the first time a machine beat a human in a chess-like setting; earlier special-purpose automata existed.
  • Casual players often don’t know en passant; it’s a frequent source of confusion and online memes.
  • Several commenters jokingly expected a nuclear-themed ruleset from the name and sketch out hypothetical “atomic” mechanics involving piece decay or pawn “launches.”