📐algorithm-smawk

The groupant beside algorithms/src/smawk/mod.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

Components

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.

Model text

descriptant

smawk mod.rs

Original std-only implementation and independent fixtures. Aggarwal, Klawe, Moran, Shor and Wilber (1987), Geometric applications of a matrix-searching algorithm.

Prospective model saved before changes in $MOVA_DATA/runs/octopus-wave20-dp-2026-10-30/prospective.md. Current epoch 2026-10-30: exact optimization with explicit bounded-resource outcomes. Finite oracle agreement does not establish the caller's monotonicity premises. No timing or whole-Mova speed claim.

approximant

Forward model

Reduce columns using a stack; strict improvements pop while ties retain earlier columns. Recursively solve odd rows, then interpolate even rows between adjacent odd minima. Pure deterministic matrix callback; every submatrix has nondecreasing leftmost row minima (total monotonicity), not checked.

Cost

O(rows+cols) callback evaluations and O(rows+cols) live storage; callback cost excluded. Each attempted callback checks max_evaluations first. Allocations use try_reserve_exact; recursive row count halves. Empty rows return before column validation, then EmptyColumns, byte dimensions, allocation, evaluation budget.

Invariants and limits

Owned input slices remain unchanged. Deterministic ties and traversal; callback panics propagate and purity/monotonicity remain caller obligations. No allocator-refusal injection, no semantic AST proof, no universal finite-test proof. Checked arithmetic reports errors rather than wrapping.

Executable approximant gap

No executable surrogate is attached: categorical reachability/argmin has no justified relaxed metric here. Objective-only surrogate speed/error has not been measured. Existing knapsack surrogate is not automatically transferable. No 1/2/5/10% profile or approximate substitution is claimed.

models

behavior_complement

For constant matrix, every nonzero returned column is excluded by left tie policy. Under total monotonicity a returned row column excludes any lower-valued column or earlier equal column.

reverse_reconstruction

Minima vector [0,0] admits every constant 2-by-c matrix and rows [0,1,...]. Off-minimum values are not recovered; lawful matrices sharing leftmost minima form the preimage.

row_translation

Adding an exact representable constant to each row preserves its comparisons, total monotonicity and minima.

positive_scale

Positive exact representable integer scaling of all callback values preserves strict/equal comparisons and result.

restriction

Restricting to ordered row and column subsets preserves total monotonicity, but minima must be recomputed among surviving columns.

budget_prefix

An evaluation cap b invokes the callback at most b times; cap failure contains no output vector. Repeated calls to the same entry still count.

tests

Checks

cargo test -p mova-algorithms smawk::tests

Independent small oracle and resource boundary fixtures live in ../tests.rs. Repeated debug/release and compiled mutation receipts: $MOVA_DATA/runs/octopus-wave20-dp-2026-10-30.

combiner

Composition

Raw mod.rs syntax and mathematical recurrence are separate evidence. The partial syntax projection binds the exact source bytes but does not certify the recurrence. Oracle tests compare observable outputs; typed relations constrain lawful transformations and compatible preimages. For smawk, resource caps and checked failures remain separate from mathematical objective equivalence. Prospective expectations remain unchanged; finite validation cannot turn monotonicity assumptions into runtime validation.

validation

Validation — 2026-10-30

Ten new native tests cover five exact kernels. Full mova-algorithms library: 557 tests pass in two debug and two release executions; sorted native test outcomes agree byte-for-byte across all four. Strict all-target Clippy and focused rustfmt pass. External receipts: $MOVA_DATA/runs/octopus-wave20-dp-2026-10-30/{debug1,debug2,release1,release2,clippy}.log.

Compiled production controls: zero initial subset bit, forced zero MITM objective, right-tie SMAWK reduction, forced zero layered-DP objective and forced zero BST objective all fail named equality assertions. Byte restoration followed by full positive library rerun passes. A separate SMAWK interpolation tie mutation fails lawful_matrices after adding half-integer squared-distance centers; the restored focused test passes. Receipts: controls.log, mutant-*.log, restored.log, smawk-restored.log in the same external run directory. The original constant-matrix fixture alone did not distinguish interpolation ties; the stronger fixture closes that observed gap.

Every source/test file has two independently generated identical syntax projections and current source SHA. An isolated ten-leaf modelcheck groupants run reports valid=true, diagnostics=[], ten sidecars, zero missing source sidecars; the temporary collection parent has no sidecar and makes no composition claim. Root integration owns global registry and ancestor binding checks.

No timing speedup, machine-independent resource guarantee, allocation-failure injection, monotonicity validation, or end-to-end Mova improvement is inferred. Successful finite tests certify the listed observations only. No teacher, model, corpus or live database operations were used.

This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/algorithms/src/smawk/mod.rs.groupant/