Playing strength: a transfer from foreign ratings, and IMS
A transfer from foreign ratings, followed by IMS Internally measured strength: 2200 plus the Elo difference against a frozen reference configuration of our own. A progress measure between our versions, not a rating from a ranking list. as a measure of progress between our own versions.
Transferred playing strength
Coherent 0.1.58: approximately 2300 ± 60 — transferred over 2 opponents that disagree with each other.
published rating + measured difference
The two measurements
| Opponent | Published rating | Games | Score rate | Measured difference | Anchored Coherent |
|---|---|---|---|---|---|
| Blunder 7.1.0 | 2388 ± 18 | 548 | 41.88 % | −56.93 ± 28.02 | 2331 ± 33 |
| Drofa 2.0.0 | 2420 ± 19 | 600 | 30.50 % | −143.07 ± 26.28 | 2277 ± 32 |
All error figures are half-widths at the 95% level.
The two answers lie 54 points apart: 2.28 standard deviations; the two-sided chance probability is 0.022.
This is a transfer, not a place in a ranking. A shared error in transferring the ratings could shift both anchors in the same direction and is not covered by the published band.
Blunder 7.1.0 against Drofa 2.0.0 directly in our own setup: completed.
The two anchors play each other directly in our setup
| Property | Value |
|---|---|
| Games | 442 |
| Pairs | 221 |
| Pentanomial (Blunder) | 68 / 49 / 65 / 28 / 11 |
| Score rate (Blunder) | 34.73 % |
| Measured difference | 109.6 ± 30.1 |
| Difference from the ranking list | 77.6 |
Explanation 1 confirmed: published ratings do not transfer to our conditions. The measured gap is more than three times the one in the ranking list.
Measured in two parts (200 and 242 games, different book positions); part 2 was ended early on the operator's instruction, the games played remain valid. Merged at pair level, not across the two Elo Strength difference to the opponent, estimated from the games, with a 95-percent half-width where the oracle reported one. Never an absolute rating. estimators.
Blunder 7.1.0: The run against Blunder ended at game 549 because the opponent crashed and the tournament manager stopped there. The aborted game is not counted.
Measurement conditions of the two anchorings
| Property | Value |
|---|---|
| Time control | 120+1 |
| Opening book | 8moves_v3 · 34,700 positions |
| Hash (MB per side) | 64 |
| Concurrent games | 4 |
| Adjudication | none |
| Procedure | fixed number of games, no early stop |
Data delivery created on 2026-09-07 · Measurements, interpretation and limitations
The engines Blunder 7.1.0 and Drofa 2.0.0 are named by word mark and version because the measurement conditions require it; no connection to their authors and no endorsement by them exists.
IMS says how the engine fares against a frozen reference configuration of its own — and nothing else. Anyone who wants to know where the program stands in the field needs opponents that somebody else built and that somebody else rated.
IMS lies above both anchors. As a measure of progress between versions of our own it remains usable; as a statement about strength in the field it was too optimistic.
There is no conversion between IMS and Elo, no shared axis and no shared chart with two scales.
IMS — internal progress
IMS = 2200 + Elo difference against R1
IMS is a difference against a frozen reference configuration, not a rating from a ranking list.
The zero point is calibrated to the setting of this configuration, not to a public pool; comparisons with public ranking lists are therefore not permitted.
The reference configuration plays throttled and non-deterministically, so a repetition can easily deviate.
Measurement plot
Today this is one measurement with its error band, not a trend; the curve appears only as further builds are measured.
Measurements
Measurements and conditions — project measurement, not in the register
| Build | Date | IMS | Half-width | Games | W/D/L | Pentanomial | Reference |
|---|---|---|---|---|---|---|---|
| 0.1.58 | 2026-09-06 | 2363 | ±26 (nominal 95%) | 800 (fixed game count, no SPRT Sequential probability ratio test. Games are played until the accumulated evidence reaches one of two bounds; then the test stops.) | 558 / 34 / 208 | 28 / 7 / 145 / 27 / 193 | R1 |
W/D/L: wins / draws / losses; pentanomial Games are played in pairs with swapped colours; the five counts are the pairs scoring 0, ½, 1, 1½ and 2 points.: game pairs scoring 0 / ½ / 1 / 1½ / 2 points; conditions per reference: see Reference configuration.
Reference configuration
Frozen reference R1
| Property | Value |
|---|---|
| Engine | Stockfish 19 |
| Build | sf_19, Linux x86-64 universal |
| Options | UCI_LimitStrength=true UCI_Elo=2200 |
| IMS | 2200 |
| Time control | 10+0.1 |
| Book | 8moves_v3 · 34,700 positions |
| Hash (MB) | 64 |
| Threads | 1 |
| Adjudication | none |
| Frozen | 2026-09-05 |
The reference configuration plays with limited strength and is not deterministic; a repeat measurement may differ slightly.
The authors of the engine used as the reference did not know of this measurement, took no part in it, and did not consent to it. The program was used solely as freely available software under its licence.