White 19 vs Black 400

The two setups

White: setup #19 B N Q N R K R B

King on the f-file, rooks on e, g, queen on the c-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 19 gives White +0.30 (Morozov Balance Index, 400M nodes).

Black: setup #400 B B R Q N N K R

King on the g-file, rooks on c, h, queen on the d-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 400 gives White +0.31 (Morozov Balance Index, 400M nodes).

Why the pair is balanced

At the deepest rungs (400M, 800M, 1.6B nodes) the evaluation never left ±1 centipawns of equality, 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 -24 and -1 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 19 gives White +0.30 and setup 400 gives White +0.31: 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 (30 moves) the largest swing was 44 cp (around move 8), ending at 0 cp — the position stays playable for both sides.

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: 0

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 +80, Black +124, difference -44. 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

30 moves, 5 000 000 nodes per half-move. Largest |evaluation| 44 cp, mean 9.8 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 50.6 moves.

1. g3 d5 2. d4 b6 3. c4 h5 4. h4 Rh6 5. b4 Nf6 6. Ne3 Qd7 7. Bg2 c6 8. c5 a5 9. cxb6 axb4 10. Nd2 Ng4 11. Nxg4 hxg4 12. O-O e5 13. Nb3 e4 14. Nc5 Qd8 15. b7 Bxb7 16. Nxb7 Qe7 17. Nc5 Rxh4 18. Nxe4 dxe4 19. Qc5 Qxc5 20. dxc5 Rh5 21. Rb1 e3 22. Bd4 exf2+ 23. Bxf2 Re5 24. Rxb4 Rxe2 25. a4 Ra2 26. Re1 Nd7 27. Rxg4 Ne5 28. Rge4 f6 29. R1e2 Ra1+ 30. Re1 Ra3 31. R1e3 Ra1+ 32. Re1 Ra2 33. R1e2 Ra1+

1. g3 e6 2. d4 d5 3. c4 b6 4. b4 h5 5. h4 Nf6 6. Nd2 c5 7. dxc5 Ng4 8. cxb6 Qxb6 9. Qa3 Nh2+ 10. Kg2 Ng4 11. c5 Qc7 12. Qb2 d4+ 13. e4 Rd8 14. Nf3 Ng6 15. Qc2 d3 16. Qc4 O-O 17. b5 a6 18. a4 Qa7 19. Ne3 axb5 20. axb5 Bxg3 21. b6 Qb8 22. fxg3 d2 23. Nxg4 dxe1=N+ 24. Nxe1 hxg4 25. Nd3 Bb7 26. Kh2 Rd7 27. Rd1 Qd8 28. Bg2 Nxh4 29. gxh4 Qxh4+ 30. Kg1 Rfd8 31. Be5 g3 32. Kf1 Qh5 33. Ke1 Rc8 34. Bd4 Qh2 35. Rd2 Rcd8 36. Be3 Kh7 37. c6 Bxc6 38. Bf3 Qh4 39. Qxc6 Rxd3 40. Rxd3 Rxd3 41. Ke2 Ra3 42. e5 Ra2+ 43. Bd2 Qh2+ 44. Bg2 Qg1 45. Qf3 Qxb6 46. Qxg3 Qb4 47. Qd3+ g6 48. Qe3 Qg4+ 49. Qf3 Qf5 50. Qxf5 gxf5 51. Bc6 Kg6 52. Bf3 f6 53. exf6 Kxf6 54. Kd3 e5 55. Bc3 Ra7 56. Bc6 Ke6 57. Bb5 Rb7 58. Bc4+ Kf6 59. Ba6 Rd7+ 60. Ke3 Ra7 61. Bb5 Rc7 62. Be1 Rb7 63. Bh4+ Kf7 64. Ba6 Rb3+ 65. Kd2 Rb4 66. Be1 Kg6 67. Kc2 Rb6 68. Bc4 Kg5 69. Kd3 Rd6+ 70. Ke2 Rh6 71. Bd2+ f4 72. Bd3 Kg4 73. Be1 Rh8 74. Be4 Rh3 75. Bc6 Re3+ 76. Kf2 Rd3 77. Ba5 Kf5 78. Ke2 e4 79. Bb7 Re3+ 80. Kf1 Rb3 81. Bc6 Ke5 82. Bd8 Kd4 83. Kg2 Ke3 84. Bh4 Rb2+ 85. Kh3 Rb6 86. Be8 Rb8 87. Bf7 Rb7 88. Bc4 Rg7 89. Bd5 f3 90. Bg3 Rd7 91. Bc6 Rh7+ 92. Kg4 Rg7+ 93. Kh3 Rh7+ 94. Kg4 Rg7+ 95. Kh3

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 19 / 400 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): bbrqnnkr/pppppppp/8/8/8/8/PPPPPPPP/BNQNRKRB w EGch - 0 1

Mirror twin: White 931 vs Black 751 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 110.