An absolutely brilliant study!

[Andre]

A good exercise would be to find out which engine can show a winning score after move 4 in the mainline.

For those wondering what the main line is:

[pgn][Event "Shakhmatnaya Kompozitsia"]
[Date "2015.09.18"]
[Result "1-0"]
[SetUp "1"]
[FEN "8/2p2p1p/3k1p2/pn6/PNp4p/r3Rp1P/2P2P2/BK6 w - - 0 1"]
[PlyCount "319"]
[EventDate "2015.09.18"]

1. Nd5 $1 (1. c3 $2 Rb3+ 2. Kc1 Na3) (1. Re4 $2 Rxa4 2. Na6 Na3+ 3. Kc1 Nxc2 4. Bxf6 Nb4 5. Nxb4 axb4 6. Rxc4 c5) 1... Kxd5 (1... Rxa1+ ! 2. Kxa1 Nd4 3. Kb2 Kxd5 4. Re7 Ne6 5. Rxf7 Ng5 6. Rxf6 Ke5 7. Rh6 Nxh3 8. Rh5+ Ke6 9. Rxh4 Nxf2 10. Rf4 Nd1+ 11. Kc1 Nc3 12. Rxf3 Nxa4 13. Ra3 Nb6 14. Rxa5 Nd5) 2. Rxa3 Nxa3+ 3. Kb2 c3+ $1 4. Kxa3 Kc4 5. Ka2 Kb4 6. Kb1 Kc4 7. Kc1 Kb4 8. Kd1 Kc4 9. Ke1 Kb4 10. Kf1 Kc4 11. Kg1 Kb4 12. Kh1 (12. Kh2 {<or>}) 12... Kc4 13. Kh2 Kb4 14. Kg1 Kc4 15. Kf1 Kb4 16. Ke1 Kc4 17. Kd1 Kb4 18. Kc1 Kc4 19. Kb1 Kb4 20. Ka2 Kc4 21. Ka3 h6 22. Ka2 Kb4 23. Kb1 Kc4 24. Kc1 Kb4 25. Kd1 Kc4 26. Ke1 Kb4 27. Kf1 Kc4 28. Kg1 Kb4 29. Kh2 Kc4 30. Kh1 Kb4 31. Kg1 Kc4 32. Kf1 Kb4 33. Ke1 Kc4 34. Kd1 Kb4 35. Kc1 Kc4 36. Kb1 Kb4 37. Ka2 Kc4 38. Ka3 h5 39. Ka2 Kb4 40. Kb1 Kc4 41. Kc1 Kb4 42. Kd1 Kc4 43. Ke1 Kb4 44. Kf1 Kc4 45. Kg1 Kb4 46. Kh2 Kc4 47. Kh1 Kb4 48. Kg1 Kc4 49. Kf1 Kb4 50. Ke1 Kc4 51. Kd1 Kb4 52. Kc1 Kc4 53. Kb1 Kb4 54. Ka2 Kc4 55. Ka3 f5 56. Ka2 Kb4 57. Kb1 Kc4 58. Kc1 Kb4 59. Kd1 Kc4 60. Ke1 Kb4 61. Kf1 Kc4 62. Kg1 Kb4 63. Kh1 Kc4 64. Kh2 Kb4 65. Kg1 Kc4 66. Kf1 Kb4 67. Ke1 Kc4 68. Kd1 Kb4 69. Kc1 Kc4 70. Kb1 Kb4 71. Ka2 Kc4 72. Ka3 f4 73. Ka2 Kb4 74. Kb1 Kc4 75. Kc1 Kb4 76. Kd1 Kc4 77. Ke1 Kb4 78. Kf1 Kc4 79. Kg1 Kb4 80. Kh2 Kc4 81. Kh1 Kb4 82. Kg1 Kc4 83. Kf1 Kb4 84. Ke1 Kc4 85. Kd1 Kb4 86. Kc1 Kc4 87. Kb1 Kb4 88. Ka2 Kc4 89. Ka3 f6 90. Ka2 Kb4 91. Kb1 Kc4 92. Kc1 Kb4 93. Kd1 Kc4 94. Ke1 Kb4 95. Kf1 Kc4 96. Kg1 Kb4 97. Kh2 Kc4 98. Kh1 Kb4 99. Kg1 Kc4 100. Kf1 Kb4 101. Ke1 Kc4 102. Kd1 Kb4 103. Kc1 Kc4 104. Kb1 Kb4 105. Ka2 Kc4 106. Ka3 f5 107. Ka2 Kb4 108. Kb1 Kc4 109. Kc1 Kb4 110. Kd1 Kc4 111. Ke1 Kb4 112. Kf1 Kc4 113. Kg1 Kb4 114. Kh2 Kc4 115. Kh1 Kb4 116. Kg1 Kc4 117. Kf1 Kb4 118. Ke1 Kc4 119. Kd1 Kb4 120. Kc1 Kc4 121. Kb1 Kb4 122. Ka2 Kc4 123. Ka3 c6 124. Ka2 Kb4 125. Kb1 Kc4 126. Kc1 Kb4 127. Kd1 Kc4 128. Ke1 Kb4 129. Kf1 Kc4 130. Kg1 Kb4 131. Kh2 Kc4 132. Kh1 Kb4 133. Kg1 Kc4 134. Kf1 Kb4 135. Ke1 Kc4 136. Kd1 Kb4 137. Kc1 Kc4 138. Kb1 Kb4 139. Ka2 Kc4 140. Ka3 c5 141. Ka2 Kb4 142. Kb1 Kc4 143. Kc1 Kb4 144. Kd1 Kc4 145. Ke1 Kb4 146. Kf1 Kc4 147. Kg1 Kb4 148. Kh2 Kc4 149. Kh1 Kb4 150. Kg1 Kc4 151. Kf1 Kb4 152. Ke1 Kc4 153. Kd1 Kb4 154. Kc1 Kc4 155. Kb1 Kb4 156. Ka2 Kc4 157. Ka3 Kd4 158. Kb3 c4+ 159. Ka3 Kc5 160. Bxc3 1-0

[/pgn]

[Dann Corbit]

