Clean up unused public APIs

[GiggleLiu]

Summary

Audit identified ~50 unused or test-only public APIs across the codebase. These add maintenance burden, clutter documentation, and inflate the public API surface without providing value.

Tier 0: Completely Dead (0 uses anywhere) — Delete

Kind	Item	Location
fn	MappingResult::print_config()	src/rules/unitdiskmapping/ksg/mapping.rs:88
fn	MappingResult::print_config_flat()	src/rules/unitdiskmapping/ksg/mapping.rs:136
ctor	LinearConstraint::new()	src/models/optimization/ilp.rs:139 — shadowed by ::le/::ge/::eq (make pub(crate))
ctor	MaximumSetPacking::new()	src/models/set/maximum_set_packing.rs:63 — only ::with_weights is ever used
ctor	MinimumSetCovering::new()	src/models/set/minimum_set_covering.rs:70 — only ::with_weights is ever used
fn	apply_weighted_gadget_boxed_fn()	src/rules/unitdiskmapping/ksg/gadgets.rs:1647 — dead wrapper
fn	apply_triangular_simplifier_gadgets() + 4 try_apply_dangling_leg_* helpers	src/rules/unitdiskmapping/triangular/mod.rs:1221 — dead reimplementation
type	MatchedEntry	src/rules/graph.rs:1097 — pub struct in private scope, never named externally
type	LegacySourceCell	src/rules/unitdiskmapping/triangular/mod.rs:96 — "legacy" enum
type	TriangularTapeEntry	src/rules/unitdiskmapping/triangular/mod.rs:57 — internal only
type	NeighborInfo	src/rules/graph.rs:222 — re-exported but 0 consumers
type	ReductionChain	src/rules/graph.rs:1111 — return type of uncalled method

Tier 1: Test-Only (0 production callers) — Remove or make pub(crate)

Kind	Item	Location	Notes
type+ctor	ConfigIterator	src/config.rs:7	Superseded by DimsIterator
fn	HyperGraph::edges_containing()	src/topology/hypergraph.rs:113	1 test use
fn	HyperGraph::max_edge_size()	src/topology/hypergraph.rs:130	1 test use
fn	to_json_compact()	src/io.rs:101	1 test use
fn	read_file() / write_file()	src/io.rs:113,123	1 test use each
type	FileFormat + from_extension()	src/io.rs:14,23	test-only
ctor	ILPSolver::with_time_limit()	src/solvers/ilp/solver.rs:43	1 test use; ::new() has 100 uses
ctor	SpinGlass::from_graph_without_fields()	src/models/optimization/spin_glass.rs:125	1 test use
ctor	BicliqueCover::from_matrix()	src/models/specialized/biclique_cover.rs:73	1 test use; ::new has 20 uses
ctor	BoolVar::new()	src/rules/sat_maximumindependentset.rs:29	test-only; production uses ::from_literal
fn	VarBounds::non_negative()	src/models/optimization/ilp.rs:48	1 test use
fn	MaximumMatching::set_weights()	src/models/graph/maximum_matching.rs:147	1 test use
fn	TravelingSalesman::set_weights()	src/models/graph/traveling_salesman.rs:96	1 test use
fn	MinimumDominatingSet::closed_neighborhood()	src/models/graph/minimum_dominating_set.rs:80	1 test use
fn	KingsSubgraph::num_positions()	src/topology/kings_subgraph.rs:39	1 test use
fn	TriangularSubgraph::num_positions()	src/topology/triangular_subgraph.rs:42	1 test use
type	GraphTestCase / SatTestCase	src/testing/mod.rs:85,145	testing framework never used outside own tests
type	ComplexityClass	src/registry/info.rs:40	re-exported at crate root, 0 real uses
type	ProblemInfo	src/registry/info.rs:111	re-exported at crate root, 0 real uses

Tier 2: Weakly Used (2-3 test uses only) — Consider removing

Kind	Item	Location	Notes
fn	PaintShop::num_sequence()	src/models/specialized/paintshop.rs:123	redundant alias for sequence_len()
fn	BicliqueCover::count_covered_edges()	src/models/specialized/biclique_cover.rs:187	2 test uses
fn	UnitDiskGraph::bounding_box()	src/topology/unit_disk_graph.rs:147	2 test uses
fn	HyperGraph::to_graph_edges()	src/topology/hypergraph.rs:141	2 test uses
fn	is_diff_by_const()	src/rules/unitdiskmapping/alpha_tensor.rs:211	2 test uses
fn	SpinGlass::without_fields()	src/models/optimization/spin_glass.rs:90	3 test uses
fn	MaxCut::edge_weight_by_index() / edge_weight()	src/models/graph/max_cut.rs:120,125	3 test uses each
fn	BMF::is_exact()	src/models/specialized/bmf.rs:179	3 test uses

