White 83 vs Black 919

The two setups

White: setup #83 B N N R K R Q B

King on the e-file, rooks on d, f, queen on the g-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 83 gives White +0.29 (Morozov Balance Index, 400M nodes).

Black: setup #919 R K B R Q N N B

King on the b-file, rooks on a, d, 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 919 gives White +0.22 (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 54.

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 agreed early: from 100 thousand to 128 million nodes the evaluation never left ±8 cp.

For comparison, in symmetric play setup 83 gives White +0.29 and setup 919 gives White +0.22: 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 2 first moves are within 10 cp of it.

Along the engine's main line (17 moves) the evaluation stayed within ±16 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: 0
• 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 +95, Black +132, difference -37. 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

17 moves, 5 000 000 nodes per half-move. Largest |evaluation| 16 cp, mean 1.6 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 41.0 moves.

1. b4 e5 2. Nb3 d5 3. g3 a5 4. bxa5 f5 5. f4 e4 6. d3 Ne7 7. g4 Ra6 8. O-O-O Nd7 9. gxf5 Nxf5 10. dxe4 dxe4 11. Rd5 Nd6 12. Nc3 g6 13. Nxe4 Bxa1 14. Nxd6 Rxd6 15. Rxd6 cxd6 16. Nxa1 Qxe2 17. Nb3 Qc4 18. Rd1 Qxf4+ 19. Kb1 Rf8 20. a6 bxa6 21. Qg2 Qb4 22. Qa8+ Kc7 23. Qc6+ Kb8 24. Qa8+ Kc7 25. Qc6+ Kb8

1. b3 e5 2. g3 a5 3. f4 exf4 4. gxf4 Ne7 5. Bxg7 Bxg7 6. Qxg7 Ra6 7. Nd3 d5 8. O-O-O Bf5 9. Qb2 Re6 10. Rf2 Nfg6 11. Nc5 Rc6 12. Nd3 Re6 13. Nc3 d4 14. Na4 b6 15. Qa3 Nd5 16. Nab2 f6 17. Re1 Re7 18. Kd1 Be4 19. Bxe4 Rxe4 20. Qa4 c6 21. Qa3 Ndxf4 22. Nc4 Nd5 23. Kc1 Rd7 24. Kb1 Qe7 25. Qxe7 Rexe7 26. e4 dxe3 27. Nxe3 Nxe3 28. Rxe3 Rxe3 29. dxe3 Rd6 30. Rf5 Re6 31. Kc1 Rxe3 32. Rxf6 Kc7 33. Nf2 Re5 34. Rf7+ Re7 35. Rf6 Re5 36. Rf7+ Re7 37. Rf5 Re5

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 83 / 919 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): rkbrqnnb/pppppppp/8/8/8/8/PPPPPPPP/BNNRKRQB w DFad - 0 1

Mirror twin: White 867 vs Black 34 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 360.