[pgn][Event "sp.p Shakhmatnaya Kompozitsia#21"]
[Site "?"]
[Date "2015.09.18"]
[Round "?"]
[White "Zemlyansky=Y"]
[Black "(+0414.48b1d6) U3"]
[Result "1-0"]
[SetUp "1"]
[FEN "8/2p2p1p/3k1p2/pn6/PNp4p/r3Rp1P/2P2P2/BK6 w - - 0 1"]
[PlyCount "319"]
[EventDate "2015.09.18"]

{Shakhmatnaya Kompozitsia=125 . U3: Garcia=M EG=205 7/2016.} 1. Nd5 $1 (1. c3 $2 Rb3+ 2. Kc1 Na3)
(1. Re4 $2 Rxa4 2. Na6 Na3+ 3. Kc1 Nxc2 4. Bxf6 Nb4 5. Nxb4 axb4 6. Rxc4 c5)
1... Kxd5 (1... Rxa1+ $1 {<cook MG>} 2. Kxa1 Nd4 3. Kb2 Kxd5 4. Re7 Ne6 5. Rxf7
Ng5 6. Rxf6 Ke5 7. Rh6 Nxh3 8. Rh5+ Ke6 9. Rxh4 Nxf2 10. Rf4 Nd1+ 11. Kc1 Nc3
12. Rxf3 Nxa4 13. Ra3 Nb6 14. Rxa5 Nd5) 2. Rxa3 Nxa3+ 3. Kb2 c3+ $1 4. Kxa3 Kc4
5. Ka2 Kb4 6. Kb1 Kc4 7. Kc1 Kb4 8. Kd1 Kc4 9. Ke1 Kb4 10. Kf1 Kc4 11. Kg1 Kb4
12. Kh1 (12. Kh2 {<or>}) 12... Kc4 13. Kh2 Kb4 14. Kg1 Kc4 15. Kf1 Kb4 16. Ke1
Kc4 17. Kd1 Kb4 18. Kc1 Kc4 19. Kb1 Kb4 20. Ka2 Kc4 21. Ka3 h6 22. Ka2 Kb4 23.
Kb1 Kc4 24. Kc1 Kb4 25. Kd1 Kc4 26. Ke1 Kb4 27. Kf1 Kc4 28. Kg1 Kb4 29. Kh2 Kc4
30. Kh1 Kb4 31. Kg1 Kc4 32. Kf1 Kb4 33. Ke1 Kc4 34. Kd1 Kb4 35. Kc1 Kc4 36. Kb1
Kb4 37. Ka2 Kc4 38. Ka3 h5 39. Ka2 Kb4 40. Kb1 Kc4 41. Kc1 Kb4 42. Kd1 Kc4 43.
Ke1 Kb4 44. Kf1 Kc4 45. Kg1 Kb4 46. Kh2 Kc4 47. Kh1 Kb4 48. Kg1 Kc4 49. Kf1 Kb4
50. Ke1 Kc4 51. Kd1 Kb4 52. Kc1 Kc4 53. Kb1 Kb4 54. Ka2 Kc4 55. Ka3 f5 56. Ka2
Kb4 57. Kb1 Kc4 58. Kc1 Kb4 59. Kd1 Kc4 60. Ke1 Kb4 61. Kf1 Kc4 62. Kg1 Kb4 63.
Kh1 Kc4 64. Kh2 Kb4 65. Kg1 Kc4 66. Kf1 Kb4 67. Ke1 Kc4 68. Kd1 Kb4 69. Kc1 Kc4
70. Kb1 Kb4 71. Ka2 Kc4 72. Ka3 f4 73. Ka2 Kb4 74. Kb1 Kc4 75. Kc1 Kb4 76. Kd1
Kc4 77. Ke1 Kb4 78. Kf1 Kc4 79. Kg1 Kb4 80. Kh2 Kc4 81. Kh1 Kb4 82. Kg1 Kc4 83.
Kf1 Kb4 84. Ke1 Kc4 85. Kd1 Kb4 86. Kc1 Kc4 87. Kb1 Kb4 88. Ka2 Kc4 89. Ka3 f6
90. Ka2 Kb4 91. Kb1 Kc4 92. Kc1 Kb4 93. Kd1 Kc4 94. Ke1 Kb4 95. Kf1 Kc4 96. Kg1
Kb4 97. Kh2 Kc4 98. Kh1 Kb4 99. Kg1 Kc4 100. Kf1 Kb4 101. Ke1 Kc4 102. Kd1 Kb4
103. Kc1 Kc4 104. Kb1 Kb4 105. Ka2 Kc4 106. Ka3 f5 107. Ka2 Kb4 108. Kb1 Kc4
109. Kc1 Kb4 110. Kd1 Kc4 111. Ke1 Kb4 112. Kf1 Kc4 113. Kg1 Kb4 114. Kh2 Kc4
115. Kh1 Kb4 116. Kg1 Kc4 117. Kf1 Kb4 118. Ke1 Kc4 119. Kd1 Kb4 120. Kc1 Kc4
121. Kb1 Kb4 122. Ka2 Kc4 123. Ka3 c6 124. Ka2 Kb4 125. Kb1 Kc4 126. Kc1 Kb4
127. Kd1 Kc4 128. Ke1 Kb4 129. Kf1 Kc4 130. Kg1 Kb4 131. Kh2 Kc4 132. Kh1 Kb4
133. Kg1 Kc4 134. Kf1 Kb4 135. Ke1 Kc4 136. Kd1 Kb4 137. Kc1 Kc4 138. Kb1 Kb4
139. Ka2 Kc4 140. Ka3 c5 141. Ka2 Kb4 142. Kb1 Kc4 143. Kc1 Kb4 144. Kd1 Kc4
145. Ke1 Kb4 146. Kf1 Kc4 147. Kg1 Kb4 148. Kh2 Kc4 149. Kh1 Kb4 150. Kg1 Kc4
151. Kf1 Kb4 152. Ke1 Kc4 153. Kd1 Kb4 154. Kc1 Kc4 155. Kb1 Kb4 156. Ka2 Kc4
157. Ka3 Kd4 158. Kb3 c4+ 159. Ka3 Kc5 160. Bxc3 1-0
[/pgn]

