---
title: "mlab-ext-boost-metric — Mova code model"
description: "Mova code model of mlab/tests/ext_boost.rs: components with their labels, obernants and the model text."
url: "https://groupants.elamur.ai/free/en/mova/mlab/tests/ext_boost.rs.groupant/metric.groupant/"
---
Elamur: [Mova](https://md.mova.elamur.ai/free/en/) · [Dictionary](https://md.dictionary.elamur.ai/free/en/) · [Research](https://md.research.elamur.ai/free/en/) · **Groupants**

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# mlab-ext-boost-metric

The groupant beside mlab/tests/ext_boost.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:** [`mlab/tests/ext_boost.rs`](https://github.com/ElamurAI/mova-free/blob/main/mlab/tests/ext_boost.rs)
- **source SHA-256:** `7fa4b847808f0a48…`
- **covers:** measure retains normal reference values only; e=abs((got-want)/want)/EPSILON with NaN got=>infinity, strict greater updates first worst. Existing CASES bound4eps; synthetic tests do not certify those datasets. (bytes 2204–4687)
- **part of:** [mlab-ext-boost](https://md.groupants.elamur.ai/free/en/mova/mlab/tests/ext_boost.rs.groupant/)
- **repository folder:** [`mlab/tests/ext_boost.rs.groupant/metric.groupant`](https://github.com/ElamurAI/mova-free/tree/main/mlab/tests/ext_boost.rs.groupant/metric.groupant)
- **repository commit:** `48f2e6f74146`

> **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 | [approximant](#approximant) |
| **ast** | partial | `../syntax.json` |
| **cost** | symbolic source derived | [invariant](#invariant) |
| **descriptant** | present | [descriptant](#descriptant) |
| **invariant** | partial | [invariant](#invariant) |
| **tests** | partial bounded parent evidence | [tests](#tests) |

## 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 |
|---|---|---|---|
| `behavior_complement` | behavior_complement | partial source derived model | [behavior_complement](#behavior-complement) |
| `reverse_reconstruction` | reverse_reconstruction | partial source derived model | [reverse_reconstruction](#reverse-reconstruction) |
| `zero_metric` | zero_metric | partial source derived model | [zero_metric](#zero-metric) |
| `fault_witness` | fault_witness | partial source derived model | [fault_witness](#fault-witness) |
| `branch_relation` | branch_relation | partial source derived model | [branch_relation](#branch-relation) |
| `resource_cost` | resource_cost | partial source derived model | [resource_cost](#resource-cost) |

## Model text


### descriptant

#### mlab-ext-boost-metric

measure retains normal reference values only; e=abs((got-want)/want)/EPSILON with NaN got=>infinity, strict greater updates first worst. Existing CASES bound4eps; synthetic tests do not certify those datasets.

Epoch 2026-10-31: isolated source-bound fragment over bytes [2204,4687); includes no claim beyond this relation. Source hash 7fa4b847808f0a485411988bb342bd0b0540d350c50e6166f08224c1dbac9dfc.

### approximant

#### metric: forward relation

measure retains normal reference values only; e=abs((got-want)/want)/EPSILON with NaN got=>infinity, strict greater updates first worst. Existing CASES bound4eps; synthetic tests do not certify those datasets.

Domain: Synthetic bounded rectangular rows with valid col index; dataset suites deliberately not executed.

Executable surrogate gap: no measured cheaper implementation with a useful scoped metric is supplied. Categorical/error/effect relations are exact obligations, not percent losses. Future numeric caps only1/2/5/10%.

### invariant

#### metric: invariant and cost

Relative metric is undefined at0 and deliberately excluded; this is not a zero-reference accuracy claim.

erf fault adds1 to first output; synthetic erf0 confirms hook, without running frozen Boost points.

Scope-specific cost: O(rows) filtering and discrepancy scan plus interpreter vector execution; O(rows) references/results, zero references removed before call.

### models

### behavior_complement

Zero/subnormal/NaN/infinite reference values do not contribute. max_eps0 leaves worst_xNaN; ties do not update worst.

### reverse_reconstruction

Stat admits all row sets with same normal count and maximum relative discrepancy, including arbitrary excluded rows; worst_x alone not full error curve.

### zero_metric

Relative metric is undefined at0 and deliberately excluded; this is not a zero-reference accuracy claim.

### fault_witness

erf fault adds1 to first output; synthetic erf0 confirms hook, without running frozen Boost points.

### branch_relation

measure retains normal reference values only; e=abs((got-want)/want)/EPSILON with NaN got=>infinity, strict greater updates first worst. Existing CASES bound4eps; synthetic tests do not certify those datasets.

### resource_cost

O(rows) filtering and discrepancy scan plus interpreter vector execution; O(rows) references/results, zero references removed before call.

### tests

#### Evidence boundary

See ../tests.md for the actual selected source test and mutant. These tests sample the file, not every fragment branch. Zero/subnormal/NaN/infinite reference values do not contribute. max_eps0 leaves worst_xNaN; ties do not update worst. Other branches here are source-derived and unexecuted unless the parent test explicitly calls them.