IJCCRL Elite Original Chess Engines bullet tournament

The current IJCCRL Blitz Chess Engines Rating List is now based on a renewed Elite Original Engines tournament configuration, aligned with our 2025 Cup Season IJCRL NNUE Bullet Elite framework. This cycle replaces the previous setup while preserving the same methodological rigour and emphasis on independently-developed, author-maintained engines. The event is conducted with cutechess-cli under the label “Cup season Ijcrl 2025”, and is hosted on a dedicated local test bench rather than a shared or virtualised environment.

The present elite tournament includes the following original engines and binaries:
Alexandria 8.1.12 AVX2, Berserk 13 AVX2-PEXT, Dragon 3.3 64-bit, Integral AVX2, Lc0, Obsidian 1.60 AVX2-PEXT, PlentyChess 7.0.0 FMA, Stockfish x86-64 AVX2, and Caissa 1.23 x64 AVX2. Each engine is run with the official or author-recommended AVX2 / PEXT / FMA3-optimised binary where available, ensuring that modern CPU features are used consistently while keeping the playing conditions comparable across the field. All engines use 1 search thread and a fixed 32 MB hash allocation, so that scalability differences in multi-threading do not distort the resulting ratings.

The tournament itself is a round-robin competition managed by cutechess-cli, with multiple full cycles to reduce statistical noise. Pairings are generated as a round-robin with colour-reversed games (-tournament round-robin -games 2), and the schedule is extended over 15 rounds with repeated cycles (-rounds 15) to accumulate a substantial number of games for rating purposes. The option -repeat 2 is used in conjunction with the opening file so that each starting position is played twice with colours swapped, enhancing fairness and reducing opening-bias. Intermediate Elo estimates are produced at regular intervals (-ratinginterval 10), though final ratings for publication are computed only once all games have been completed and thoroughly checked.

All games start from curated positions taken from the UHO_2024_8mvs_big_+100_+119 suite, supplied as a PGN file
..\Openings\PGN\UHO_2024_8mvs_big_+100_+119.pgn. These balanced, human-curated positions are served in random order (order=random) and are designed to avoid heavy opening-book theory, early repetition, and trivial drawing lines. By forcing engines into rich middlegame structures after eight moves, the tournament focuses on search and evaluation quality rather than book preparation. The option -maxmoves 200 ensures that excessively long endgames are adjudicated consistently, avoiding pathological marathons that could bias the statistics.

Endgame play is further standardised by enabling Syzygy tablebases (-tb C:\Syzygy -tbpieces 6). This configuration gives all engines access to up to 6-man Syzygy bases, ensuring perfect play in a wide class of endings and avoiding arbitrary adjudication. Tablebase access is identical for every participant, so any residual differences in endgame performance reflect the engines’ search strategies and evaluation heuristics rather than unequal access to external data.

A key innovation in the current cycle is the hardware platform. The entire tournament is run on a modern mobile high-performance system based on an
AMD Ryzen 7 8745HS processor, paired with 32 GB of DDR5 RAM and a 1 TB NVMe SSD. This configuration offers high single-thread performance, excellent memory bandwidth, and very low I/O latency. The use of an NVMe SSD essentially eliminates storage bottlenecks when accessing Syzygy tablebases and opening files, while DDR5 memory reduces the risk of bandwidth saturation in hash-intensive positions. By fixing the hardware in this way and avoiding background tasks, IJCCRL ensures that the resulting ratings are stable, reproducible and directly attributable to engine strength rather than to operating-system noise or resource contention.

All games from the event are saved to a single PGN archive
(..\Games\games.pgn) for independent verification and future research. Ratings derived from this tournament feed directly into the bullet Chess Engines Rating List, where they are processed using established Elo calculation tools and published alongside confidence intervals and auxiliary statistics. In this way, the updated configuration preserves the tradition of IJCCRL’s earlier elite tournaments while taking full advantage of contemporary hardware and NNUE-optimised binaries, offering readers and subscribers a transparent and methodologically sound benchmark of today’s strongest original engines.