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feat(logspace): clock actual fair-coin configuration matrices - #1778

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SamuelSchlesinger merged 3 commits into
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feat/logspace-time-layer
Oct 30, 2026
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SamuelSchlesinger merged 3 commits into
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feat/logspace-time-layer

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@SamuelSchlesinger

@SamuelSchlesinger SamuelSchlesinger commented Oct 30, 2026 •

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Why

The finite-time BPL reduction needs a strictly forward system whose value is the actual machine's acceptance probability. An absorbing configuration matrix alone is not strictly forward, and paying accepting rewards before the terminal clock would count accepting runs repeatedly.

Changes

  • Construct Matrix.timeLayer T S on clocked vertices, with edges only to the next clock and rewards only at the final clock. Prove strict upper triangularity, the exact vertex count, nonnegativity, substochasticity, and bounded remaining-horizon potentials.
  • Prove the linear-system equation, determinant one, and inverse formula for the actual remaining-power solution.
  • Specialize to half the ordinary absorbing fair-coin configuration matrix. The initial potential equals the finite-time acceptance count divided by 2^T, and agrees with the live matrix's first-stop sum.
  • Instantiate an actual BPL witness, preserving its 2/3-versus-1/3 acceptance gap with at most (T + 1) * T clocked vertices.
  • Connect individual clocked entries to feat(logspace): certify local fair-coin configuration counts #1763's compact-ID count reader under its explicit fit, symbol, and reachable-space premises.

Stack and scope

Builds on merged #1763 (actual parent 7e32b150). Progress toward #1444. The native bounded enumeration, whole-input symbol-query composition, incoming paired ports, and deterministic estimator with its space proof remain open. The finite vertex set and within-layer order are chosen input by input; no native enumeration algorithm is certified. This PR proves a semantic reduction and a local entry-reader bridge; it does not prove BPL ⊆ L or the full L = RL = BPL = coRL chain.

Validation and independent review

  • Both library modules and all 185 lines of focused tests compile with the pinned toolchain, project options, and -DwarningAsError=true.
  • Tests use an actual looping fair-coin machine: its acceptance probability after two steps is 3/4, and a reachable compact-reader edge has weight 1/2. Additional cases cover zero horizons, terminal-only rewards, absorbing transitions, strict forwardness, and bounded potentials.
  • Tracked aggregate registration, committed-import verification, focused hygiene, and whitespace checks pass.
  • Independent non-author review by lean_environment approved exact source commit dafd85f98e5fd78eec31900dff411b0c5bf8c138 without findings. The integrated source and tests match that reviewed snapshot.
  • The reviewed source passed original CI 41102175480. The current ordinary main/aggregate restack preserves all three source/test payloads byte for byte and passes focused checks plus all six default gates locally. Current validation and integration evidence tracks fresh hosted CI before queueing.

AI assistance: ChatGPT authored and integrated these proofs, with separate non-author agent review. This semantic construction is independent of the moment exponent.

Read each fixed-coin edge of the compact configuration graph and add the
two contributions, preserving multiplicity when the successors coincide.
Certify the count and live-count routines with the existing native space
combinators. Prove normalized tape and canonical-view ID injectivity, then
identify the queries with actual configMatrix/liveConfigMatrix entries.
Reachable-logspace corollaries derive the representation conditions from
RunsInSpace at the prescribed polynomial radix.

Tests use actual zero-tape machines and reachable views to distinguish
zero, one and two coin branches, absorbing and zero-live halted rows,
invalid IDs, and the exact binary argument space certificate.

Validation on base df2279f plus this four-file diff: all three modules and
the test pass direct Lean 4.36.0-rc2 checks with warningAsError=true and
repository linter options, with no diagnostics. Focused hygiene
--check-simp and staged git diff --check pass. Outputs are isolated and
shared compiled dependencies are read-only. Aggregate wiring, independent
review and the full CI gates are left to the coordinating integration.

This is local matrix access, not bounded vertex enumeration, time layering,
an estimator implementation or the BPL subset L endpoint. No selected
abstract or catalogue impact. AI assistance: ChatGPT (GPT-6 Astra), worker
codex-logspace-coin-multiplicity-20261030, wrote and validated these files.

Independent non-author source/API review by compression_review approved exact source revision be84b9de9d7de13f0d99a3ceb54649ef57f9f7d2, including native resource certificates and exact configuration-matrix bridges, with no findings. Reviewed source files are unchanged after integration onto updated main.
Integrated strict source/test builds, tracked aggregate check, whitespace and committed import checks pass. Full integration gates run in PR CI.
Construct a time-layered matrix with edges only to the next clock layer,
terminal-only reward, and the explicit remaining-horizon potential. Prove
strict upper triangularity, substochasticity, bounds on every potential
coordinate, the linear-system identity, determinant one, and its inverse
solution. This follows the ordinary absorbing-matrix convention of the
pinned model.tex Lemma 2.1 (OpenAI2026LogSpace, revision 7ef5c0cc).

Specialize to the actual half-normalized fair-coin configuration matrix
and prove its clock-zero potential is the native finite-time acceptance
frequency and the existing finite sum of first-stop live terms. Identify
clocked entries with the certified compact-ID coin-count reader. Apply the
existing BPL configuration-matrix theorem to obtain concrete polynomial-size
strict-forward systems with bounded potential and the 2/3 versus 1/3 gap.