[Dann Corbit]

My source was hhdbvi

[acase]

[pgn][Event "sp.p Shakhmatnaya Kompozitsia#21"]
[Site "?"]
[Date "2015.09.18"]
[Round "?"]
[White "Zemlyansky=Y"]
[Black "(+0414.48b1d6) U3"]
[Result "1-0"]
[SetUp "1"]
[FEN "8/2p2p1p/3k1p2/pn6/PNp4p/r3Rp1P/2P2P2/BK6 w - - 0 1"]
[PlyCount "319"]
[EventDate "2015.09.18"]

{Shakhmatnaya Kompozitsia=125 . U3: Garcia=M EG=205 7/2016.} 1. Nd5 $1 (1. c3 $2 Rb3+ 2. Kc1 Na3)
(1. Re4 $2 Rxa4 2. Na6 Na3+ 3. Kc1 Nxc2 4. Bxf6 Nb4 5. Nxb4 axb4 6. Rxc4 c5)
1... Kxd5 (1... Rxa1+ $1 {<cook MG>} 2. Kxa1 Nd4 3. Kb2 Kxd5 4. Re7 Ne6 5. Rxf7
Ng5 6. Rxf6 Ke5 7. Rh6 Nxh3 8. Rh5+ Ke6 9. Rxh4 Nxf2 10. Rf4 Nd1+ 11. Kc1 Nc3
12. Rxf3 Nxa4 13. Ra3 Nb6 14. Rxa5 Nd5) 2. Rxa3 Nxa3+ 3. Kb2 c3+ $1 4. Kxa3 Kc4
5. Ka2 Kb4 6. Kb1 Kc4 7. Kc1 Kb4 8. Kd1 Kc4 9. Ke1 Kb4 10. Kf1 Kc4 11. Kg1 Kb4
12. Kh1 (12. Kh2 {<or>}) 12... Kc4 13. Kh2 Kb4 14. Kg1 Kc4 15. Kf1 Kb4 16. Ke1
Kc4 17. Kd1 Kb4 18. Kc1 Kc4 19. Kb1 Kb4 20. Ka2 Kc4 21. Ka3 h6 22. Ka2 Kb4 23.
Kb1 Kc4 24. Kc1 Kb4 25. Kd1 Kc4 26. Ke1 Kb4 27. Kf1 Kc4 28. Kg1 Kb4 29. Kh2 Kc4
30. Kh1 Kb4 31. Kg1 Kc4 32. Kf1 Kb4 33. Ke1 Kc4 34. Kd1 Kb4 35. Kc1 Kc4 36. Kb1
Kb4 37. Ka2 Kc4 38. Ka3 h5 39. Ka2 Kb4 40. Kb1 Kc4 41. Kc1 Kb4 42. Kd1 Kc4 43.
Ke1 Kb4 44. Kf1 Kc4 45. Kg1 Kb4 46. Kh2 Kc4 47. Kh1 Kb4 48. Kg1 Kc4 49. Kf1 Kb4
50. Ke1 Kc4 51. Kd1 Kb4 52. Kc1 Kc4 53. Kb1 Kb4 54. Ka2 Kc4 55. Ka3 f5 56. Ka2
Kb4 57. Kb1 Kc4 58. Kc1 Kb4 59. Kd1 Kc4 60. Ke1 Kb4 61. Kf1 Kc4 62. Kg1 Kb4 63.
Kh1 Kc4 64. Kh2 Kb4 65. Kg1 Kc4 66. Kf1 Kb4 67. Ke1 Kc4 68. Kd1 Kb4 69. Kc1 Kc4
70. Kb1 Kb4 71. Ka2 Kc4 72. Ka3 f4 73. Ka2 Kb4 74. Kb1 Kc4 75. Kc1 Kb4 76. Kd1
Kc4 77. Ke1 Kb4 78. Kf1 Kc4 79. Kg1 Kb4 80. Kh2 Kc4 81. Kh1 Kb4 82. Kg1 Kc4 83.
Kf1 Kb4 84. Ke1 Kc4 85. Kd1 Kb4 86. Kc1 Kc4 87. Kb1 Kb4 88. Ka2 Kc4 89. Ka3 f6
90. Ka2 Kb4 91. Kb1 Kc4 92. Kc1 Kb4 93. Kd1 Kc4 94. Ke1 Kb4 95. Kf1 Kc4 96. Kg1
Kb4 97. Kh2 Kc4 98. Kh1 Kb4 99. Kg1 Kc4 100. Kf1 Kb4 101. Ke1 Kc4 102. Kd1 Kb4
103. Kc1 Kc4 104. Kb1 Kb4 105. Ka2 Kc4 106. Ka3 f5 107. Ka2 Kb4 108. Kb1 Kc4
109. Kc1 Kb4 110. Kd1 Kc4 111. Ke1 Kb4 112. Kf1 Kc4 113. Kg1 Kb4 114. Kh2 Kc4
115. Kh1 Kb4 116. Kg1 Kc4 117. Kf1 Kb4 118. Ke1 Kc4 119. Kd1 Kb4 120. Kc1 Kc4
121. Kb1 Kb4 122. Ka2 Kc4 123. Ka3 c6 124. Ka2 Kb4 125. Kb1 Kc4 126. Kc1 Kb4
127. Kd1 Kc4 128. Ke1 Kb4 129. Kf1 Kc4 130. Kg1 Kb4 131. Kh2 Kc4 132. Kh1 Kb4
133. Kg1 Kc4 134. Kf1 Kb4 135. Ke1 Kc4 136. Kd1 Kb4 137. Kc1 Kc4 138. Kb1 Kb4
139. Ka2 Kc4 140. Ka3 c5 141. Ka2 Kb4 142. Kb1 Kc4 143. Kc1 Kb4 144. Kd1 Kc4
145. Ke1 Kb4 146. Kf1 Kc4 147. Kg1 Kb4 148. Kh2 Kc4 149. Kh1 Kb4 150. Kg1 Kc4
151. Kf1 Kb4 152. Ke1 Kc4 153. Kd1 Kb4 154. Kc1 Kc4 155. Kb1 Kb4 156. Ka2 Kc4
157. Ka3 Kd4 158. Kb3 c4+ 159. Ka3 Kc5 160. Bxc3 1-0
[/pgn]

Well it looks like we "cooked" the so called "cook" 1...Rxd1 in the database PGN, they'll have to fix the database now with 3.Nb4!! in that line (or remove the so called "cook" line altogether).

