---
title: "world-school-student-state-selection — Mova code model"
description: "Mova code model of world/src/school.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/world/src/school.rs.groupant/student-state.groupant/selection.groupant/"
---
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# world-school-student-state-selection

The groupant beside world/src/school.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

- **kind:** groupant_fragment
- **status:** partial source bound model
- **source:** [`world/src/school.rs`](https://github.com/ElamurAI/mova-free/blob/main/world/src/school.rs)
- **source SHA-256:** `06aaec6f562c2acc…`
- **covers:** Choose T=acc when nonempty, else w. Sum T[f,o] over unique features in i128 and maximize (score,-op discriminant) over allowed; empty allowed defaults Add. Positive reasons for winner sort by decreasing weight then lexical key, truncated to three. Answer applies the chosen op. (bytes 19867–21049)
- **part of:** [world-school-student-state](https://md.groupants.elamur.ai/free/en/mova/world/src/school.rs.groupant/student-state.groupant/)
- **repository folder:** [`world/src/school.rs.groupant/student-state.groupant/selection.groupant`](https://github.com/ElamurAI/mova-free/tree/main/world/src/school.rs.groupant/student-state.groupant/selection.groupant)
- **repository commit:** `855da7bd4a7b`

> **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](#forward) |
| **ast** | partial | `../../syntax.json` |
| **composition** | partial source model | [composition](#composition) |
| **cost** | partial source model | [cost](#cost) |
| **descriptant** | partial source model | [epoch-memory](#epoch-memory) |
| **invariant** | partial source model | [invariant](#invariant) |
| **tests** | partial source model | [checks](#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-school-student-state-selection-behavior-complement` | behavior_complement | partial source model | [behavior-complement](#behavior-complement) |
| `world-school-student-state-selection-reverse-reconstruction` | reverse_reconstruction | partial source model | [reverse-reconstruction](#reverse-reconstruction) |
| `world-school-student-state-selection-coupling` | constraint_relation | partial source model | [coupling](#coupling) |
| `world-school-student-state-selection-observation-fiber` | information_loss | partial source model | [observation-fiber](#observation-fiber) |

## Model text


### forward

Choose T=acc when nonempty, else w. Sum T[f,o] over unique features in i128 and maximize (score,-op discriminant) over allowed; empty allowed defaults Add. Positive reasons for winner sort by decreasing weight then lexical key, truncated to three. Answer applies the chosen op.

### invariant

Tie order is Add<Sub<Mul<Div, regardless of allowed order. Why excludes nonpositive weights. On the supported 64-bit target at most usize::MAX i64 contributions fit in i128. p.op does not affect selection.

### cost

After feature generation O(F log K) scoring over constant four operations, O(F log F) reason sorting and O(F) storage. Scalar widening keeps this bound; constants unmeasured.

### composition

The same table feeds score and reasons. Tests compare MAX+MAX to MAX-1, reversed allowed order, empty allowed, and an unrelated accumulator activating the averaged table. No parser or teacher.

### epoch-memory

2026-10-30 initial school source-bound epoch. Prospective model: keep O(1) arithmetic/partition cost, widen aggregation scalars, and expose actual codecs without filesystem effects. Old native witnesses found unchecked operation, score, marginal vote, partition and duplicate-vote arithmetic; legacy serialization synthesized zero accumulators. Review found that dropping explicit zero accumulators also changed the prediction table. Both activation directions now have named tests. No speedup, approximate-error profile or general semantic proof is claimed. Unchecked update/world arithmetic retains representability premises.

### checks

cargo test -p world --lib school::wave12_models -- --test-threads=1. Root evidence.md binds exact source/evidence hashes, repeated debug/release outcomes and a compiled production mutation. Named fixture domains appear in composition. Syntax is a source-bound partial projection; macros remain opaque. No semantic AST or live school execution.

### behavior-complement

Subject/revision: manifest hash and byte scope. Universe: supplied finite inputs, fixed dependencies, successful allocation and the explicit arithmetic premises of this scope. Inner absent-behavior relation: A larger discriminant cannot win an equal-score tie against an allowed smaller one. Current weights cannot contribute while acc is nonempty. Negative/zero features cannot appear in why. These are source-derived constraints with finite named witnesses where indicated; external behavior remains unknown.

### reverse-reconstruction

Subject/revision: manifest hash. Operator: compatible preimage/converse, holding dependencies and admissibility fixed. For observed choice o retain all tables satisfying score(o)>=score(j), strictly greater where j has smaller discriminant. Observed reasons constrain positive entries and ordering but omitted entries leave many compatible tables. Partial relational description, not a complete inverse search or a unique causal history.

### coupling

Subject/revision: manifest hash. Constraint relation on stage identities and ordered intermediate states: The same table feeds score and reasons. Tests compare MAX+MAX to MAX-1, reversed allowed order, empty allowed, and an unrelated accumulator activating the averaged table. No parser or teacher. Supplied native joins and source inspection are distinct evidence.

### observation-fiber

Subject/revision: manifest hash. Domain: scoped inputs with the declared observation. The information-loss relation equates inputs whose observation agrees: Adding equal score offsets to all operations preserves the winner. Many tables share the top-three reasons; current weights alone cannot reveal accumulator activation. Finite tests do not establish unrestricted completeness.