Elamur Groupantsworld-ans-metric-lcs-row
The groupant beside world/src/ans.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial source model | forward |
| ast | partial | ../../syntax.json |
| composition | partial source model | parent-interaction |
| cost | partial source model | cost |
| descriptant | partial source model | epoch-memory |
| invariant | partial source model | invariant |
| tests | partial source model | checks |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
world-ans-metric-lcs-row-behavior-complement | behavior_complement | partial source model | behavior-complement |
world-ans-metric-lcs-row-reverse-reconstruction | reverse_reconstruction | partial source model | reverse-reconstruction |
world-ans-metric-lcs-row-parent-interaction | composition_relation | partial source model | parent-interaction |
world-ans-metric-lcs-row-boundary | constraint_relation | partial source model | boundary |
world-ans-metric-lcs-row-information | information_projection | partial source model | information |
world-ans-metric-lcs-row-cost | resource_relation | partial source model | cost |
Model text
Wave34, 2026-10-31. Subject: world-ans-metric-lcs-row, current source SHA d8d94c891e347d2b640744b20c4662dc35064368e7d4d9253c4954b4297e1e09. Domain: one terminating supplied-input helper transition; valid indices, sufficient memory and finite strings/trees/worlds. Source-derived partial relations, not a verified universal theorem. All views below share this domain and exact manifest scope; specialized assumptions are stated locally. No executable percentage approximant is claimed.
forward
For each a token keep saved previous-row diagonal; for each b token set cell to diagonal+1 on equality, else max(previous-row same column, current-row left). Return final cell.
invariant
Returned length cannot exceed min(n,m); unequal singleton streams cannot return 1. Reordering tokens is not generally score-preserving.
behavior-complement
Returned length cannot exceed min(n,m); unequal singleton streams cannot return 1. Reordering tokens is not generally score-preserving.
reverse-reconstruction
A length k admits every sequence pair with longest common subsequence k; many matching witnesses and token spellings may realize it. k=0 contains disjoint alphabets and either empty sequence, without unique reconstruction.
parent-interaction
rouge_l tokenizes first, bypasses empty streams, then consumes LCS for harmonic precision/recall; rouge_q takes best nonblank reference. DP length does not establish semantic answer quality.
boundary
After column j, dp[j+1] is current-prefix optimum while prev is the previous-row diagonal for the next cell; overwriting prev too early destroys dependencies.
information
Symmetry holds for returned length though space cost depends on the second input. Repeated equal tokens need distinct subsequence positions.
cost
Exactly nm inner iterations, m+1 usize cells, O(nm) time and O(m) auxiliary memory excluding token input; no task-error surrogate.
checks
Existing independent subset enumeration over 961 binary sequence pairs; finite test is not general correctness proof.
Exact selected native boundary: cargo test --offline --locked -p world --lib ans::wave8_models::lcs_matches_subsequence_oracle -- --exact --test-threads=1. Repeated in debug and release; see the current file-level wave34 evidence and external native-receipts.json.
assurance
The behavior-complement is an inner exclusion hypothesis over admissible input/output pairs, derived from branch order; not the complement of an incomplete model of the entire file. Reverse reconstruction is the compatible antecedent relation, retaining every modeled ambiguity rather than a chosen inverse. Parent-interaction is a composition relation, boundary a constraint relation, information an information/state projection, and cost a resource relation. The named checks are finite falsifiers; unexecuted branches remain source-inspected gaps. No parser/model/teacher/corpus/frozen assessment was run.
epoch-memory
New child in wave34; no prior child renamed or counted. Parent historical wave8/wave9 evidence remains historical. Current raw receipts are in the external wave34 reasoning run; source syntax is partial, macros opaque, and no semantic AST or general proof is supplied.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/world/src/ans.rs.groupant/metric.groupant/lcs-row.groupant/