[acase]

A good exercise would be to find out which engine can show a winning score after move 4 in the mainline.

For those wondering what the main line is:

[pgn][Event "Shakhmatnaya Kompozitsia"]
[Date "2015.09.18"]
[Result "1-0"]
[SetUp "1"]
[FEN "8/2p2p1p/3k1p2/pn6/PNp4p/r3Rp1P/2P2P2/BK6 w - - 0 1"]
[PlyCount "319"]
[EventDate "2015.09.18"]

1. Nd5 $1 (1. c3 $2 Rb3+ 2. Kc1 Na3) (1. Re4 $2 Rxa4 2. Na6 Na3+ 3. Kc1 Nxc2 4. Bxf6 Nb4 5. Nxb4 axb4 6. Rxc4 c5) 1... Kxd5 (1... Rxa1+ ! 2. Kxa1 Nd4 3. Kb2 Kxd5 4. Re7 Ne6 5. Rxf7 Ng5 6. Rxf6 Ke5 7. Rh6 Nxh3 8. Rh5+ Ke6 9. Rxh4 Nxf2 10. Rf4 Nd1+ 11. Kc1 Nc3 12. Rxf3 Nxa4 13. Ra3 Nb6 14. Rxa5 Nd5) 2. Rxa3 Nxa3+ 3. Kb2 c3+ $1 4. Kxa3 Kc4 5. Ka2 Kb4 6. Kb1 Kc4 7. Kc1 Kb4 8. Kd1 Kc4 9. Ke1 Kb4 10. Kf1 Kc4 11. Kg1 Kb4 12. Kh1 (12. Kh2 {<or>}) 12... Kc4 13. Kh2 Kb4 14. Kg1 Kc4 15. Kf1 Kb4 16. Ke1 Kc4 17. Kd1 Kb4 18. Kc1 Kc4 19. Kb1 Kb4 20. Ka2 Kc4 21. Ka3 h6 22. Ka2 Kb4 23. Kb1 Kc4 24. Kc1 Kb4 25. Kd1 Kc4 26. Ke1 Kb4 27. Kf1 Kc4 28. Kg1 Kb4 29. Kh2 Kc4 30. Kh1 Kb4 31. Kg1 Kc4 32. Kf1 Kb4 33. Ke1 Kc4 34. Kd1 Kb4 35. Kc1 Kc4 36. Kb1 Kb4 37. Ka2 Kc4 38. Ka3 h5 39. Ka2 Kb4 40. Kb1 Kc4 41. Kc1 Kb4 42. Kd1 Kc4 43. Ke1 Kb4 44. Kf1 Kc4 45. Kg1 Kb4 46. Kh2 Kc4 47. Kh1 Kb4 48. Kg1 Kc4 49. Kf1 Kb4 50. Ke1 Kc4 51. Kd1 Kb4 52. Kc1 Kc4 53. Kb1 Kb4 54. Ka2 Kc4 55. Ka3 f5 56. Ka2 Kb4 57. Kb1 Kc4 58. Kc1 Kb4 59. Kd1 Kc4 60. Ke1 Kb4 61. Kf1 Kc4 62. Kg1 Kb4 63. Kh1 Kc4 64. Kh2 Kb4 65. Kg1 Kc4 66. Kf1 Kb4 67. Ke1 Kc4 68. Kd1 Kb4 69. Kc1 Kc4 70. Kb1 Kb4 71. Ka2 Kc4 72. Ka3 f4 73. Ka2 Kb4 74. Kb1 Kc4 75. Kc1 Kb4 76. Kd1 Kc4 77. Ke1 Kb4 78. Kf1 Kc4 79. Kg1 Kb4 80. Kh2 Kc4 81. Kh1 Kb4 82. Kg1 Kc4 83. Kf1 Kb4 84. Ke1 Kc4 85. Kd1 Kb4 86. Kc1 Kc4 87. Kb1 Kb4 88. Ka2 Kc4 89. Ka3 f6 90. Ka2 Kb4 91. Kb1 Kc4 92. Kc1 Kb4 93. Kd1 Kc4 94. Ke1 Kb4 95. Kf1 Kc4 96. Kg1 Kb4 97. Kh2 Kc4 98. Kh1 Kb4 99. Kg1 Kc4 100. Kf1 Kb4 101. Ke1 Kc4 102. Kd1 Kb4 103. Kc1 Kc4 104. Kb1 Kb4 105. Ka2 Kc4 106. Ka3 f5 107. Ka2 Kb4 108. Kb1 Kc4 109. Kc1 Kb4 110. Kd1 Kc4 111. Ke1 Kb4 112. Kf1 Kc4 113. Kg1 Kb4 114. Kh2 Kc4 115. Kh1 Kb4 116. Kg1 Kc4 117. Kf1 Kb4 118. Ke1 Kc4 119. Kd1 Kb4 120. Kc1 Kc4 121. Kb1 Kb4 122. Ka2 Kc4 123. Ka3 c6 124. Ka2 Kb4 125. Kb1 Kc4 126. Kc1 Kb4 127. Kd1 Kc4 128. Ke1 Kb4 129. Kf1 Kc4 130. Kg1 Kb4 131. Kh2 Kc4 132. Kh1 Kb4 133. Kg1 Kc4 134. Kf1 Kb4 135. Ke1 Kc4 136. Kd1 Kb4 137. Kc1 Kc4 138. Kb1 Kb4 139. Ka2 Kc4 140. Ka3 c5 141. Ka2 Kb4 142. Kb1 Kc4 143. Kc1 Kb4 144. Kd1 Kc4 145. Ke1 Kb4 146. Kf1 Kc4 147. Kg1 Kb4 148. Kh2 Kc4 149. Kh1 Kb4 150. Kg1 Kc4 151. Kf1 Kb4 152. Ke1 Kc4 153. Kd1 Kb4 154. Kc1 Kc4 155. Kb1 Kb4 156. Ka2 Kc4 157. Ka3 Kd4 158. Kb3 c4+ 159. Ka3 Kc5 160. Bxc3 1-0

[/pgn]

It wouldn't matter from that point on (after move 4 in the main line) either as the engines don't understand the concept of white "losing the move" to force black to exhaust all of his pawn moves and be forced into a zugzwang (so the white King can occupy the critical b3 square and have black to move) where black's king must abandon the c3 pawn so white can capture it with his Bishop because the win is so far away (mate in 177 with best play I think).

