White 173 vs Black 319

The two setups

White: setup #173 N R N B K Q B R

King on the e-file, rooks on b, h, queen on the f-file; no bishop starts in a corner; the knights start away from the centre. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 173 gives White +0.36 (Morozov Balance Index, 400M nodes).

Black: setup #319 N Q R K R N B B

King on the d-file, rooks on c, e, queen on the b-file; one bishop starts in a corner; the knights start away from the centre. Castling follows the Chess960 rule: king and rook end on the classical squares. In ordinary symmetric play setup 319 gives White +0.20 (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 60.

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 -20 and +10 cp before settling — a reminder that quick engine checks overstate imbalances, and why the ladder goes deep.

For comparison, in symmetric play setup 173 gives White +0.36 and setup 319 gives White +0.20: 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 b4; the alternatives are slightly weaker but keep the game level.

Along the engine's main line (10 moves) the evaluation stayed within ±19 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 1, drawn 9, Black won 0 (White scored 55.0%).

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: -6

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 +2, Black +34, difference -32. A balanced pair needs White's setup to be weaker by about the price of the first move.

Extended self-play: 10 games, 1 White wins, 9 draws, 0 Black wins, White scored 55.0%.

Best first moves

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

Main-line play-out

10 moves, 5 000 000 nodes per half-move. Largest |evaluation| 19 cp, mean 2.9 cp, final 0 cp.

Engine self-play

10 games at 500 000 nodes per move: White won 1, drawn 9, Black won 0 — White scored 55.0%. Average length 60.6 moves.

1. b4 Nb6 2. f4 Nc4 3. Bd4 f5 4. Nd3 d6 5. Nb3 Nd7 6. e3 a5 7. Nxa5 c5 8. Bc3 cxb4 9. Bxb4 g6 10. Nxc4 Bxc4 11. a3 Nf6 12. Ba5+ Kd7 13. Be2 Qa8 14. Bb4 b5 15. c3 Ba2 16. Ra1 Bd5 17. Bf3 Qc6 18. Qe2 Bxf3 19. Qxf3 Qc4 20. Qe2 Ke6 21. Nf2 Nd5 22. g3 Kd7 23. e4 Qxe2+ 24. Kxe2 Nb6 25. Kd1 h5 26. Re1 e5 27. fxe5 Rxe5 28. Rb1 h4 29. g4 Kc6 30. c4 Nxc4 31. d3 Nb6 32. Rc1+ Kd7 33. Rxc8 Nxc8 34. Rf1 fxe4 35. Nxe4 Re8 36. Rf7+ Kc6 37. Rh7 Be5 38. Rxh4 Ne7 39. Rh6 Rf8 40. Ke2 Nd5 41. h4 Nf4+ 42. Kd2 Kd5 43. Nc3+ Kc6 44. Ne4 Kd5 45. Nc3+ Kc6

1. b4 Nb6 2. c3 f5 3. Bb3 Nc4 4. Nc2 b5 5. f3 g5 6. h4 g4 7. Qf2 c6 8. fxg4 fxg4 9. Nd3 d6 10. Qf4 Nd7 11. Qxg4 Nf6 12. Qf3 Bd5 13. Qh3 e5 14. h5 Qb7 15. Ne3 Ne4 16. Bxc4 bxc4 17. Nb2 Qe7 18. Nbxc4 Be6 19. g4 d5 20. Na5 Qg5 21. Qf3 Kd7 22. Nb3 Rf8 23. Qg2 Rb8 24. Rh3 Rg8 25. Bf2 a5 26. Nxa5 Ra8 27. Nb3 Rxa2 28. c4 Ke8 29. Bh4 Qf4 30. Rf3 Qh6 31. cxd5 cxd5 32. b5 Kd7 33. Qf1 Kc8 34. Nf5 Bxf5 35. Rxf5 Kb8 36. b6 Rc8 37. Qf3 Nxd2 38. Nxd2 Qxd2+ 39. Kf1 Qc2 40. Re1 Qc3 41. Rf7 Qxf3+ 42. exf3 d4 43. Bg3 Rc5 44. Rb1 Rc8 45. Rxh7 Ra5 46. b7 Rg8 47. g5 d3 48. h6 Re8 49. Rd1 d2 50. Rxd2 Rc5 51. Ra2 Rc1+ 52. Kg2 Rc2+ 53. Rxc2 Rd8 54. Rf7

Play it in the CH960 app

Open this page on a phone with the CH960 app installed, or find pair 173 / 319 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): nqrkrnbb/pppppppp/8/8/8/8/PPPPPPPP/NRNBKQBR w BHce - 0 1

Mirror twin: White 792 vs Black 352 — a different position (castling squares are fixed), not evaluated by the search.

Current place in the live balance rating: 37.