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Hi,

Here:

[d]r7/pR4pk/1b2p3/1Np3p1/2p5/8/PP4PP/6K1 w - - 0 29

White played 29.Nc3 and you can see what happened in the game. What would occur in case of 29.Nd6 .

[pgn][Event "Madrid"] [Site "Madrid ESP"] [Date "1933.06.??"] [EventDate "?"] [Round "?"] [Result "0-1"] [White "Martin Ortueta Esteban"] [Black "Jose Sanz Aguado"] [ECO "C00"] [WhiteElo "?"] [BlackElo "?"] [PlyCount "70"] 1. e4 e6 2. d3 d5 3. Nc3 Nf6 4. e5 Nfd7 5. f4 Bb4 6. Bd2 O-O 7. Nf3 f6 8. d4 c5 9. Nb5 fxe5 10. dxe5 Rxf4 11. c3 Re4+ 12. Be2 Ba5 13. O-O Nxe5 14. Nxe5 Rxe5 15. Bf4 Rf5 16. Bd3 Rf6 17. Qc2 h6 18. Be5 Nd7 19. Bxf6 Nxf6 20. Rxf6 Qxf6 21. Rf1 Qe7 22. Bh7+ Kh8 23. Qg6 Bd7 24. Rf7 Qg5 25. Qxg5 hxg5 26. Rxd7 Kxh7 27. Rxb7 Bb6 28. c4 dxc4 29. Nc3 Rd8 30. h3 Rd2 31. Na4 Rxb2 32. Nxb2 c3 33. Rxb6 c4 34. Rb4 a5 35. Nxc4 c2 0-1[/pgn]

29.Nd6 is draw

Paloma wrote: ↑Sat Aug 03, 2019 2:01 pm29.Nd6 is draw

Indeed. After a forward/backward analysis, Cfish-dev says 0.00, in a variety of ways:

0.00 29... Bd8 30. h3 Bf6 31. Nxc4 Bd4+ 32. Kh2 g4 33. Re7 Kg6 34. Rxe6+ Kf5 35. Re7 gxh3 36. gxh3 a5 37. Kg3 a4 38. Nb6 Ra6 39. Nc4 Rg6+ 40. Kf3 Rh6 41. Kg3 Rg6+ (depth 45, 0:01:39)

0.00 29... c3 30. bxc3 c4+ 31. Kf1 Rf8+ 32. Rf7 Rxf7+ 33. Nxf7 Kg6 34. Ne5+ Kf5 35. Nxc4 Bc7 36. h3 Be5 37. Ke2 Bxc3 38. Kf3 Kf6 39. Nd6 Bb4 40. Nc4 (depth 45, 0:01:39)

0.00 29... Rf8 30. Nxc4 Bd8 31. h3 Kg6 32. Rxa7 Bf6 33. g4 Bd4+ 34. Kg2 Rf4 35. b3 e5 36. Ra6+ Kf7 37. Ra7+ Ke6 38. Rxg7 e4 39. Rg6+ Bf6 40. Rg8 Kf7 41. Ra8 Bd4 42. Ra7+ Ke8 43. Ra8+ Kd7 44. Kg3 Rf3+ 45. Kg2 (depth 45, 0:01:39)

0.00 29... Kg6 30. Re7 Kf6 31. Rf7+ Kg6 (depth 45, 0:01:39)

0.00 29... Rd8 30. Nxc4 Rd1+ 31. Kf2 Rc1 32. b3 Rc2+ 33. Kf3 Rxa2 34. Nxb6 axb6 35. Rxb6 Kg6 36. Rxe6+ Kf5 37. Re3 g4+ 38. Kg3 Rc2 39. h3 gxh3 40. gxh3 Rc1 41. Kg2 Kf4 42. Rf3+ Ke4 43. Rg3 Rc2+ 44. Kg1 Rb2 45. Kf1 Kf4 46. Rxg7 Rxb3 (depth 45, 0:01:39)

zullil wrote: ↑Sat Aug 03, 2019 4:20 pm

Paloma wrote: ↑Sat Aug 03, 2019 2:01 pm29.Nd6 is draw

Indeed. After a forward/backward analysis, Cfish-dev says 0.00, in a variety of ways:

[...]

I believe forward/backward analysis is better than infinite analysis.

dupe of http://www.chessgames.com/perl/chessgame?gid=1277959 ?

whereagles wrote: ↑Sun Aug 04, 2019 11:22 pm dupe of http://www.chessgames.com/perl/chessgame?gid=1277959 ?

IMHO this can not be an accident. We should search databases for earliest occurrence of something like:

[d]8/p7/1b6/2p5/N1p5/8/PP6/8 b - - 0 1

the issue was debated here: https://timkr.home.xs4all.nl/chess/rxb2.htm

outcome was inconclusive, though

Look wrote: ↑Sat Aug 03, 2019 5:25 pm

zullil wrote: ↑Sat Aug 03, 2019 4:20 pm

Paloma wrote: ↑Sat Aug 03, 2019 2:01 pm29.Nd6 is draw

Indeed. After a forward/backward analysis, Cfish-dev says 0.00, in a variety of ways:

[...]

I believe forward/backward analysis is better than infinite analysis.

but forward backward analysis assumes the solution. Otherwise, what are you going backwards from?

Dann Corbit wrote: ↑Tue Aug 06, 2019 7:56 am

Look wrote: ↑Sat Aug 03, 2019 5:25 pm

zullil wrote: ↑Sat Aug 03, 2019 4:20 pm

Paloma wrote: ↑Sat Aug 03, 2019 2:01 pm29.Nd6 is draw

Indeed. After a forward/backward analysis, Cfish-dev says 0.00, in a variety of ways:

[...]

I believe forward/backward analysis is better than infinite analysis.

but forward backward analysis assumes the solution. Otherwise, what are you going backwards from?

I am not sure whether I understand your question fully, so you may explain more. But from what I infer, first we have forward analysis until we find an important but neglected move. Then backward analysis and now engine knows about that move to begin with. The cycle goes on till you have a complete image of the initial position.

Look wrote: ↑Tue Aug 06, 2019 1:24 pm

Dann Corbit wrote: ↑Tue Aug 06, 2019 7:56 am

Look wrote: ↑Sat Aug 03, 2019 5:25 pm

zullil wrote: ↑Sat Aug 03, 2019 4:20 pm

Paloma wrote: ↑Sat Aug 03, 2019 2:01 pm29.Nd6 is draw

Indeed. After a forward/backward analysis, Cfish-dev says 0.00, in a variety of ways:

[...]

I believe forward/backward analysis is better than infinite analysis.

but forward backward analysis assumes the solution. Otherwise, what are you going backwards from?

I am not sure whether I understand your question fully, so you may explain more. But from what I infer, first we have forward analysis until we find an important but neglected move. Then backward analysis and now engine knows about that move to begin with. The cycle goes on till you have a complete image of the initial position.

what you are describing is more like the analysis performed by Aquarium, where lines are explored iteratively.
Perhaps it is my ignorance of the nomenclature, but what I call forwards and backwards analysis involves taking a pre-existing plan/pv/game/ and analysing backwards and forwards over the projected nodes, choosing new nodes when the engine finds improvements,