Sylpheed/docs/re/mission-liveness-probe.md

A motion-independent live roster — and what n probably is

Status: ✅ the enumeration method; ✅ the hunting pilot gets kills; 🔴 "no births" cannot distinguish the wave models; 🟡 the member field n looks like a craft count, with a confound that must be removed before believing it.

✅ Enumerate by definition pointer, not by motion

entities2.moving() finds entities by displacement between two samples, so anything stationary in the window is invisible. That is the whole explanation for the ±10 swing that made the previous run's entity count useless (mission-wave-arrivals.md).

tools/re-capture/liveness_probe.py scans the entity heap (0xBD000000–0xBE000000) for aligned words equal to a known unit-definition VA instead. Moving or not, an entity is counted. Hull is f32 at position + 0x154 (HULL_OFF, already confirmed in pilot.py), so a death is a hull crossing to ≤ 0.

The difference is immediate — the series is monotone instead of oscillating:

t= 15s  294 alive   born 0  died 0  gone 4
t= 36s  290         born 0  died 0  gone 4
t= 57s  289         born 0  died 1  gone 0   <- e010_ADAN_Attacker_S
t= 78s  286         born 0  died 0  gone 4
t=100s  286         born 0  died 0  gone 0
t=143s  282         born 0  died 0  gone 4
t=164s  280         born 0  died 0  gone 2

Total decline 298 → 280 = 18, matching the 18 "gone" events exactly.

✅ The hunting pilot kills

One hull crossing was caught directly — an e010_ADAN_Attacker_S at t = 57 s — plus 18 disappearances. The previous run's worry that SYLPH_HUNT shoots but never destroys anything is settled: it does.

🔴 "No births" does not separate the two wave models

Zero entities appeared in 164 s. That looks like evidence against clock-driven arrivals at t = 90/120 s — and it is not, because the roster finding already established that all of a mission's entities are allocated at load. If every participant exists from the first frame, then neither model produces a "birth", and the observation is consistent with both. Recorded so the next run does not mistake it for a result: an arrival must be a state change on an existing entity, not an allocation.

🟡 n looks like the number of craft per roster member

The member tuple's third field n has been ❔ since the roster was decoded. Comparing the static sum(n) per unit type against what is resident:

unit	members	sum(n)	sites found
UN_e007_ADAN_Turret	21	216	214
UN_e105_ADAN_Cruiser	7	7	6
UN_e106_ADAN_Destroyer	19	19	14
UN_f105_TCAF_Cruiser	11	11	4
UN_f106_TCAF_Destroyer	14	16	10
UN_e010_ADAN_Attacker_S	9	45	32
UN_f001_TCAF_DeltaSaber_T	7	7	14
UN_f001_..._Player	1	1	2

The turret row is striking: 216 predicted against 214 found, with the count already falling before the first sample. Count alone predicts 21, which is off by an order of magnitude. So n scaling a member into a flight of craft fits the dominant unit type well.

It is not promoted, because the measurement has an unquantified confound. The player is one member and yields two sites, and DeltaSaber_T yields exactly double its sum(n) — so at least some entity types hold more than one pointer to their definition. What the probe counts is definition-pointer sites, not entities, and until those are collapsed into distinct entities the turret match could be a coincidence between a ×1 multiplicity and a ×1 ratio. The capital-ship rows undershoot instead, which is separately explained by phases 2 and 3 not having started.

Next

Collapse sites into entities before re-testing n — cluster sites by their implied entity base and take distinct bases. Then the table above becomes a real test rather than a suggestive one. The same de-duplication is a precondition for using this probe to watch an arrival, since an arrival is now known to be a state change rather than an allocation.

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Sites really are entities — and n does not survive the fix (2026-08-24)

✅ The multiplicity confound is refuted

The worry was that some entity types hold several pointers to their definition, so "sites" over-counted entities. Measured, it does not happen:

• Gaps between consecutive same-unit sites are all ≥ 0x1000, and 274 of them are exactly 0x1000. Entities are page-spaced; there are no pairs sitting a few bytes apart that a clustering pass could merge.
• Clustering at any threshold below 0x1000 therefore gives ratio 1.00 for every unit type — 298 sites, 298 entities.
• Hull is plausible (0 < h ≤ 200000) on 298 of 298 clustered bases at delta 0x130. These are real objects, not stray pointer words.

So the previous run's counts were right after all, and the reason the player shows two is that there genuinely are two such objects — not two pointers to one.

(The delta spectrum came back empty this run: entities2.moving() found no movers in its sample window, so find_delta had nothing to vote on. It does not affect the conclusion — every gap is ≥ 0x1000, so any threshold below that gives the same clustering — but the threshold was a fallback, not a measurement, and that is worth knowing if this probe is reused.)

🔴 With the confound gone, the n = craft-per-member reading fails

unit	members	sum(n)	formation slots	live entities
UN_e007_ADAN_Turret	21	216	630	214
UN_e010_ADAN_Attacker_S	9	45	126	32
UN_f001_TCAF_DeltaSaber_T	7	7	23	14
UN_e106_ADAN_Destroyer	19	19	23	14
UN_f106_TCAF_Destroyer	14	16	16	10
UN_e105_ADAN_Cruiser	7	7	7	6
UN_f105_TCAF_Cruiser	11	11	11	4
UN_f001_..._Player	1	1	3	2
UN_f101_TCAF_Acropolis	1	1	6	2

sum(n) fits the turret row well (216 against 214, with kills already recorded before the sample). It does not generalise: DeltaSaber_T, Player and Acropolis all come out at exactly twice their sum(n), and an undershoot can be blamed on phases 2–3 not having started but an overshoot cannot.

Two different multipliers are at work and only one of them is explained. n goes back to ❔ — the 🟡 in the previous section is withdrawn. What the turret row shows is only that a roster member expands into many craft; it does not show that n is the expansion factor.

🔴 Formation slot count is not the expansion factor either

Tested because the formation names carry a size suffix. FormationSet_S02.tbl gives 630 turret slots against 214 live — an overshoot of 3×. Rejected.

✅ Side result: FormationSet FrameCount is the slot count

The frame count of a formation record is the number of slots, and the name suffix usually agrees: Formation_ADAN_Turret07_30 → 30, Formation_TCAF_ArrowHead03_64 → 64, Formation_4_Bird → 4. One exception found: Formation_ADAN_AttackerS03_12 has 14 slots, not 12, so the suffix is a label rather than a guarantee.

Also worth recording

The live entity population (298) is not the 116 0x820af030 roster records. Both structures exist simultaneously: 116 records, one per UnitGroup member, and 298 heap objects, one per actual craft. Whatever maps one onto the other is the expansion rule, and it is still unknown.