[jhellis3]

That is false. Engines, at least many, do understand losing a tempo, aka zugzwang. The issue is the number of 50 move rule resets required to trigger the real zugzwang combined with the length of the maneuver.

Crystal sees it instantly as soon as there is only 1 reset left, and would probably get it eventually with 2 (I didn't let it cook very long).

Each forcing requires 30 ply & it requires 8 before the genuine zugzwang. That is 240 ply. Even with a tremendously low branching factor of 1.5 and dividing in half for Black shuffling, that is 1.5 ^ 120. Of course, there will be a tremendous amount of transpositions, but progress still won't be seen for 240 ply. Thus there will be considerable wasted searching (all the previous searches up to 239 ply).

At a speed similar to the TCEC machine without hash, it would take ~500,000 years to ensure a result, or ~1,125 years if assuming it gets it once at the last reset.

With TTs... who knows, but probably not worth waiting around to find out...

[Jouni]

Yes difficult after executing 100 first moves(!) SF dev is clueless:

Analysis by Stockfish dev-20230319-02e46970:
...
101.Ke1 Kc4 102.Kd1 Kd4 103.Kc1 Kc4 104.Kd1
= (0.00) Depth: 147/82 00:02:32 1589mN, tb=7275586

Also Crystal:

Analysis by Crystal 5 KWK bmi2:
...
101.Ke1 Kc4 102.Kd1 Kb4
= (0.00) Depth: 101/6 00:02:25 1282mN, tb=6587967

[acase]

That is false. Engines, at least many, do understand losing a tempo, aka zugzwang. The issue is the number of 50 move rule resets required to trigger the real zugzwang combined with the length of the maneuver.

Crystal sees it instantly as soon as there is only 1 reset left, and would probably get it eventually with 2 (I didn't let it cook very long).

Each forcing requires 30 ply & it requires 8 before the genuine zugzwang. That is 240 ply. Even with a tremendously low branching factor of 1.5 and dividing in half for Black shuffling, that is 1.5 ^ 120. Of course, there will be a tremendous amount of transpositions, but progress still won't be seen for 240 ply. Thus there will be considerable wasted searching (all the previous searches up to 239 ply).

At a speed similar to the TCEC machine without hash, it would take ~500,000 years to ensure a result, or ~1,125 years if assuming it gets it once at the last reset.

With TTs... who knows, but probably not worth waiting around to find out...

I see what you mean after following this pgn through with the slowchess blitz 2.9 engine watching this study in infinite mode here:

[pgn][Event "Computer chess game"]
[Site "WORKSTATION-PC"]
[Date "2023.03.23"]
[Round "?"]
[White "Workstation"]
[Black "Workstation"]
[Result "1-0"]
[BlackElo "2400"]
[Time "13:38:48"]
[WhiteElo "2400"]
[TimeControl "300+3"]
[SetUp "1"]
[FEN "1k6/1Pp1pp2/KpP5/p1p5/2P1p3/1Pp1P3/2P2P2/8 w - - 1 1"]
[Termination "normal"]
[PlyCount "171"]
[WhiteType "human"]
[BlackType "human"]

1. Kb5 Ka7 2. Ka4 Kb8 3. Ka3 Ka7 4. Ka2 Kb8 5. Ka1 Ka7 6. Kb1 Kb8 7. Ka2
Ka7 8. Ka3 Kb8 9. Ka4 Ka7 10. Kb5 Kb8 11. Ka6 f6 12. Kb5 Ka7 13. Ka4 Kb8
14. Ka3 Ka7 15. Ka2 Kb8 16. Ka1 Ka7 17. Kb1 Kb8 18. Ka2 Ka7 19. Ka3 Kb8 20.
Ka4 Ka7 21. Kb5 Kb8 22. Ka6 f5 23. Kb5 Ka7 24. Ka4 Kb8 25. Ka3 Ka7 26. Ka2
Kb8 27. Ka1 Ka7 28. Kb1 Kb8 29. Ka2 Ka7 30. Ka3 Kb8 31. Ka4 Ka7 32. Kb5 Kb8
33. Ka6 e6 34. Kb5 Ka7 35. Ka4 Kb8 36. Ka3 Ka7 37. Ka2 Kb8 38. Ka1 Ka7 39.
Kb1 Kb8 40. Ka2 Ka7 41. Ka3 Kb8 42. Ka4 Ka7 43. Kb5 Kb8 44. Ka6 e5 45. Kb5
Ka7 46. Ka4 Kb8 47. Ka3 Ka7 48. Ka2 Kb8 49. Ka1 Ka7 50. Kb1 Kb8 51. Ka2 Ka7
52. Ka3 Kb8 53. Ka4 Ka7 54. Kb5 Kb8 55. Ka6 f4 56. Kb5 Ka7 57. Ka4 Kb8 58.
Ka3 Ka7 59. Ka2 Kb8 60. Ka1 Ka7 61. Kb1 Kb8 62. Ka2 Ka7 63. Ka3 Kb8 64. Ka4
Ka7 65. Kb5 Kb8 66. Ka6 f3 67. Kb5 Ka7 68. Ka4 Kb8 69. Ka3 Ka7 70. Ka2 Kb8
71. Ka1 Ka7 72. Kb1 Kb8 73. Ka2 Ka7 74. Ka3 Kb8 75. Ka4 Ka7 76. Kb5 Kb8 77.
Ka6 b5 78. Kxb5 a4 79. bxa4 Ka7 80. Kxc5 Kb8 81. Kd5 Ka7 82. Ke6 Kb8 83.
Kd7 Ka7 84. Kxc7 Ka6 85. b8=Q Ka5 86. Qb5# 1-0[/pgn]


It eventually announced a mate in 65 around move 24, but before move 24 it's eval was bouncing up to +15.11 and then going back down to 0.00 and went incrementally higher and back down with each move then it started fluctuating between +93 and a mate score before settling on mate in 65. Thanks for taking the time to clarify what's going on with the engines in these types of positions.

