Blizzard v0.4

+186 Elo over 0.3. In a 200-game match Blizzard 0.4 scored +117 =64 −19 (74.5%), with a 95% interval
of +146 to +231 Elo. Both engines had 0.2 s per move and played book openings, each opening with both colors.
Against Stockfish 2800 it now scores 61%, up from 47% for 0.3.

What's new

Twice the search-scored training data. The network keeps the same shape as in 0.3 (3072 → 2×128 → 1,
king-aware inputs), but it was fine-tuned on 6.6 million positions scored by a short Stockfish 19 search,
up from 3 million. Its error was checked on 30,000 positions it never saw in training.

A faster network. Accumulator updates and the output layer now run on WebAssembly SIMD, eight numbers
per instruction, both in the browser and in the UCI engine. That is 30–45% more positions per second,
with exactly the same evaluations as the plain JavaScript path, which is still there as a fallback.

Search.

• Correction history: the static evaluation is adjusted by how far off it was in earlier positions with
  the same pawn structure.
• Capture history orders captures by how well they worked before.
• Continuation history now also looks at the move two plies back.
• With a fixed time per move (go movetime), the engine uses the whole time.

On their own the search changes were worth about +60 Elo against 0.3; with the new network, +186.

Strength

Match	Games	Score	Elo difference (95% interval)
0.4 vs 0.3	200	74.5%	+186 (+146 to +231)
0.4 vs Stockfish 2800	40	61% (0.3 scored 47%)	+80 (−17 to +190)
0.4 vs Stockfish 3000	40	26% (0.3 scored 20%)	−179 (−290 to −95)

Stockfish 19 here is the single-threaded browser build, limited with UCI_Elo. These are not FIDE or
CCRL ratings; they compare Blizzard versions under the same conditions.

Downloads

File	For	SHA-256
blizzard-0.4-windows.zip	Windows 10/11, 64-bit, nothing to install	004ad177d94243cda4171bf49caea5bd948dda34bc6d7a911e8b72e6edc59dcb
blizzard-0.4-universal.zip	macOS, Linux and others, needs Node.js 18+	119aaeee499cd0bf9e42b35e4023ae939300313c215ba61b0ad64bab5baab5dd

Unpack, then add blizzard.exe (or node blizzard-uci.js) to Arena, Cute Chess, En Croissant or any
other UCI program.

Upgrading from 0.3

• Replace the old files. UCI options are unchanged.
• UseNNUE false still switches to the hand-written evaluation.
• The engine still loads 0.2 and 0.3 networks.
• blizzard.exe is not code-signed: if SmartScreen warns, click More info, then Run anyway.