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

The groupant beside world/src/schoolbench.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/schoolbench.rs`](https://github.com/ElamurAI/mova-free/blob/main/world/src/schoolbench.rs)
- **source SHA-256:** `31af0a29c60d6f58…`
- **covers:** Partition by stars, compute stable digest from seed/course/n, lexically sort digest-index pairs, take ceil(n_s/d), sort global indices. (bytes 1568–2423)
- **part of:** [world-schoolbench](https://md.groupants.elamur.ai/free/en/mova/world/src/schoolbench.rs.groupant/)
- **repository folder:** [`world/src/schoolbench.rs.groupant/selection.groupant`](https://github.com/ElamurAI/mova-free/tree/main/world/src/schoolbench.rs.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-schoolbench-selection-behavior-complement` | behavior_complement | partial source model | [behavior-complement](#behavior-complement) |
| `world-schoolbench-selection-reverse-reconstruction` | reverse_reconstruction | partial source model | [reverse-reconstruction](#reverse-reconstruction) |
| `world-schoolbench-selection-rank-oracle` | constraint_relation | partial source model | [rank-oracle](#rank-oracle) |
| `world-schoolbench-selection-nested-subsets` | order_relation | partial source model | [nested-subsets](#nested-subsets) |

## Model text


Source-bound epoch 2026-10-30. Every view below uses this exact source revision and finite inputs with sufficient allocation resources. Forward/absent/reverse relations observe only the stated projection; filesystem models assume fixed supplied dependencies and distinguish successful returns from partial effects. Status: partial source model, with bounded native evidence in evidence.md at the root sidecar. No approximation percentage, universal proof or school accuracy claim.

### forward
Partition by stars, compute stable digest from seed/course/n, lexically sort digest-index pairs, take ceil(n_s/d), sort global indices.

### invariant
Per nonempty stratum select at least one and at most n_s; Full selects every original index exactly once, even duplicate identities.

### cost
O(N identity bytes + sum n_s log n_s + K log K), O(N) stored pairs; hashes compared as strings.

### composition
Leaf projections share exact lesson identities, selected indices, text bytes and option ordering. Compose only with those shared values retained; isolated score/length observations cannot recover them. Source inspection identifies knowledge::main_args dispatch, schoolbench selected-lessons -> counts -> run_course_lessons -> trace scoring, and schooltools option_line -> canon -> tally/lint/edit. Tests execute native pure helpers and isolated snapshot/restore; no live course/parser/teacher call.

### epoch-memory
Initial coverage records tolerant parser/score semantics and per-file effect boundaries. Model review exposed the direct zero restore index panic, repaired after old-code failure. Benchmark score loop was extracted unchanged to a pure private helper to test actual classification and width/count gates. Lock constructor failure may leave a stale directory; argument failures can consume flags. These remain explicit source-inspected limitations.

### checks
Native module filters schoolbench:: and schooltools::, including eight new wave9 tests; independent finite rank/cadence/length/fraction oracles and a restore no-effect fixture. Raw evidence is external under $MOVA_DATA/runs/octopus-wave9-school-2026-10-30; root evidence.md binds outcomes. Macro bodies in syntax projection remain opaque; finite agreement does not certify unbounded input space.

### behavior-complement
Type: behavior_complement. Subject: world-schoolbench-selection, epoch 2026-10-30. Domain and observation: scoped inputs and projected outputs defined here. Operator/assumptions: For fixed inputs, inner absent results include reordered output, omissions in full, and selections violating per-stratum quota or rank. No assertion that different seeds necessarily yield different subsets.
Evidence/status: source-inspected relation with the bounded tests named under checks; unenumerated behavior remains unknown. Complement claims are inner constraints, reverse claims retain all compatible candidates rather than identifying a historical cause.

### reverse-reconstruction
Type: reverse_reconstruction. Subject: world-schoolbench-selection, epoch 2026-10-30. Domain and observation: scoped inputs and projected outputs defined here. Operator/assumptions: Selected indices constrain only quota and winning ranks. Any replacement lesson facts/questions with unchanged course/n/stars is compatible; rank ties preserve original indices. Hash preimage reconstruction is not implemented.
Evidence/status: source-inspected relation with the bounded tests named under checks; unenumerated behavior remains unknown. Complement claims are inner constraints, reverse claims retain all compatible candidates rather than identifying a historical cause.

### rank-oracle
Type: constraint_relation. Subject: world-schoolbench-selection, epoch 2026-10-30. Domain and observation: scoped inputs and projected outputs defined here. Operator/assumptions: Independent bounded oracle counts peers with smaller (digest,index) and includes i iff rank*d < stratum-size; 49 lengths times three seeds times three tiers =441 comparisons. It shares the digest primitive, so hash correctness is external.
Evidence/status: source-inspected relation with the bounded tests named under checks; unenumerated behavior remains unknown. Complement claims are inner constraints, reverse claims retain all compatible candidates rather than identifying a historical cause.

### nested-subsets
Type: order_relation. Subject: world-schoolbench-selection, epoch 2026-10-30. Domain and observation: scoped inputs and projected outputs defined here. Operator/assumptions: For same strata/ranks, ceil(n/8)<=ceil(n/3)<=n; prefixes compose into subset inclusion after chronological sorting. Changing lessons, stars or seed voids this premise.
Evidence/status: source-inspected relation with the bounded tests named under checks; unenumerated behavior remains unknown. Complement claims are inner constraints, reverse claims retain all compatible candidates rather than identifying a historical cause.