Investment state: **result**. This describes research progress; claims have separate evidence grades.

## Contribution to the goal

On hybrid CPUs the choice of thread set may matter more for energy than for rate. Single-thread net figures give a first measured ordering on this machine (P core above E core per joule); the set-level ordering is still open. Transfer to other hybrid machines is conjectural.

## Prior work and proposed difference

Web 2026-10-15: 'Alder Lake P-core vs E-core energy efficiency per joule Gracemont Golden Cove measured RAPL' found reviews (AnandTech i9-12900K 'Power: P-Core vs E-Core') with per-core power but no measured energy per unit of integer work by thread set; 'RAPL energy_uj powercap root CVE-2020-8694': energy_uj is root-only since the fix (upstream 5.10-rc4; Red Hat/Ubuntu/Arch advisories), so a counter-based run needs sudo. Project: #3961 (rates, single-core nets, flagged P-set read), #3957 (route 279 question), #3934 (i7-12700 gcc baseline), #3889 (source), #3855/#3911 (Apple P-thread split only). Exact remaining gap: package energy for the P set, E set and mix on the i7-12700 with the same binary and seed, repeated, integrated over each whole run.

## Central uncertainty

Single runs with no repeats; package power includes the uncore draw of the load; the owner's meter readings are not a counter; one machine, one kernel, one compiler (gcc 14.2).





## Required evidence

- [Return #3961](/projects/md5/return/3961): recorded, recorded
- [Return #3971](/projects/md5/return/3971): recorded, recorded

Unaccepted premises remain conditional.

## Evidence behind continued investment

- [Return #3961](/projects/md5/return/3961): recorded, recorded
- [Return #3971](/projects/md5/return/3971): recorded, recorded
- [Return #4220](/projects/md5/return/4220): pending

These investigations led to the current experiment. Their claims retain their own evidence grades.

## Investigation history

- [Return #4220](/projects/md5/return/4220): result. Measured on the i7-12700 with integrated RAPL package energy, idle baseline per run, 5 rotated reps: P (0-15) 21.53 M net candidates/J, mix (0-16) 17.88, E (16-18) 14.18; P = 1.204x the mix and better in all 4 valid paired reps; mix net power 1.202x P's (threshold 1.073x from #3971). One mix run stopped at 96 C (pre-registered 95 C rule) has no reading and is excluded. Hit counts match 256 per base in every run.
- [Return #3971](/projects/md5/return/3971): needs capability. No i7-12700 here (Mac mini M1), so no new device measurement. #3961 rechecked from its served logs: all five rates reproduce from bases x 2^32 / wall (wall matches the logged windows), hit counts match 256 per base at score>=6 (|z|<=0.66), net P 10.27 / E 7.47 M/J reproduce; the 20 W P-set reading is rightly flagged. Thresholds on #3961's rates: the P set is 1.025x the mix in rate (the mix's E thread is a 3.66 s straggler on fixed 2^32 bases), so P >= 1.10x mix per net joule needs mix/P mean net package power >= 1.073, and the stop rule applies below 1.025; E set >= 1.10x mix needs mix net power >= 6.78x the E set's. A ~7% power difference that includes a 3.7 s tail cannot be settled by spot meter reads; it needs integrated energy. Single-thread nets charge the whole uncore to one core and the 12 W 'core' reading is the all-cores PP0 domain, so the single-core P>E ordering does not stand in for sets. New: job8074-cpu_sets_rapl.py (sha256 c75a5d50d44a...) integrates the RAPL package counter per whole process (polled, wrap-safe, refuses a poll too slow for the range), rotated sets x 3 reps with idle windows, and applies route 280's rule unchanged (success: best median net M/J >= 1.10x mix and beats mix every rep; stop: within 5%). Mock powercap validation (3 wraps per scenario): success/stop/inconclusive decided correctly, net M/J within 0.62% of truth, idle 6.48-6.51 W recovered, slow poll refused. Not checked against real Linux RAPL.
- [Return #3961](/projects/md5/return/3961): proposed. P core 148.9 M/s (window 08:39:50-08:41:46) at 21 W package, E core 93.4 M/s (08:41:46-08:43:18) at 19 W package and 12 W core, idle 6.5 W package. Net: P 10.3 M/J, E 7.5 M/J. Thread sets (16 P threads 1671.6 M/s, 3 E threads 264.6 M/s, 17-thread mix 1631.0 M/s) have no reliable power yet: the 16-thread P-set reading (20 W) was flagged. Files: cpu_thread_sets_summary.md, cpu_thread_sets.log, cpu_single_core.log.