Tier 3: Dead modules/subsystems

Module	Location	Notes
truth_table	src/truth_table.rs	pub(crate), all 11 methods test-only, no production code path
testing	src/testing/mod.rs	GraphTestCase, SatTestCase, macros — all unused outside own unit tests
io file ops	src/io.rs	read_file, write_file, to_json_compact, FileFormat — none used in CLI or examples

Approach

• Tier 0: Delete dead code, make LinearConstraint::new pub(crate)
• Tier 1: Remove items or downgrade to pub(crate), update tests accordingly
• Tier 2: Case-by-case decision — some may be worth keeping for API completeness
• Tier 3: Evaluate whether entire modules should be removed or kept for future use

[GiggleLiu]

Corrections after cross-referencing with Julia UnitDiskMapping

False positives removed from Tier 0 (actually used)

The following were wrongly flagged as dead — they ARE actively used in the CLI, examples, or export pipeline:

• MatchedEntry — returned by ReductionGraph::find_best_entry(), used in src/export.rs
• NeighborInfo — returned by ReductionGraph::k_neighbors(), used in CLI (commands/graph.rs, mcp/tools.rs)
• ReductionChain — returned by reduce_along_path(), used extensively in CLI (reduce.rs, solve.rs, dispatch.rs, mcp/tools.rs) and examples
• LinearConstraint::new() — called internally by ::le()/::ge()/::eq(). Should stay pub or pub(crate), not deleted.
• MaximumSetPacking::new() — used in doctest; semantically correct unit-weight constructor. Keep.
• MinimumSetCovering::new() — same situation. Keep.

Confirmed dead UnitDiskMapping items (cross-referenced with Julia)

Rust Item	Julia Equivalent	Why Dead in Rust
print_config() / print_config_flat()	print_config(mr, config) — exported & tested in Julia	Debugging wrappers; Rust uses format_config() instead and lets callers decide output
apply_weighted_gadget_boxed_fn()	No equivalent (Julia uses multiple dispatch)	Boxed trait-object approach abandoned for enum match — more idiomatic Rust
apply_triangular_simplifier_gadgets() + 4 helpers in mod.rs	apply_simplifier_gadgets! — exported & used in Julia	Legacy duplicate; active version lives in gadgets.rs using WeightedTriTapeEntry
LegacySourceCell	No explicit equivalent	Superseded by SourceCell in gadgets.rs during refactoring
TriangularTapeEntry	No equivalent (triangular is Rust-only extension)	Superseded by WeightedTriTapeEntry in gadgets.rs

Revised Tier 0 (confirmed safe to delete)

Item	Location	Reason
MappingResult::print_config()	ksg/mapping.rs:88	Wrapper around format_config(); 0 callers
MappingResult::print_config_flat()	ksg/mapping.rs:136	Wrapper around format_config_flat(); 0 callers
apply_weighted_gadget_boxed_fn()	ksg/gadgets.rs:1647	Dead boxed dispatch wrapper
apply_triangular_simplifier_gadgets() + 4 try_apply_dangling_leg_*	triangular/mod.rs:1221-1466	Legacy duplicate of active code in gadgets.rs
LegacySourceCell	triangular/mod.rs:96	Superseded by SourceCell
TriangularTapeEntry	triangular/mod.rs:57	Superseded by WeightedTriTapeEntry

Items to keep (not useless after all)

• MaximumSetPacking::new() / MinimumSetCovering::new() — natural unit-weight API for users
• MatchedEntry, NeighborInfo, ReductionChain — actively used in CLI
• LinearConstraint::new() — internal foundation for ::le/::ge/::eq

Items needing decision (not dead, but underutilized)

• ComplexityClass + ProblemInfo — complete infrastructure but no problem implements ProblemMetadata. Either wire it up or remove.
• testing module (GraphTestCase, SatTestCase, macros) — well-designed test framework that was never adopted. Either start using the macros or remove.
• ConfigIterator — strictly less general than DimsIterator; redundant but harmless.