White 255 vs Black 947

The two setups

White: setup #255 N R K Q N R B B

King on the c-file, rooks on b, f, queen on the d-file; one bishop starts in a corner; the knights start away from the centre. The king already stands on a castled square, so one of the castlings moves only the rook. In ordinary symmetric play setup 255 gives White +0.16 (Morozov Balance Index, 400M nodes).

Black: setup #947 B R K R N N Q B

King on the c-file, rooks on b, d, queen on the g-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 947 gives White +0.32 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B, 3.2B nodes) the evaluation is exactly 0.00 each time, reaching search depth 63.

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 0 and +24 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 255 gives White +0.16 and setup 947 gives White +0.32: with both sides on the same rank the first move is worth something. In this pair Black's own setup absorbs that edge completely.

The engine's first choice for White is g3; the alternatives are slightly weaker but keep the game level.

Along the engine's main line (8 moves) the evaluation stayed within ±0 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 16 000 000 000 nodes.

Swap the two setups, giving White the black back rank and Black the white one, and the evaluation jumps to +102. The same two armies dealt the other way round are no longer balanced at all: that is how precisely this pair pays for the first move.

Independent engines, run on the same position:

• Berserk 14: 0
• Lc0 0.32.1: +14

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 +28, Black +72, difference -44. A balanced pair needs White's setup to be weaker by about the price of the first move.

Extended self-play: 160 games, 0 White wins, 160 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

8 moves, 5 000 000 nodes per half-move. Largest |evaluation| 0 cp, mean 0.0 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 30.9 moves.

1. g4 g6 2. f4 f5 3. gxf5 gxf5 4. Bxa7 Qxa2 5. Bxb8 Bxb2+ 6. Rxb2 Qxa1+ 7. Rb1 Qa3+ 8. Rb2 Qa1+ 9. Rb1 Qa3+ 10. Rb2

1. g4 g6 2. f4 b6 3. Bxa8 Rxa8 4. e4 f5 5. gxf5 Qxa2 6. e5 Qd5 7. fxg6 Nxg6 8. Qh5 Qf7 9. Qf3 c6 10. Ng2 Kb7 11. Nb3 Nc7 12. d4 e6 13. O-O-O a5 14. Nd2 d5 15. exd6 Nb5 16. Ne3 Nxd6 17. Nec4 Nxc4 18. Nxc4 Ne7 19. Qa3 Nc8 20. Kb1 a4 21. Bf2 Rd5 22. Rg1 Bf6 23. Qf3 Bh8 24. Rd3 b5 25. Ne5 Qe7 26. Qh3 Nb6 27. Rdg3 a3 28. Rxa3 Rxa3 29. Qxa3 Qxa3 30. bxa3 Bxe5 31. dxe5 Na4 32. Rg7+ Kc8 33. Rg8+ Kd7 34. Rg7+ Kc8 35. Kc1 Nc3 36. f5 Rd1+ 37. Kb2 Na4+ 38. Ka2 Rd2 39. fxe6 Rxf2 40. Rg8+ Kc7

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 255 / 947 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): brkrnnqb/pppppppp/8/8/8/8/PPPPPPPP/NRKQNRBB w BFbd - 0 1

Mirror twin: White 608 vs Black 3 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 51.