White 17 vs Black 823

The two setups

White: setup #17 B N Q B N R K R

King on the g-file, rooks on f, h, queen on the c-file; one bishop starts in a corner; the knights start on central files. The king already stands on a castled square, so one of the castlings moves only the rook. In ordinary symmetric play setup 17 gives White +0.20 (Morozov Balance Index, 400M nodes).

Black: setup #823 R K B N Q R N B

King on the b-file, rooks on a, f, queen on the e-file; one bishop starts in a corner; the knights start on central files. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 823 gives White -0.05 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation is exactly 0.00 each time, reaching search depth 53.

Admission rule: |cp| ≤ 5 at four budgets up to 4 billion nodes, no one-sided drift along the ladder, and confirmation by two independent engines — Berserk and Lc0 — each below its own median on symmetric positions. The same corridor is required at every deeper budget (8 G, 16 G) at which the pair has been evaluated.

The shallow rungs wandered between -10 and +17 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 17 gives White +0.20 and setup 823 gives White -0.05: with both sides on the same rank the first move is worth something. In this pair Black's own setup absorbs that edge completely.

White is not forced into a single path: the best first move is d4, and 3 first moves are within 10 cp of it.

Along the engine's main line (14 moves) the evaluation stayed within ±18 cp the whole way: the balance holds as the pieces come out, not only on move one.

Engine self-play agrees: 10 games, White won 0, drawn 10, Black won 0 (White scored 50.0%).

Verification ladder

Nine independent searches of the starting position, each with a larger node budget. Evaluation in centipawns from White's point of view.

Deep verification

The search ladder reaches 1.6 billion nodes; admission needs a 4-billion rung and two further engines on top of that. Beyond even that, every pair was re-checked at budgets up to ten times larger and in thousands of self-play games. This section shows what each check returned for this pair.

This pair stays within the ±5 cp corridor up to 4 000 000 000 nodes.

Independent engines, run on the same position:

• Berserk 14: +8
• Lc0 0.32.1: +1

Independent confirmations: 3 of 3. An engine counts as confirming when its reading of the pair is closer to equality than its own reading of a typical symmetric Chess960 position (+10 for Berserk, +18 for Lc0). Where only one engine confirms, the pair is balanced according to that engine alone, and this page says so.

Own weight of each setup, measured against the classical array: White +73, Black +106, difference -33. A balanced pair needs White's setup to be weaker by about the price of the first move.

Extended self-play: 10 games, 0 White wins, 10 draws, 0 Black wins, White scored 50.0%.

Best first moves

The 3 best first moves for White, searched together at 400 000 000 nodes.

Main-line play-out

14 moves, 5 000 000 nodes per half-move. Largest |evaluation| 18 cp, mean 4.3 cp, final 0 cp.

Engine self-play

10 games at 500 000 nodes per move: White won 0, drawn 10, Black won 0 — White scored 50.0%. Average length 41.2 moves.

1. d4 g6 2. e3 e5 3. c4 exd4 4. b3 dxe3 5. Bxh8 e2 6. Bxe2 Qxe2 7. Bb2 Qh5 8. Nc3 b6 9. h4 Bb7 10. f3 d6 11. Nd5 Qf5 12. Nc2 Bxd5 13. Ne3 Qf4 14. Nxd5 Qxc1 15. Rxc1 Ne6 16. Kf2 a5 17. h5 g5 18. Rcd1 Kc8 19. Rhe1 Kd7 20. a3 Rfe8 21. g4 Reb8 22. b4 axb4 23. axb4 Ra4 24. Re4 Rf8 25. Rde1 b5 26. cxb5 Rb8 27. Nc3 Raa8 28. h6 Rb7 29. Bc1 Ra1 30. Bd2 Ra3 31. Rc4 Rb3 32. Bc1 Rb8 33. Rd1 Nf6 34. Ke2 Ke8 35. Be3 Nd7 36. Nd5 Rb2+ 37. Kf1 Ne5 38. Rc3 Rxb5 39. Nxc7+ Nxc7 40. Rxc7 R5xb4 41. Bxg5 Nxf3 42. Rc8+ Kd7 43. Rd8+ Kc7

1. b3 a5 2. d4 h6 3. e4 d6 4. Nd3 Nc6 5. Re1 g5 6. e5 Bf5 7. Na3 Nb4 8. Qd2 Nxd3 9. cxd3 e6 10. exd6 cxd6 11. h4 gxh4 12. Rxh4 Bf6 13. Rh5 Qd8 14. Bc3 Ne7 15. Nc4 Nd5 16. Bxa5 Bg5 17. Bxd8 Bxd2 18. Nxd2 Rxa2 19. Bh4 Rxd2 20. Bf3 Bg6 21. Rxd5 exd5 22. Be7 Rc8 23. Bxd6+ Ka7 24. Bc5+ Rxc5 25. dxc5 Rxd3 26. Re7 Rxb3 27. c6 Rb1+ 28. Kh2 Kb6 29. cxb7 Kc6 30. Re5 Rxb7 31. Rxd5 Rb4 32. Rd4+ Kc5 33. Rxb4 Kxb4 34. Kg3 Kc5 35. Kf4 Kd6 36. Be4 Ke6 37. Bxg6 fxg6 38. g4 Kd5 39. Ke3 h5 40. gxh5 gxh5

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 17 / 823 in the app's encyclopedia, then choose how to play.

• Local game — two players on one device, with a clock.
• With a mentor — a clearly labelled training bot with hints, at your level.
• Challenge a friend — an online game by link; both players get the same pair, colours swap on rematch.

Play this pair against the computer, right here Play a friend

FEN (Shredder, castling rights by rook files): rkbnqrnb/pppppppp/8/8/8/8/PPPPPPPP/BNQBNRKR w FHaf - 0 1

Mirror twin: White 939 vs Black 130 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 130.