Wordfish-5.20-040826

• Release name: Wordfish-5.20-040826.
• UCI identity: id name Wordfish-5.20-040826.
• Canonical post-R7 source merge: 33636985d23bcaabe60e6293aa1f5157d0d7a80a.
• Architecture-aware Windows executable: Wordfish-5.20-040826-sse41popcnt.exe.
• Architecture-aware GUI / analysis banner: Wordfish-5.20-040826-sse41popcnt.
• Maintainer and UCI author identity: Jorge Ruiz, together with the Stockfish developers credited by the project.
• Default NNUE: nn-ab28990d4ea3.nnue.
• NNUE SHA-256: ab28990d4ea3d5c97f7d3918bc5dd5061609330369fe00c2d93a34d4777b5552.
• Public small-net option: EvalFileSmall remains absent.

• Public identity retained: Wordfish-5.20-040826. No artificial version bump was introduced solely to reflect the reconstruction work.
• Exact Stockfish authority: stockfish-dev-20260803-762dd1da, SHA 762dd1da9a5db458180b2c5db6c53dc40ec61e1a.
• Final canonical Wordfish merge after R7: 33636985d23bcaabe60e6293aa1f5157d0d7a80a.
• Reconstruction invariant: if the protected Wordfish overlay is conceptually removed, the remaining Stockfish-derived engine source is semantically equivalent to the exact target.
• Protected overlay retained: Experience, Book1/Book2, Wordfish_zobrist.h compatibility, MCTS/MonteCarlo, sparsehash, lichess tablebase extensions, Syzygy, Contempt, King Safety and Wordfish UCI identity.
• Current NNUE: nn-ab28990d4ea3.nnue, with the common NNUE source subtree reconstructed to exact target.

- Release boundary: 12 June 2026
- Main role: strict single-net closure plus selected Stockfish-dev work through June 10
- Default NNUE: nn-71d6d32cb962.nnue
- Public NNUE option: EvalFile
- EvalFileSmall: absent
- Major documented corrections:
  FEN pawn-rank validation
  HalfKA / Threats accumulator merge
  TT depth underflow protection
  L3 / NUMA topology
  atomic do_move / material-key correction
- Release identity:
  Wordfish-5.0-120626
- The old page did not include the later June, July or August topology blocks
- The old page did not include the final MSYS2 CLANG64 PGO validation

- Public release identity remains: Wordfish-5.20-040826
- Exact upstream authority: stockfish-dev-20260803-762dd1da
- Exact target SHA: 762dd1da9a5db458180b2c5db6c53dc40ec61e1a
- Default NNUE: nn-ab28990d4ea3.nnue
- Public NNUE option: EvalFile
- EvalFileSmall: still absent
- June–August chronological work retained
- Full R6 target-tree reconstruction completed after chronological integration
- 21/21 common NNUE source files aligned byte-for-byte with target
- target search / position / history / TT / memory / thread / NUMA topology restored
- Wordfish Experience / Book / Zobrist / MCTS / Contempt / King Safety rebased and preserved
- R7 removed the last unnecessary attacks.h compatibility layer
- canonical post-R7 merge: 33636985d23bcaabe60e6293aa1f5157d0d7a80a
- maintainer GUI replay confirms corrected choices in previously problematic lost-game positions

Interpretation: Wordfish 5.0 established the June strict single-net and correctness baseline. Wordfish 5.20 retains that baseline and the same public release identity, but the source authority has now been closed against the exact August target rather than inferred from chronological patch coverage alone. The decisive change is the removal of the remaining hybrid upstream-derived state and the rebase of the Wordfish overlay onto the final Stockfish target skeleton.

The following table records both the chronological integration phases and the later forensic recovery sequence that closed the exact-target gaps. The R6 reconstruction is the decisive source-authority step: chronology alone was no longer accepted as proof of equivalence. The labels are repository phase identifiers, not Elo claims.

• Active network: nn-ab28990d4ea3.nnue.
• Network generation: the current tree contains the later NNUE feature topology associated with the July 20 SFNNv16 phase and the July 26 network update.
• Public runtime selector: EvalFile.
• Strict single-net rule: EvalFileSmall remains absent and the retired dual-network runtime surfaces remain excluded.
• Runtime verification: the validated binary reported NNUE evaluation using nn-ab28990d4ea3.nnue.
• Shared-memory verification: the first network replica initialized through shared memory during the runtime smoke test.

