Dev Builds » 20260901-1504

Use this dev build

NCM plays each Stockfish dev build 20,000 times against Stockfish 15. This yields an approximate Elo difference and establishes confidence in the strength of the dev builds.

Summary

Host	Duration	Avg Base NPS	Games	WLD	Standard Elo	Ptnml(0-2)	Gamepair Elo
ncm-dbt-04	00:50:32	573649	500	223 43 234	+130.94 ± 12.76	0 5 63 179 3	+306.84 ± 43.45
			500	223 43 234	+130.94 ± 12.76	0 5 63 179 3	+306.84 ± 43.45

Test Detail

ID	Host	Base NPS	Games	WLD	Standard Elo	Ptnml(0-2)	Gamepair Elo	CLI	PGN
484131	ncm-dbt-04	573649	500	223 43 234	+130.94 ± 12.76	0 5 63 179 3	+306.84 ± 43.45		↓
cutechess-cli \ -rounds 266 \ -games 2 \ -concurrency 16 \ -srand 1014291857 \ -pgnout ncm-dbt-20260901-1504-001.pgn \ -openings \ file=UHO_4060_v2.epd \ format=epd \ order=random \ -repeat \ -resign \ movecount=3 \ score=600 \ -draw \ movenumber=34 \ movecount=8 \ score=5 \ -each \ tc=30+0.3 \ timemargin=10000 \ proto=uci \ option.Hash=128 \ option.Threads=8 \ -engine \ name=20260901-1504 \ cmd=docker \ arg=run \ arg=-i \ arg=--rm \ arg=--entrypoint=/engine \ arg=dev_build:3f6f417b87c0e80ee30914b6b539b4ab7d3b2a5b \ -engine \ name=sf15 \ cmd=docker \ arg=run \ arg=-i \ arg=--rm \ arg=--entrypoint=/engine \ arg=stockfish:15

Host

Base NPS

Games

WLD

Standard Elo

Ptnml(0-2)

Gamepair Elo

CLI

PGN

484131

ncm-dbt-04

573649

500

223 43 234

+130.94 ± 12.76

0 5 63 179 3

+306.84 ± 43.45

↓

Commit

Commit ID	3f6f417b87c0e80ee30914b6b539b4ab7d3b2a5b
Author	Robert Nurnberg @ elitebook
Date	2026-09-01 15:04:52 UTC
Update the WDL model This PR updates the internal WDL model, using data from 2M games played by the revisions since 229f6339e537a097a79831cd06dbfdb3e623d4ac. The normalizing constant decreases significantly from 385 to 304. That means the current 78cp will roughly map to 100cp. ``` > ./updateWDL.sh --firstrev 229f6339e537a097a79831cd06dbfdb3e623d4ac Running: ./updateWDL.sh --firstrev 229f6339e537a097a79831cd06dbfdb3e623d4ac --lasttrev HEAD --materialMin 17 --EloDiffMax 5 started at: Tue 1 Sep 14:31:12 CEST 2026 Look recursively in directory pgns for games with max nElo difference 5 using books matching "UHO_Lichess_4852_v..epd" for SF revisions between 229f6339e537a097a79831cd06dbfdb3e623d4ac (from 2026-08-19 18:48:49 +0200) and HEAD (from 2026-08-29 09:16:46 +0200). Based on 109147283 positions from 2046412 games, NormalizeToPawnValue should change from 385 to 304. In the updated WDL model, 78cp would roughly map to 100cp. ended at: Tue 1 Sep 14:32:20 CEST 2026 ``` ``` > cat scoreWDL.log Converting evals with NormalizeData = {'momType': 'material', 'momMin': 17, 'momMax': 78, 'momTarget': 58, 'as': [-72.32565836, 185.93832038, -144.58862193, 416.44950446]}. Reading eval stats from updateWDL.json. Retained (W,D,L) = (26673519, 54948054, 27525710) positions. Saved distribution plot to updateWDLdistro.png. Fit WDL model based on material. Initial objective function: 0.3550415621263458 Final objective function: 0.3550400701834142 Optimization terminated successfully. const int NormalizeToPawnValue = 304; Corresponding spread = 61; Corresponding normalized spread = 0.19927805405945914; Draw rate at 0.0 eval at material 58 = 0.986853004859315; Parameters in internal value units: p_a = ((-142.721 * x / 58 + 372.352) * x / 58 + -340.711) * x / 58 + 415.235 p_b = ((5.938 * x / 58 + 15.613) * x / 58 + -30.578) * x / 58 + 69.639 constexpr double as[] = {-142.72052667, 372.35176398, -340.71073572, 415.23490212}; constexpr double bs[] = {5.93832785, 15.61267078, -30.57816876, 69.63866711}; Preparing plots. Saved graphics to updateWDL.png. Total elapsed time = 30.92s. ``` The patch only affects the displayed `cp` and `wdl` values, and nothing else. closes https://github.com/official-stockfish/Stockfish/pull/7120 No functional change