[jhellis3]

Sadly, I think this may be somewhat cooked. Nd5 is indeed a beautiful move and winning, but letting Crystal do some deep analysis further in, it seems like the engine's top choice Re4 is likely also winning. Getting scores of ~ +4.5 anyway.

[peter]

Sadly, I think this may be somewhat cooked. Nd5 is indeed a beautiful move and winning, but letting Crystal do some deep analysis further in, it seems like the engine's top choice Re4 is likely also winning. Getting scores of ~ +4.5 anyway.

You're right.
Even if the line given in HHdbVI
8/2p2p1p/3k1p2/pn6/PNp4p/r3Rp1P/2P2P2/BK6 w - - 0 1
1.Re4 Rxa4 2.Na6 Na3+ 3.Kc1 Nxc2 4.Bxf6 Nb4 5.Nxb4 axb4 6.Rxc4 c5
is suboptimal at least as for 5.Nxb4? (5.Rd4+! get's the winning eval of >4 of your Crystal's, you wrote about) but also for 4...Nb4?, 4...Na1 5.Be5+ was 2x1-0 with SF dev- Crystal- Crystal- SF dev at 45'+15", 15 threads of 16x3.5GHz and 16G hash each, 6men Syzygys:

[pgn][Event "AMD, Schnellschach 45.0min+15.0sek"]
[Site "Dort"]
[Date "2023.03.23"]
[Round "1"]
[White "Stockfish"]
[Black "Crystal 5 KWK"]
[Result "1-0"]
[Annotator "1.23;1.02"]
[SetUp "1"]
[FEN "8/2p2p1p/3k1p2/pn6/PNp4p/r3Rp1P/2P2P2/BK6 w - - 0 1"]
[PlyCount "199"]
[TimeControl "2700+15"]

