TCEC15: the 15th Top Chess Engine Championship Guy Haworth1 and Nelson Hernandez Reading, UK and Maryland, USA TCEC Season 15 started on March 5th 2019 with a more liberal Division 4 featuring several engines in their first TCEC season. At the top end, interest would centre on whether the recent entries, ETHEREAL, KOMODO MCTS and LEELA CHESS ZERO would again improve their already impressive performances. Fig. 1 and Table 1 provide the logos and details on the enlarged field of 44 engines. DP D1 D2 D3 D4 Fig. 1. Logos for the TCEC 15 engines (CPW, 2019) as in their original divisions. There were a few nudges to the rules. In the event of network breaks, if both engines were in the 7-man and/or TCEC win (or draw) zone, the game was adjudicated as a win (or draw). Otherwise, TCEC resumed games with extra initialisation time rather than restart them. The common platform for TCEC15, as for TCEC14, consisted of two computers. One was the estab- lished, formidable 44-core server of TCEC11-14 (Intel, 2017) with 64GiB of DDR4 ECC RAM and a Crucial CT250M500 240 GB SSD for the EGTs. The ‘GPU server’, upgraded to a Quad Core i5 3570k with 32GiB DDR3 RAM, sported Nvidia (2018) GeForce RTX 2080 Ti and 2080 GPUs. 1 Corresponding author: [email protected] Table 1. The TCEC15 engines (CPW, 2019), details, authors and progress. Engine Initial proto- Hash Countr Final # thr. EGTs Authors ab Name Version ELO Div. col Kb y Codes Div. 01 AS AllieStein v0.1-n4 2557 4b 3 uci 7,168 — Adam Treat and Mark Jordan US ↗↗ ↗↗P 02 An Andscacs 0.95123 3469 1 43 uci 8,192 — Daniel José Queraltó AD →1 03 Ar Arasan TCEC15 3290 3 43 uci 16,384 Syz. Jon Dart US →3 04 Ba Bagatur 1.5f 2496 4b 43 uci ? — Krasimir Topchiyski BG ↘ 5 05 Bo Booot 6.3.1 3407 2 32 uci 16,384 — Alex Morozov UA →2 06 Ch Cheese 2.0 2740 4a 8 uci 16,384 — Patrice Duhamel FR →4 07 Cb ChessbrainVB 3.72 3342 2 43 xboard 1,200 — Roger Zuehlsdorf DE →2 08 c22 chess22k 1.12 2970 4b 43 uci 16,384 — Sander Maassen vd Brink NL →4 09 Ch Chiron 230119 3411 1 43 uci 16,384 Syz. Ubaldo Andrea Farina IT ↘ 2 10 Et Ethereal 11.38 3483 P 43 uci 16,384 Syz. Andrew Grant US ↘ 1 11 Fi Fire 11819 3488 P 43 uci 16,384 Syz. Norman Schmidt US ↘ 1 12 Fz Fizbo 2 3419 1 43 uci 16,384 Syz. Youri Matiounine US →1 13 Fr Fritz 16.10 3319 2 43 uci 16,384 Nal? Vasik Rajlich CZ/US ↘ 3 14 Ga Gaviota 1.01 2653 4b 43 uci 16,384 Gav. FM Miguel Ballicora ES →4 15 Gi Ginkgo 2.18 3440 2 43 uci 16,384 Syz. Frank Schneider DE →2 16 Gu Gull 3 3300 3 43 uci 16,384 — Vadim Demichev RU →3 17 Ho Houdini 6.03 3571 P 43 uci 16,384 Syz. Robert Houdart BE →P 18 Ig Igel 1.2 2412 4a 43 uci 16,384 — Volodymyr Shcherbyna UA ↘ 5 19 Jo Jonny 8.1 3400 1 43 uci 16,384 Syz. Johannes Zwanzger DE ↘ 2 20 Ju Jumbo 0.6.99.2 2738 4b 43 xboard 16,384 Gav. Sven Schüle DE ↘ 5 21 Ko Komodo 2306.00 3486 P 43 uci 16,384 Syz. Don Dailey, Larry Kaufman, US →P 22 Km Komodo MCTS 2301.00 3487 1 43 uci 16,384 Syz. Mark Lefler US ↗P 23 La Laser 230319 3444 1 43 uci 16,384 Syz. Jeffrey An, Michael An US →1 24 Lc LCZero v0.21.1-n41800 3603 P 3 uci — Syz. UCT/NN AI Community — →P 25 Ma Marvin 20190228 2678 4b 43 uci 16384 Syz. Martin Danielsson SE →4 26 Mi Minic 0.42 2872 4a 40 xboard 16384 — Vivien Clauzon FR →4 27 Mo Monolith 1 2617 4b 16 uci 16384 Syz. Jonas Mayr AT →4 28 Ne Nemorino 5.08 3247 4a 43 uci 16,384 Syz. Christian Günther US ↗↘ 4 29 Ni Nirvana 2.4 3343 2 32 uci 16,384 — Thomas Kolarik US ↘ 3 30 Pe Pedone 1.9 3285 3 43 uci 16,384 Syz. Fabio Gobbato IT ↘ 4 31 pi pirarucu 2.9.5 3124 4b 43 uci 4,096 — Raoni Campos BR →4 32 Ro Rodent III 0.276 2958 4a 16 uci 4,096 — Pawel Koziol PL →4 33 rf rofchade 2.016T 3290 3 43 uci 16,384 Syz. Ronald Friederich NL ↗ 2 34 Ru RubiChess 1.3.1 3200 4a 43 uci 16,384 Syz. Andreas