White 49 vs Black 483

The two setups

White: setup #49 B N N B R Q K R

King on the g-file, rooks on e, h, queen on the f-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 49 gives White +0.26 (Morozov Balance Index, 400M nodes).

Black: setup #483 B Q R N K N R B

King on the e-file, rooks on c, g, queen on the b-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 483 gives White +0.10 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation never left ±2 centipawns of equality, reaching search depth 56.

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 ±13 cp.

For comparison, in symmetric play setup 49 gives White +0.26 and setup 483 gives White +0.10: 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 b4, and 2 first moves are within 10 cp of it.

Along the engine's main line (27 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: -6
• Lc0 0.32.1: -3

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 +96, Black +150, difference -54. 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

27 moves, 5 000 000 nodes per half-move. Largest |evaluation| 16 cp, mean 2.2 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 45.3 moves.

1. b3 b5 2. e4 Nfe6 3. Na3 a6 4. c4 b4 5. Nc2 c5 6. Nd3 g6 7. Bxh8 Rxh8 8. f4 Nc6 9. Ne3 O-O-O 10. Qf2 d6 11. Bg4 Qb7 12. O-O Kb8 13. Bxe6 fxe6 14. Nc2 Rhf8 15. Qg3 Rf7 16. Rf2 a5 17. h3 Qc7 18. Re3 Rg8 19. Nce1 Qd8 20. Nf3 h6 21. e5 Bb7 22. Qh4 Qf8 23. exd6 exd6 24. Rxe6 Bc8 25. Re3 Bd7 26. Kh2 Kc7 27. Rfe2 Kb6 28. Qg3 Rf6 29. Re4 Bf5 30. R4e3 Bd7 31. Re1 Rg7 32. Re4 Rgf7 33. R1e2 Kb7 34. Nde1 Rxf4 35. Rxf4 Rxf4 36. Qxg6 a4 37. Qg3 axb3 38. axb3 Na5 39. Nd3 Rf7 40. Nh4 Nxb3 41. Ng6 Qb8 42. Nxb4 Nd4 43. Re4 Bf5 44. Rxd4 cxd4 45. Nf4 d5 46. Nbxd5 Be4 47. Ne6 Qxg3+ 48. Kxg3 Bxd5 49. cxd5 Rf5

1. b3 b5 2. e4 Nfe6 3. Na3 a6 4. c4 b4 5. Nc2 c5 6. Nd3 g6 7. Bxh8 Rxh8 8. f4 Nc6 9. Ne3 O-O-O 10. Qf2 d6 11. Bg4 Qb7 12. O-O Kb8 13. Bxe6 fxe6 14. Nc2 Rhf8 15. Qg3 Rf7 16. Rf2 a5 17. h3 Qc7 18. Re3 Rg8 19. Nce1 Qd8 20. Nf3 h6 21. e5 Bb7 22. Qh4 Qf8 23. exd6 exd6 24. Rxe6 Bc8 25. Re3 Bd7 26. Kh2 Kc7 27. Rfe2 Kb6 28. Qg3 Rf6 29. Re4 Bf5 30. R4e3 Bd7 31. Re1 Rg7 32. Re4 Rgf7 33. R1e2 Kb7 34. Nde1 Rxf4 35. Rxf4 Rxf4 36. Qxg6 a4 37. Qg3 axb3 38. axb3 Na5 39. Nd3 Rf7 40. Nh4 Nxb3 41. Ng6 Qb8 42. Nxb4 Nd4 43. Re4 Bf5 44. Rxd4 cxd4 45. Nf4 d5 46. Nbxd5 Be4 47. Ne6 Qxg3+ 48. Kxg3 Bxd5 49. cxd5 Rf5

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 49 / 483 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): bqrnknrb/pppppppp/8/8/8/8/PPPPPPPP/BNNBRQKR w EHcg - 0 1

Mirror twin: White 907 vs Black 563 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 223.