{AMD Ryzen 9 5950X 16-Core Processor 3400 MHz W=50.9 plies; 17.780kN/s; 1.197.553.199 TBAs B=37.7 plies; 16.798kN/s; 1.049.727.312 TBAs 0.86;1.04: 'AMD Ryzen 9 5950X 16-Core Processor 3400 MHz W=38.5 plies; 18.854kN/s; 998.624.273 TBAs B=64.0 plies; 22.671kN/s; 1.457.527.477 TBAs '} 1. Re4 Rxa4 2. Na6 Na3+ 3. Kc1 Nxc2 4. Bxf6 Na1 5. Be5+ {Beide letzter Buchzug} Kd5 {1.02/44 172} (5... Kc6 {1.04/54 416} 6. Rf4 {0.86/44 174} Nb3+ {1.03/56 0} 7. Kb2 {0.80/46 171} Kb6 {1.03/58 0} 8. Rf6+ {0.95/47 112} c6 {1.04/61 0} 9. Nc7 {0.91/48 145} Ra1 {1.14/59 44} 10. Nd5+ {0.73/49 194} Kc5 {1.35/53 8} 11. Nc3 {0.72/47 56} Rf1 {1.58/57 130} 12. Bd6+ {0.67/47 42} Kb6 {1.51/59 17} 13. Rxf3 {0.52/45 47} Nc5 {1.64/59 132} 14. Bxc5+ {0.75/48 0} Kxc5 {1.64/60 178} 15. Rf5+ {0.66/50 114} Kd4 {1.77/62 89} 16. Kc2 {0.40/46 55} Rh1 {1.87/78 75} 17. Rf4+ {0.46/47 33} Kc5 {1.98/68 107} 18. Rxh4 {0.50/47 10} Rh2 {1.98/75 43} 19. Nd1 {0.53/49 287} a4 {2.08/68 0} 20. Rh5+ {0.29/48 91} Kb4 {2.24/78 84} 21. Rxh7 {0.53/49 17} a3 {2.24/73 38} 22. Rh8 {0.84/45 32} f5 {2.49/65 200} 23. h4 {0.98/49 27} f4 {2.49/64 30 (Th3)} 24. h5 {0.99/48 255} Rh3 {2.54/66 9} 25. h6 {0.96/50 241} a2 {2.67/69 0} 26. Rb8+ {1.03/42 40} Kc5 {2.67/65 15} 27. Ra8 {0.86/41 29} Rxh6 {2.67/65 37} 28. Rxa2 {1.02/40 8} Rh3 {2.67/62 87} 29. Ra5+ {1.10/44 173} Kd4 {3.08/53 28} 30. Rf5 {1.04/39 4} Ke4 {3.08/59 58} 31. Rc5 {1.00/41 37} Kf3 {3.08/46 30 (Th6)} 32. Rxc6 {2.08/36 70} Rh8 {14.09/45 538 (Th7)} 33. Rxc4 {2.46/36 184} Ra8 {198.30/51 0} 34. Kc1 {2.61/35 163 (Kd2)} Ra1+ {199.02/49 97} 35. Kd2 {2.68/34 7 (Kc2)} Ra7 {198.92/52 30} 36. Rc3+ {2.75/32 19 (Tc5)} Kg2 {199.18/65 28} 37. Kc1 {3.00/33 81 (Kc2)} Ra1+ {199.18/65 39} 38. Kc2 {2.85/31 34} Ra8 {199.24/74 9 (Ta6)} 39. Kb2 {3.50/29 41} Rb8+ {199.26/74 0 (Td8)} 40. Kc1 {3.88/31 74} Ra8 {199.28/70 154 (Te8)} 41. Rc2 {4.87/28 29} Ra1+ {199.30/79 16} 42. Kd2 {5.07/28 22} Kf1 {199.32/80 62 (Ta8)} 43. Rc4 {7.47/28 44} Ra2+ {199.34/81 0} 44. Kc1 {12.58/27 116 (Kd3)} Ra1+ {199.36/81 121} 45. Kc2 {97.44/27 0} Ke2 {199.38/82 34} 46. Re4+ {98.39/28 7} Kf3 {199.40/80 36} 47. Rd4 {98.43/36 32} Ra2+ {199.42/79 194} 48. Kc1 {98.45/41 0} Ra1+ {199.44/81 163 (Ta8)} 49. Kb2 {98.45/38 19} Ra7 {199.46/76 0 (Ta8)} 50. Rd2 {98.51/43 80} Rb7+ {199.48/81 0} 51. Kc2 {98.51/41 28} Rc7+ {199.50/77 0} 52. Nc3 {98.51/41 6} Kg2 {199.52/76 19 (Tc5)} 53. Kb3 {98.51/40 7} Rb7+ {199.54/75 15 (Kf3)} 54. Kc4 {98.51/38 21} Rc7+ {199.56/76 0} 55. Kb4 {98.61/41 38} Rb7+ {199.58/74 0} 56. Nb5 {98.61/39 7} Rb8 {199.62/69 94 (Te7)} 57. Kc4 {98.61/36 7} Rc8+ {199.64/68 31 (Te8)} 58. Kd3 {98.67/39 22} Re8 {199.66/67 0} 59. Ra2 {98.63/37 16 (Sd4)} Re5 {199.66/66 38 (Td8+)} 60. Rb2 {98.67/38 15 (Sd4)} Re8 {199.68/59 19} 61. Nd4 {98.63/38 0} f3 {199.72/55 7} 62. Nf5 {98.67/32 1} Rd8+ {199.74/60 22} 63. Kc4 {98.73/33 9} Kf1 {199.76/59 0} 64. Ng3+ {98.75/31 23 (Se3+)} Kg2 {199.78/58 6} 65. Ne4 {98.79/33 8} Rd7 {199.80/57 28 (Tc8+)} 66. Rb5 {98.79/32 10} Kf1 {199.82/51 0} 67. Rb3 {98.85/35 19} Kg2 {199.86/48 0} 68. Rd3 {98.85/33 10} Rf7 {199.90/50 0 (Te7)} 69. Kd4 {98.85/35 23} Rf8 {199.92/48 39 (Tb7)} 70. Rb3 {98.87/28 13 (Ke3)} Kh3 {199.92/44 7} 71. Ke3 {98.89/34 29} Kh4 {199.94/40 4 (Kg4)} 72. Rb6 {98.95/38 11 (Tb4)} Rf7 {200.00/42 15 (Kg4)} 73. Rf6 {99.69/27 10} Ra7 {200.00/45 24} 74. Kf4 {99.71/31 0} Kh3 {200.00/37 27} 75. Rg6 {99.67/33 24 (Kxf3)} Rf7+ {#33/42 42} 76. Nf6 {99.81/33 0 (Tf6)} Rb7 {#24/51 20 (Ta7)} 77. Nd5 {#24/31 22 (Kxf3)} Rf7+ {#24/44 5} 78. Rf6 {#23/36 19} Rh7 {#21/55 0} 79. Ne3 {#22/37 12 (Kxf3)} Kh4 {#22/53 7} 80. Nf5+ {#21/35 18 (Tg6)} Kh5 {#23/55 11} 81. Ra6 {#20/35 0 (Sg3+)} Rh8 {#19/66 24} 82. Re6 {#19/36 13} Rh7 {#18/33 27} 83. Re7 {#18/35 0} Kg6 {#17/79 11} 84. Rxh7 {#17/36 16} Kxh7 {1/0 0} 85. Kxf3 {2/1 0} Kg6 {2/0 0} 86. Ke4 {1/0 0} Kf6 {1/0 0} 87. f3 {1/1 0} Kg5 {1/0 0} 88. f4+ {2/1 0} Kf6 {2/0 