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

The groupant beside gparse/src/eisner.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:** [`gparse/src/eisner.rs`](https://github.com/ElamurAI/mova-free/blob/main/gparse/src/eisner.rs)
- **source SHA-256:** `10e4a00f4c14c913…`
- **covers:** Stack expands complete to incomplete spans and writes one parent for each dependent then strips root slot. (bytes 2300–3181)
- **part of:** [gparse-eisner](https://md.groupants.elamur.ai/free/en/mova/gparse/src/eisner.rs.groupant/)
- **repository folder:** [`gparse/src/eisner.rs.groupant/backtrace.groupant`](https://github.com/ElamurAI/mova-free/tree/main/gparse/src/eisner.rs.groupant/backtrace.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 checks | [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) |
| `complete_split` | complete_split | partial source derived model | [complete_split](#complete-split) |
| `edge_write` | edge_write | partial source derived model | [edge_write](#edge-write) |
| `termination_domain` | termination_domain | partial source derived model | [termination_domain](#termination-domain) |
| `root_projection` | root_projection | partial source derived model | [root_projection](#root-projection) |

## Model text


### descriptant

#### Source-bound description

Stack expands complete to incomplete spans and writes one parent for each dependent then strips root slot.

##### Epoch 2026-10-31

Prospective model was recorded before edits. Added tests use bounded synthetic fixtures; production algorithms unchanged. Coverage is partial, not proof. No trained corpus, live teacher or throughput experiment was executed.

### approximant

#### Forward approximant

Stack expands complete to incomplete spans and writes one parent for each dependent then strips root slot.

Domain: valid source-specific dimensions and resources stated in invariant; no automatic production substitution. Numerical observations are finite checks, not an end-to-end relative bound. Executable Rust surrogate: unsupported gap; existing exact tests are not surrogates. Future metric-specific caps may be 1/2/5/10%, never above 10%.

### invariant

#### Invariant and cost

s==t stops expansion; stack uses backpointer arrays from DP.

##### Cost

O(n) backtrace events/output after charts, O(n) explicit stack.

Allocation, finite arithmetic, platform dimensions and external failures are not universally certified.

### models

## Typed model catalog

### behavior_complement

Backtrace never reads sc directly; its behavior is determined by chosen root and stored backpointers.

### reverse_reconstruction

Heads alone cannot reconstruct scores or unused split choices.

### complete_split

Complete-left pushes complete(s,r) and incomplete(r,t); complete-right pushes incomplete(s,r) and complete(r,t).

### edge_write

Incomplete-left writes heads[s]=t, right writes heads[t]=s.

### termination_domain

With valid chart splits produced by finite intermediate candidates, span sizes decrease until s==t. Nonfinite recurrences are outside this guarantee.

### root_projection

heads[0] omitted from returned heads[1..]; heads[root]=0.

### tests

#### Checks and limits

Selected parent checks relevant to this fragment (not exhaustive): eisner::tests::best_tree_with_one_root; eisner::wave30::empty_singleton_and_first_root_tie; decoder_accepts_no_words

Selected commands run twice debug and twice release; exact receipts and source-to-test mapping retained in wave30 gparse external run directory. Tests do not certify allocation failure, all NaN/overflow inputs, trained-model accuracy or corpus timing. Compiled mutants cover selected boundaries; per-source coverage is recorded in the external map, not presumed.