• Exact-target reconstruction supersedes patch-count confidence: the final audit compared the complete Wordfish and Stockfish trees and rebuilt stale/hybrid Stockfish-derived areas from the exact 762dd1da target before reapplying the Wordfish overlay.
• Evaluation-sensitive source closure: the complete common NNUE subtree, final network API, target search skeleton, position-state pipeline, histories and TT semantics were aligned as one coherent target state rather than as isolated historical hunks.
• Network authority changed several times during the audited chronology: the June nn-71d6d32cb962.nnue authority was superseded by later June and July networks, ending with nn-ab28990d4ea3.nnue.
• SFNNv16-era feature topology: PP_3Wide, revised FullThreats dimensions and related accumulator/architecture surfaces are now represented.
• Later SIMD work: the tree includes the required AVX-512 ICL and dense VNNI antecedents, paired-activation work and later platform-specific NNUE paths.
• Move generation and attacks: RankAttacks and dual-hyperbola surfaces were normalized further, with later compile-time and lookup-table refinements.
• Search chronology: the July blocks include upstream search-formula, pruning, history and negative-extension evolution, including the explicit reversion of the temporary dynamic NMP change.
• Version integrity: the build system tracks a dirty source tree through the GIT_DIFFINDEX marker while preserving a clean release identity after commit.
• Shared memory: the August blocks advance Unix shared-memory ownership and lifecycle handling, verify memfd_create support and prevent SIGPIPE termination when a client disconnects.
• Windows CLANG64 compatibility: the Win32 include topology was corrected so windows.h supplies the declarations required by shellapi.h.

The exact-target reconstruction and final attacks normalization were validated separately from the earlier P8S Windows profile-build evidence. No ARM matrix is part of this closure.

• R6 GCC BMI2: build passed.
• R6 GCC AVX2: build passed.
• R6 Clang BMI2: build passed in the available environment.
• R6 runtime: UCI, readiness, bench, depth-8 search, NNUE loading, Experience, Book, MCTS and Threads>1 smokes passed.
• R7 GCC BMI2: build passed after removing the global attacks aliases.
• R7 GCC AVX2: build passed, confirming the DualHyperbola/RankAttacks path remained healthy.
• R7 King Safety regression: non-default King Safety search completed normally.
• R7 PolyBook regression: an en-passant book key position exercised the explicit Attacks::attacks_bb<PAWN>() path successfully.
• Final attacks API: src/attacks.h is byte-identical to the exact Stockfish target.
• GUI regression: the maintainer replayed previously problematic lost-game positions and confirmed corrected move choices in those tested positions.

The P8S-era 5.20 tree was compiled locally on Windows 10 under MSYS2 CLANG64 using the project’s Clang/MinGW-w64 route. This remains valid platform evidence for the corrected _WIN32 include path and the SSE4.1/POPCNT PGO workflow. It predates the later R6/R7 full source reconstruction and is therefore recorded here as historical platform evidence rather than as a claim that the post-R7 tree has already repeated the same local PGO run.

make -j profile-build \
  ARCH=x86-64-sse41-popcnt \
  COMP=clang \
  EXTRALDFLAGS="-fuse-ld=lld"

Step 1/4 — instrumented executable: PASS
Step 2/4 — benchmark and profile collection: PASS
Step 3/4 — optimized executable using profile data: PASS
Step 4/4 — profile-data cleanup: PASS

Instrumented benchmark:
Nodes searched : 2471425
Nodes/second   : 248984

Final executable:
Wordfish-5.20-040826-sse41popcnt.exe

Warning gate        : PASS
Compiler error gate : PASS
Linker blocker gate : PASS

Before P8S, src/misc.cpp included shellapi.h before windows.h. Under the current MSYS2 CLANG64 headers, that left declarations such as DECLARE_HANDLE and EXTERN_C unavailable when shellapi.h was parsed.

Correct final order:

#include <direct.h>
#include <windows.h>
#include <shellapi.h>

Result at P8S: the same source file that previously stopped the profile build compiled in both the instrumented and profile-use stages. R6 later reconstructed misc.cpp against the exact target while preserving the required Windows include order and Wordfish identity.

Wordfish-5.20-040826-sse41popcnt
id name Wordfish-5.20-040826
id author Jorge Ruiz and the Stockfish developers (see AUTHORS file)
uciok
readyok

option name EvalFile type string default nn-ab28990d4ea3.nnue
info string NNUE evaluation using nn-ab28990d4ea3.nnue
info string Network replica 1: Shared memory.
info string Using 1 thread
bestmove a2a3

Interpretation: the release identity, network authority and architecture suffix are not inferred from filenames alone. They were observed in the executable’s own UCI and runtime output.