0} 89. Nd4 {1/0 0} Kg6 {1/0 0} 90. f5+ {3/1 0} Kf6 {3/1 0} 91. Kf4 {2/0 0} Ke7 {2/0 0} 92. Ke5 {1/0 0} Kf7 {1/0 0} 93. f6 {2/1 0} Kg6 {2/0 0} 94. Ke6 {1/1 0} Kh6 {1/0 0} 95. f7 {2/1 0} Kg7 {2/1 0} 96. Ke7 {1/0 0} Kh6 {1/0 0} 97. f8=Q+ {4/1 0} Kg5 {4/0 0} 98. Qf3 {3/0 0} Kh4 {3/0 0} 99. Kf7 {2/0 0} Kg5 {2/1 0} 100. Ne6+ {1/1 0 1-0 (100) Crystal 5 KWK-Stockfish Dort 2023 [0.86;1.04]}) 6. Re3 {1.23/41 129} Nb3+ {1.52/42 62} 7. Kb2 {1.27/41 33} h5 {1.63/43 118} 8. Bg7 {1.54/43 0} Kc6 {1.58/44 113} 9. Rxf3 {1.63/41 0} Kb6 {1.83/46 261} 10. Nb8 {1.75/43 8} Rb4 {1.61/45 187} 11. Rxf7 {2.12/42 104 (Tf6+)} Nd4+ {2.53/38 183} 12. Kc1 {2.20/42 0} c3 {2.67/43 474 (Sb5)} 13. Bxd4+ {2.48/44 133} Rxd4 {2.92/41 0} 14. Kc2 {2.61/47 105} Kb5 {3.06/41 0} 15. Kxc3 {2.72/52 69} Rc4+ {3.66/45 390 (Ta4)} 16. Kd3 {3.09/44 72} Rc1 {3.93/41 18} 17. Nd7 {3.17/50 65} Rh1 {4.35/41 3} 18. Rf5+ {3.24/51 134} Kb4 {4.77/41 0} 19. Kd2 {3.80/52 280 (Se5)} Rxh3 {5.15/40 112} 20. Ne5 {4.13/48 0} Kb5 {5.13/39 58} 21. Nd3+ {4.13/50 5} Ka6 {5.17/39 51} 22. Nc5+ {4.13/51 71} Kb6 {5.25/41 0} 23. Na4+ {4.57/44 72} Ka6 {5.15/40 47} 24. Rxh5 {4.57/52 15} Rh1 {5.49/39 77} 25. Nc3 {4.57/42 0} h3 {5.62/32 47} 26. Rh6+ {5.09/44 16} Kb7 {5.66/40 288} 27. Ne4 {5.73/46 0} c6 {5.83/33 35} 28. Rh4 {6.53/46 572} Kb6 {6.17/40 0} 29. Ng5 {7.34/48 149} Rg1 {6.65/35 32 (Th2)} 30. Nxh3 {7.54/36 534} Rh1 {7.07/35 0} 31. Kc3 {8.65/30 97} c5 {6.93/34 246 (Th2)} 32. Rh7 {12.34/34 121} a4 {8.07/33 0} 33. Ng5 {20.66/34 60} Rc1+ {8.74/32 0} 34. Kb2 {79.89/40 32} Rc4 {9.38/33 50} 35. Re7 {79.91/43 17 (Th3)} Rf4 {11.59/35 162} 36. Rf7 {198.15/50 0} Rb4+ {11.61/34 36} 37. Ka3 {198.95/48 40} Kb5 {13.44/28 0} 38. Rf3 {199.09/55 40} Rg4 {11.24/29 0} 39. Ne6 {199.41/54 83 (Sf7)} Rg6 {12.22/25 10} 40. Nc7+ {199.45/56 13 (Te3)} Kc6 {27.11/30 42} 41. Ne8 {199.49/65 0} Rg4 {97.11/26 11} 42. Rf5 {199.53/70 19 (Sf6)} Rd4 {15.06/29 37} 43. Nf6 {199.55/68 0} Kb5 {97.55/29 19} 44. Nd5 {199.57/66 42} Rd3+ {97.57/31 0} 45. Kb2 {199.59/73 32} Kc4 {97.74/32 0} 46. Ne3+ {199.61/72 28} Kb5 {97.88/41 0} 47. Rf4 {199.63/71 171} Kc6 {98.58/39 0 (Td2+)} 48. Kc2 {199.67/66 46} Ra3 {98.58/38 1} 49. Rf6+ {199.69/63 9} Kb7 {98.58/38 23 (Kd7)} 50. Nd1 {199.71/57 8 (Sc4)} Ra2+ {98.64/36 69} 51. Kb1 {199.73/64 0 (Kd3)} Rd2 {14.66/25 5} 52. Nc3 {199.75/62 38 (Sb2)} a3 {98.64/34 6} 53. Ne4 {199.77/53 1} a2+ {98.64/33 8 (Tb2+)} 54. Ka1 {199.83/63 7} Rc2 {98.64/32 1} 55. Rf3 {199.85/50 13} Kb6 {98.64/33 0 (Ka6)} 56. Rc3 {199.87/53 44 (Sc3)} Re2 {98.60/32 16} 57. f3 {199.89/50 0 (Te3)} Kb5 {98.88/40 56} 58. Rxc5+ {199.91/52 0} Kb4 {98.90/40 7} 59. Rc3 {199.93/50 28} Rg2 {98.92/43 0} 60. Rd3 {199.95/45 34 (Te3)} Rh2 {98.94/44 16 (Tc2)} 61. Nd2 {#39/38 3 (Td2)} Rh1+ {98.98/48 11 (Th6)} 62. Kxa2 {#36/44 8} Rh4 {6/1 0 (Th2)} 63. Ne4 {5/0 0} Kc4 {5/0 0} 64. Rb3 {4/1 0} Kd5 {4/0 0} 65. Nc3+ {3/1 0} Kc4 {3/0 0} 66. Ne2 {2/1 0} Rh2 {2/0 0} 67. Rb2 {1/1 0} Rf2 {1/0 0} 68. f4 {8/1 0} Rf1 {8/1 0} 69. Rd2 {7/0 0} Rf2 {7/0 0} 70. Kb2 {6/0 0} Kb4 {6/0 0} 71. Rc2 {5/1 0} Rf3 {5/0 0} 72. Rc7 {4/0 0} Rf2 {4/0 0} 73. Kc2 {3/1 0} Rxe2+ {4/1 0} 74. Kd3 {3/1 0} Rf2 {3/1 0} 75. Ke4 {2/1 0} Re2+ {2/1 0} 76. Kf3 {1/1 0} Re1 {1/0 0} 77. f5 {7/1 0} Rf1+ {7/0 0} 78. Ke4 {6/0 0} Rf2 {6/0 0} 79. Ke5 {5/0 0} Re2+ {5/1 0} 80. Kd4 {4/0 0} Rd2+ {4/1 0} 81. Ke3 {3/1 0} Rd6 {3/1 0} 82. Kf4 {2/1 0} Ra6 {2/0 0} 83. Rf7 {1/1 0} Ra2 {1/0 0} 84. f6 {7/1 0} Kc5 {7/1 0} 85. Rd7 {6/1 0} Rf2+ {6/0 0} 86. Kg5 {5/1 0} Kc6 {5/1 0} 87. Ra7 {4/0 0} Kb6 {4/1 0} 88. Re7 {3/1 0} Rg2+ {3/1 0} 89. Kh4 {2/1 0} Rh2+ {2/1 0} 90. Kg3 {1/1 0} Rh8 {1/0 0} 91. f7 {6/1 0} Rf8 {6/1 0} 92. Kf4 {5/0 0} Kc5 {5/0 0} 93. Ke5 {4/0 0} Rh8 {4/1 0} 94. Re8 {3/0 0} Rh5+ {3/1 0} 95. Kf6 {2/0 0} Rh6+ {2/1 0} 96. Kg5 {1/0 0} Rh5+ {1/0 0} 97. Kxh5 {1/1 0} Kd4 {1/0 0} 98. f8=Q {3/1 0} Kc3 {3/1 0} 99. Re4 {2/0 0} Kd2 {2/0 0} 100. Qc5 {1/0 0} 1-0
[/pgn]