Elamur Groupantsgparse-test-softmax-backward
The groupant beside gparse/tests/softmax_backward.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 | approximant |
| ast | partial | syntax.json |
| composition | partial | composition |
| cost | symbolic source derived | invariant |
| descriptant | present | descriptant |
| evidence | executed finite checks | evidence |
| invariant | partial | invariant |
| tests | executed bounded checks | 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 |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
numerical_metric | numerical_metric | partial source derived model | numerical_metric |
effect_boundary | effect_boundary | partial source derived model | effect_boundary |
assurance_scope | assurance_scope | partial source derived model | assurance_scope |
failure_precedence | failure_precedence | partial source derived model | failure_precedence |
Parts
Model text
descriptant
Source-bound description
CUDA checks deterministic values/weights at widths 1,3,17,33,257, compares fused/reference forward and weighted VJP<2e-6 abs; independent f64 central differences at four coordinates each width use epsilon1e-4 and tolerance2e-6. Offset slices and transposes checked, large Ā±1000 rows remain finite and -1e9 columns zero; upstream fusion is no-gradient control. CPU F64 equality checks fallback.
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
CUDA checks deterministic values/weights at widths 1,3,17,33,257, compares fused/reference forward and weighted VJP<2e-6 abs; independent f64 central differences at four coordinates each width use epsilon1e-4 and tolerance2e-6. Offset slices and transposes checked, large Ā±1000 rows remain finite and -1e9 columns zero; upstream fusion is no-gradient control. CPU F64 equality checks fallback.
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
All thresholds are absolute finite-fixture measurements; no universal gradient error certificate. CPU dtype stays F64.
Cost
O(sum widths) tensor work and O(sum widths) for each selected finite-difference objective; tiny bounded GPU allocation.
Allocation, finite arithmetic, platform dimensions and external failures are not universally certified.
composition
Composition
CUDA checks deterministic values/weights at widths 1,3,17,33,257, compares fused/reference forward and weighted VJP<2e-6 abs; independent f64 central differences at four coordinates each width use epsilon1e-4 and tolerance2e-6. Offset slices and transposes checked, large Ā±1000 rows remain finite and -1e9 columns zero; upstream fusion is no-gradient control. CPU F64 equality checks fallback.
Scoped children
The byte-scoped children project distinct internal relations through the parent syntax file. The parent combines them in actual source order. Remaining declarations/tests outside child ranges belong to this parent. Their correctness does not establish external caller preconditions.
Interfaces and limits
All thresholds are absolute finite-fixture measurements; no universal gradient error certificate. CPU dtype stays F64.
A passing finite-difference inequality allows any derivative in the tolerance interval, not exact unique gradient; softmax input compatible logits differ by row shifts.
models
Typed model catalog
behavior_complement
Passing selected assertions excludes their stated counterexamples within the fixtures. No corpus/model-file mutation occurs in selected synthetic checks.
reverse_reconstruction
A passing finite-difference inequality allows any derivative in the tolerance interval, not exact unique gradient; softmax input compatible logits differ by row shifts.
numerical_metric
Mask zeros exact on two tested cells; forward and derivative comparisons use <2e-6 independently.
effect_boundary
Selected test process owns local fixture tensors/state; explicit CUDA tests serialize. No teacher/API, dataset or external model reads selected.
assurance_scope
Compiled selected assertions establish only finite observations; ignored experiments and backend allocation failures remain gaps.
failure_precedence
Fixture creation and backend operations must succeed before assertions; a compile-only result is distinct from executed assertions.
tests
Checks and limits
cpu_f64_uses_reference; fused_softmax_matches_reference_gradients_and_finite_differences
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.
See source execution evidence for exact names and unexecuted paths.
evidence
Execution evidence ā 2026-10-31
Source: gparse/tests/softmax_backward.rs
- cpu_f64_uses_reference: twice debug, twice release, all four exits 0.
- fused_softmax_matches_reference_gradients_and_finite_differences: twice debug, twice release, all four exits 0.
Controls
0 source-local compiled assertion mutants; 1 observed control tests including dependency mutations. Mutant compile exit0, assertion exit101, byte-exact restoration and positive rerun exit0. Per-source controls are listed in external source-test-map.json, not implied for every source.
Limits
Finite synthetic CPU/CUDA observations; no trained-corpus quality or all-input numeric guarantee.
CUDA softmax comparisons use absolute tolerance2e-6. GELU grid maxima observed: values0.0004734993, derivatives0.00086838007, finite difference0.0000005534244635896357; respective strict caps5e-4/1e-3/1e-5. These are finite observations, not percentage profiles or throughput claims.
Receipts: external wave30 gparse run native-commands.json, results.json, controls.json and source-test-map.json. Sorted exact test names/outcomes match per profile; numeric diagnostics and timings need not be byte-identical. Strict scoped library Clippy reports ten pre-existing production lints; appended test blocks were formatted independently without production reformatting.
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