In TCEC Reckless has difficulties to mate with rook

[Jouni]

[pgn][Event "TCEC Season 28 - FRD 4 League C"]
[Site "https://tcec-chess.com"]
[Date "2025.10.02"]
[Round "5.1"]
[White "Reckless 0.9.0-dev-b9beffbe"]
[Black "Revenge 20241013"]
[Result "1-0"]
[Annotator "archive"]
[Variant "chess 960"]
[SetUp "1"]
[FEN "rkqrnbbn/pppppppp/8/8/8/8/PPPPPPPP/RKQRNBBN w DAda - 0 1"]
[PlyCount "269"]
[EventDate "2025.??.??"]

1. d4 c5 2. dxc5 Qxc5 3. Nd3 Qc7 4. e4 f6 5. Ng3 e5 6. f4 Ng6 7. Ne2 Nxf4 8.
Nexf4 exf4 9. Nxf4 Bc5 10. Bxc5 Qxc5 11. Qd2 Kc7 12. Qd4 d6 13. g3 Rd7 14. a4
Re7 15. Qd2 Rc8 16. a5 a6 17. Ra4 Kb8 18. Rb4 Ka8 19. b3 Qe5 20. Rd4 Bf7 21.
Qb4 Rc6 22. Nd3 Qh5 23. Rd2 Qg5 24. Re2 Qh5 25. Kb2 Rc8 26. Qb6 Rcc7 27. Rf2
Qb5 28. Nb4 Qd7 29. Rfd2 Qc8 30. Bg2 Re5 31. c4 h6 32. Nd3 Rg5 33. Re2 Rc6 34.
Qb4 Qb8 35. h4 Rxg3 36. Qe1 Qa7 37. c5 Rxd3 38. Rxd3 Rxc5 39. Rc3 Rc7 40. Rxc7
Nxc7 41. Qc3 Nb5 42. Qc8+ Qb8 43. Bh3 Qxc8 44. Bxc8 Nc7 45. Rg2 g5 46. Rf2 Kb8
47. Rxf6 Kxc8 48. Rxf7 gxh4 49. Rh7 Nb5 50. Rxh6 Kd7 51. Rxh4 Kc6 52. Rh7 Na7
53. Kc3 Nb5+ 54. Kc4 Na3+ 55. Kc3 Nb5+ 56. Kd3 Na3 57. Rh6 Kd7 58. Kd4 Nc2+ 59.
Kc4 Ne3+ 60. Kd3 Ng4 61. Rh7+ Kc6 62. Re7 Nf6 63. b4 Ng4 64. Kd4 Nh2 65. Rf7
Ng4 66. Rf5 Kd7 67. b5 axb5 68. Rg5 Nf6 69. Rxb5 Kc6 70. Rb6+ Kc7 71. e5 dxe5+
72. Kc4 Ne4 73. Kd5 Nd2 74. Rb2 Nf3 75. Kc5 Ng5 76. Rc2 Kb8 77. Kb6 Ne4 78. a6
bxa6 79. Kc6 Ka7 80. Re2 Ng5 81. Rxe5 Nf3 82. Re7+ Kb8 83. Kd5 a5 84. Rf7 Ne1
85. Kc6 Nd3 86. Rf5 Nb4+ 87. Kb6 Kc8 88. Rxa5 Kd7 89. Rb5 Nc2 90. Rb2 Ne3 91.
Rd2+ Kc8 92. Kc6 Ng4 93. Re2 Kd8 94. Re6 Nf2 95. Kd6 Kc8 96. Re8+ Kb7 97. Re2
Nd1 98. Kc5 Nc3 99. Re3 Nd1 100. Rf3 Ka6 101. Kb4 Kb6 102. Kb3 Kc5 103. Kc2 Nb2
104. Kxb2 Kd4 105. Rf5 Ke4 106. Rh5 Kd4 107. Rh6 Kc5 108. Kc3 Kd5 109. Kd3 Ke5
110. Kc4 Kf5 111. Kd4 Kg5 112. Rh7 Kg6 113. Ra7 Kf5 114. Kd5 Kf4 115. Kd4 Kf5
116. Ke3 Ke5 117. Kf3 Kd5 118. Kf4 Kd6 119. Rf7 Kd5 120. Rf6 Kc4 121. Ke5 Kc3
122. Rd6 Kc4 123. Kf4 Kc5 124. Rd8 Kc6 125. Ke5 Kb5 126. Kd4 Kb6 127. Kd5 Kc7
128. Rd6 Kb7 129. Rc6 Kb8 130. Kd6 Kb7 131. Kd7 Kb8 132. Rb6+ Ka8 133. Kc7 Ka7
134. Re6 Ka8 135. Ra6# 1-0

[/pgn]

512 threads and 7 piece tablebases .

[Steve Maughan]

There must be some sort of bug. An engine of this strength should be able to find the mate simply using search and without any special endgame knowledge.

[Jouni]

Looking at the game Reckless makes millions tablebase accesses with 7-4 pieces. Is it necessary? Only with 3 pieces it has about 20 accesses.No tablebases and move 100:

Analysis by Reckless 0.8.0:
...
100.Rg3 Nf2 101.Kd4 Kc6 102.Rg2 Nh3 103.Ke3 Kd5 104.Rg3 Nf2 105.Rg5+ Ke6 106.Kxf2 Kf6 107.Ra5 Ke6 108.Kf3 Kd6 109.Ke4 Ke6 110.Ra6+ Ke7 111.Kd5 Kf7 112.Ke5 Ke7 113.Ra7+ Kd8 114.Kd6 Ke8 115.Rc7 Kf8 116.Ke6
+- (#20) Depth: 33/41 00:00:15 283mN