Tests realize a zero-work-tape machine that loops on false and accepts on
true. They prove its actual two-step acceptance probability is 3/4 and
read a nonzero clocked edge from the compact IDs. Additional checks cover
an absorbing matrix, terminal-only reward, zero horizon, the explicit
linear system and inverse, and the exact clocked cardinality.

Validation on base 406a68d plus this three-file diff: both library modules
and ComplexityTests/TimeLayer.lean pass direct Lean 4.36.0-rc2 with
warningAsError=true and repository linter options, without diagnostics.
Focused check_hygiene.py --check-simp and staged git diff --check pass.
Builds use only tiny isolated outputs and read-only compiled dependencies;
there are no Lake/cache/bootstrap operations. Aggregate registration and
full CI gates remain for coordinating integration. The final independent
review is pending; the two unchanged library snapshots already received
a no-findings source review from lean_environment.

This is a concrete semantic reduction. Bounded vertex enumeration,
composition with whole-input symbol access, incoming paired ports, the
recursive estimator, and the native BPL subset L endpoint remain open.
No selected abstract or catalogue impact. AI assistance: ChatGPT
(GPT-6 Astra), worker codex-time-layer-20261030, wrote and validated the
three files.

Independent non-author review by lean_environment approved exact source commit dafd85f98e5fd78eec31900dff411b0c5bf8c138 with no findings; integrated library and test bytes match that snapshot.
Integrated strict source/test builds, tracked aggregate check, whitespace and committed import checks pass. Full integration gates run in PR CI.

@edemaine edemaine left a comment

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Agent review by reviewer-codex-edemaine of 8e68800: approve. Read the complete layer over #1763 and reused its unchanged compact-reader coverage.

Clocked edges advance exactly one layer, including from absorbing halted views; terminal rows vanish and only terminal rewards are paid. The explicit remaining-power potential solves the system, is bounded at every view under the stated closedness/substochastic hypotheses, and its inverse follows from determinant one. The machine specialization preserves coin multiplicities and actual finite-time acceptance, agreeing with the first-stop live sum. The BPL corollary retains the rational 2/3–1/3 gap and (T+1)T size bound with machine/exponent chosen before inputs. Its ordering is explicitly nonconstructive. Local reader equality retains actual input-symbol, fit and canonical-output premises; the reachable version derives those from the existing space bound.

Checked the terminal-time mapping against pinned Lemma 2.1, pp.7–8. This is its semantic matrix component: bounded enumeration, whole-input composition, incoming paired ports and native estimation remain open. The actual looping-machine 3/4 probability, compact 1/2 edge, zero horizon and withheld-reward tests are meaningful. No findings or curated-abstract impact.

Aggregate and whitespace checks passed. Author reports strict focused source/tests; I ran no local Lean build. At inspection Lean CI 41102175480, title, Guide and Comparator were queued. This is agent review, not human approval.

SamuelSchlesinger commented Oct 30, 2026 •

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Non-author coordinator codex-faircoin-integrate-20261030-1651 — APPROVE source 3c7235c2d31c985ea5652c000022991f2e6b592a under the validated coordinator-fix rule, carrying forward the outside correctness/API review. The ordinary actual-main merge and canonical aggregate preserve all three reviewed source/test modes and blobs; no theorem, definition, proof or resource convention changed. Local all-six and focused checks passed, as did current Lean CI, Guide and Comparator.

Actually landed at 22:00:13 UTC as 8f4a49e47ddfa6eb1282205d4081f47949d65829, tree 94ee388b565e5869f597d723e1ad6cd11c25f1c6, exactly matching the neutral-text tail preflight. Git main and PR merge metadata agree; the three payloads remain identical and the aggregate is canonical. Merge-group CI passed all six strict gates at this exact checkout and uploaded artifact 13016031511 (metadata verified; no body downloaded). Exact-main CI also succeeded: its finalized log checks out 8f4a49e4, restores merge-group run 41131209958 attempt 1, reruns all six gates with zero Built Complexity lines, and publishes at 22:16:11 UTC. The public mapping returned HEAD/GET 200: 4,077 unique pairs, 183,478 bytes, SHA256 224d1f3cec561c22465839a90fcbc1130c98e08518213f6d705878ae9bea9a4e. All 51 new artifact references versus the saved, verified 9b511328 mapping returned HEAD 200; no artifact bodies were downloaded. Landing and usable-cache follow-through are complete.

The finite-time probability and terminal-only reward results retain their closure, native-ID, fit, canonical-state and supplied-symbol hypotheses. The BPL wrapper still chooses its finite configuration set/order separately for each input; uniform native enumeration, whole-input assembly, paired ports and the estimator remain open under #1444. This is not a BPL containment endpoint. Abstracts/rendering are unaffected; no new PDF review was needed. This is agent approval, not human approval.

Merge actual main af2d9bb into reviewed8e688004. Preserve the three reviewed library/test files byte-for-byte and retain every import in canonical order. This repairs only the actual-main/generated-aggregate integration delta; source proofs, statements, resource conventions and author credit are unchanged.
@SamuelSchlesinger
SamuelSchlesinger changed the base branch from feat/logspace-fair-coin-reader to main October 30, 2026 20:53
@SamuelSchlesinger
SamuelSchlesinger added this pull request to the merge queue Oct 30, 2026
Merged via the queue into main with commit 8f4a49e Oct 30, 2026
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