Matthies DE →4 35 Sn ScorpioNN 2.9.0 2325 4b — xboard — — Daniel Shawl ET →4 36 St Stockfish 19040612 3603 P 43 uci 16,384 Syz. Tord Romstad, Marco Costalba, NO/IT/ →P 37 Te Texel 1.08a13 3210 3 43 uci 16,384 Syz. Peter Österlund SE →3 38 Tb The Baron 3.44.1 2987 4a 42 uci 16,384 Syz. Richard Pijl NL →4 39 To Topple 0.4.0 2615 4a 43 uci 16,384 Syz. Vincent Tang UK ↘ 5 40 Tu Tucano 7.07 2996 4a 43 xboard 16,384 — Alcides Schulz BR →4 41 Va Vajolet2 2.6.1 3240 3 43 uci 16,384 Syz. Marco Belli IT →3 42 Wa Wasp 3.59 3101 4b 43 uci 8,192 Syz. John Stanback US →4 43 Wi Winter 0.5 2868 4a 43 uci 16,384 — FM Jonathan Rosenthal CH →4 44 Xi Xiphos 0.5.2 3449 2 43 uci 16384 Syz. Milos Tatarevic RS ↗ 1 Initial interest centred on a third non-Shannon engine, this time the hybrid ALLIESTEIN, a cross between Adam Treat’s ALLIE and Mark Jordan’s LEELENSTEIN (Chessdom, 2019) and a pupil of supervised rather than ‘tabula rasa’ learning. Would this combine the best of ‘Shannon AB’ and neural-network approaches in a case of ‘1+1=3’ or would it be a fall between two stools? There were several reasons for believing that ALLIESTEIN would not tarry in Division 4 for too long. HANNIBAL was recuperating after its crashes in TCEC14 but new to TCEC were some other ‘AB conventional’ engines – CHEESE, BAGATUR, IGEL, JUMBO, MARVIN, MINIC, MONOLITH, RUBICHESS and TOPPLE – a generous addition to the line-up. Given the wide range of estimated ELOs, there was likely to be a higher degree of carnage in Division 4 and so it proved. The division was in fact split into two halves with a play-off for the promotion places between the top two in each half. 1 Division 4a/b: each half of 1 DRR, 2 RRs, 18 rounds, 90 games @ 30+5/m As for TCEC12-14, each engine played both White and Black from four-ply openings defined by the second author here. The results are as in Tables 2-3: ‘P%’ is the %-score and ‘ELO’ the change to the engine’s nominal ELO based on its performance. Generic stats are in Tables 11 and 12. In part 4a, CHEESE’s win ‘against the otherwise unchallenged NEMORINO in game 11.2/52 was a clear outlier. RUBICHESS took second by virtue of its 2-0 result against WINTER. In Act 2 game 12.5/60, SCORPIONN had a 7-man win (dtm = 22m) on move 80 but took 108 moves to get a 6-man EGT result. WASP disconnected against ALLIESTEIN in game 15.4/74, effectively a 1.5- point swing for second place as ‘crashes’ are the first tie-breaker. Unusually, games 29 and 87 ended in mate, and SCORPIO exhibited its ‘resigns’ move in games 5, 28 and 78. The network crashed in g32, ALLIESTEIN–CHESS22K, on move 49w with CHESS22K’s evaluation at +5.3, a clear case for a continuation rather than a restart, surely the default response. ALLIESTEIN worked through to a 6-man RB-BP ‘mate in 18’ win with some difficulty. It would have been interesting to see it actually achieve this as neither engine was using the 6-man endgame tables (de Man, 2018). Table 2. The TCEC15 Division 4a cross-table: one DRR phase, 18 rounds, 90 games. # Engine ELO Pts P% Elo ± SB Ne Ru Wi Ro Tb Tu Ch Mi To Ig 01 Nemorino 5.08 3242 15.0 83.3 -9 120.00 11 1= 1= 11 =1 =0 11 11 11 02 RubiChess 1.3.1 3039 12.5 69.4 0 90.25 00 11 == =0 1= 11 11 11 1= 03 Winter 0.5 2911 12.5 69.4 25 92.75 0= 00 10 11 =1 =1 11 11 11 04 Rodent III 0.276 2980 11.0 61.1 -3 82.50 0= == 01 =1 01 10 =1 =1 11 05 The Baron 3.44.1 2943 10.5 58.3 -1 71.25 00 =1 00 =0 1= 1= 11 11 =1 06 Tucano 7.07 2966 9.5 52.8 -15 64.75 =0 0= =0 10 0= =1 10 11 11 07 Cheese 2.0 2827 8.0 44.4 -1 62.75 =1 00 =0 01 0= =0 01 10 11 08 Minic 0.42 2677 5.0 27.8 0 30.25 00 00 00 =0 00 01 10 10 1= 09 Topple 0.4.0 2589 3.5 19.4 0 21.00 00 00 00 =0 00 00 01 01 10 10 Igel 1.2 2521 2.5 13.9 1 17.50 00 0= 00 00 =0 00 00 0= 01 Table 3.