The Stockfish-derived chronology did not remove the accepted Wordfish extensions. The final UCI inspection confirmed the following families:

• Experience: enable/disable, file, read-only mode, book mode, width, evaluation importance, depth range, move limit, status and synchronization.
• Opening books: Book1 and Book2, each with file, best-move, depth and width controls.
• Syzygy: path, probe depth, 50-move rule and probe limit.
• MCTS / MonteCarlo: search-strategy selection, enable switch, rollout depth, simulations and exploration controls.
• Standard controls: Threads, Hash, Ponder, MultiPV, skill, time-management controls, Chess960 and UCI strength limiting.
• NNUE: one public EvalFile authority and no EvalFileSmall.

The current release page distinguishes source authority from binary evidence. The historical P8S validation directly certifies the previously built Windows SSE4.1/POPCNT PGO executable; it must not be silently promoted to post-R7 binary evidence. Binaries produced from the corrected R7 source tree should be listed publicly only after their own compilation logs and filenames have been checked.

Previously evidenced P8S binary:
Wordfish-5.20-040826-sse41popcnt.exe

Required package rule:
- Build only from the accepted Wordfish-5.20-040826 source tree.
- Preserve the current NNUE authority.
- Do not patch source code during package generation.
- Include only binaries with successful compilation and clean logs.
- Record architecture-specific filenames and SHA-256 checksums.
- Do not claim an untested target merely because it exists in the Makefile.

The current source chronology does not reverse the strict single-net work inherited from Wordfish 4.90 and Wordfish 5.0. The following retired public or adapter surfaces remain outside the accepted runtime model:

EvalFileSmall
EvalFileDefaultNameSmall
NetworkSmall
SmallNetworkArchitecture
SmallFeatureTransformer
NNUE::Networks dual holder
active_network(...)
active_cache(...)
singlenet_adapter
onVerifyNetworks
load_networks(...)
verify_networks(...)
accumulatorSmall
caches.small / caches.big
networks.small / networks.big

• Supported: the current Stockfish-derived source is closed against the exact target 762dd1da9a5db458180b2c5db6c53dc40ec61e1a, not merely against a checklist of historical commits.
• Supported: the maintainer’s GUI replay of previously problematic lost-game positions no longer reproduces the former bad move choices and the corrected build proposes the expected continuations.
• Supported: the default network is nn-ab28990d4ea3.nnue, not the former nn-71d6d32cb962.nnue.
• Supported: the previously documented P8S Windows SSE4.1/POPCNT PGO build completed under MSYS2 CLANG64 without warning, compiler-error or linker-blocker findings.
• Supported: that P8S executable initialized UCI, loaded the NNUE, used a shared-memory network replica and returned a legal move; the later R6/R7 tree has its own targeted build and runtime evidence listed above.
• Not supported: attributing every former lost game to one isolated evaluation formula or one single source line. The forensic evidence identifies a broader hybrid source state, and the corrective action reconstructed all affected target-derived subsystems.
• Not supported: a guaranteed Elo increase over Wordfish 5.0. Strength requires controlled match evidence.
• Not supported: a universal speed increase on every processor. The chronology includes correctness, architecture, cleanup and platform changes as well as performance-oriented changes.
• Not supported: production-grade MCTS behaviour.
• Not supported: automatic certification of every Makefile target or every binary that may later be added to a ZIP.

Wordfish-5.20-040826 keeps the same release ID, but its accepted source authority is now materially stronger than in the previous page revision. The final work did not stop at chronological Stockfish-dev integration: the complete tree was compared against exact target 762dd1da9a5db458180b2c5db6c53dc40ec61e1a, stale/hybrid Stockfish-derived areas were reconstructed, and the Wordfish overlay was rebased on top. R6 closed the full source tree; R7 removed the last unnecessary global attacks compatibility layer while preserving PolyBook and King Safety through explicit target API calls. The current tree retains Experience, Book1/Book2, Wordfish Zobrist compatibility, MCTS/MonteCarlo, Syzygy, lichess tablebase extensions, sparsehash, Contempt, King Safety and the strict single-net model with nn-ab28990d4ea3.nnue. The maintainer’s GUI regression replay of previously lost/problematic games confirms that the corrected engine no longer reproduces the earlier erratic move choices in those tested positions. This closes the observed correctness defect while leaving Elo/strength conclusions to controlled match evidence.