Fix #184: Add MinimumMultiwayCut model by hmyuuu · Pull Request #221 · CodingThrust/problem-reductions

hmyuuu · 2026-03-10T10:06:57Z

Summary

Add MinimumMultiwayCut problem model — minimum-weight edge set whose removal disconnects all terminal pairs
Edge-based binary optimization with BFS feasibility check
Cao, Chen & Wang (2013) complexity: O(1.84^k * n^3)
CLI support: dispatch, create with --terminals/--edge-weights/--graph, solve, evaluate
Paper problem-def entry with formal definition, background, and CeTZ example figure
8 unit tests, example program, schema/graph exports updated

Co-authored with Claude (opus-4.6)

Test plan

All unit tests pass (cargo test minimum_multiway_cut)
Example runs correctly (cargo run --example minimummultiwaycut)
make check passes (fmt + clippy + test)
Paper builds (make paper)
CLI workflow verified: pred create → pred inspect → pred solve --solver brute-force → pred evaluate

Fixes #184

Co-authored-by: Claude <noreply@anthropic.com>

Implement the Minimum Multiway Cut problem — find minimum-weight edge set whose removal disconnects all terminal pairs. Edge-based binary variables with BFS feasibility check. Solved via BruteForce. - Model struct with Problem/OptimizationProblem traits - CLI dispatch and alias (mmc) - 10 unit tests + example program - Regenerated schemas and reduction graph Co-authored-by: Claude <noreply@anthropic.com>

…hrust#184) - Add `pred create MinimumMultiwayCut` with --terminals, --edge-weights, --graph - Add problem-def entry in Typst paper with example figure - Improve `pred solve` error: suggest --solver brute-force when no ILP path - Remove spurious MMC alias (not a well-known abbreviation) - Regenerate reduction graph and schema exports - Delete implementation plan Co-authored-by: Claude <noreply@anthropic.com>

hmyuuu · 2026-03-10T10:24:25Z

Agentic Test Results

Ran /test-feature with two simulated user personas to validate the MinimumMultiwayCut implementation end-to-end.

Personas

Rust developer — moderate experience, first time using the crate, wants to model a network isolation problem
Researcher — comfortable with CLI, not a Rust developer, wants to explore/create/solve from terminal

Verdict: pass

Feature	Discoverable	Setup	Works	Expected Outcome Met	Doc Quality
Library API	yes	yes	yes	yes	good
CLI tool	yes (via `pred list`)	yes	yes	yes	good

Issues Found & Fixed During Testing

[Fixed] pred create had no MinimumMultiwayCut support → Added --terminals flag, dispatch handler, problem-specific help
[Fixed] pred solve error message → Now suggests --solver brute-force when no ILP reduction path exists
[Fixed] pred create --help missing MMC entry → Added to "Flags by problem type" section
[Fixed] Spurious MMC alias → Removed (not a well-known abbreviation)
[Fixed] Edge weight ordering undocumented on new() → Added doc comment explaining weight-to-edge correspondence and config encoding
[Fixed] CLI docs stale → Updated pred list output (17 → 25 types), added MMC create example, added CVP/MaxMatching aliases to table

All issues resolved — no remaining items.

- Document edge weight ordering and config encoding on `new()` docstring - Add MinimumMultiwayCut create example to CLI docs - Update `pred list` output in CLI docs (17 → 25 problem types) - Add CVP and MaxMatching aliases to CLI docs alias table Co-authored-by: Claude <noreply@anthropic.com>

Use config.get(idx) and edge_weights.get(idx) instead of direct indexing to avoid panics on malformed input, matching the codebase convention used by MaximumIndependentSet, TravelingSalesman, etc. Made-with: Cursor

hmyuuu · 2026-03-10T18:17:27Z

examples/minimummultiwaycut.rs

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Copilot

Pull request overview

Adds a new graph optimization model, MinimumMultiwayCut, to the core library and wires it through the CLI + documentation pipeline so it can be created/serialized/used from pred and showcased via examples/tests.

Changes:

Introduce MinimumMultiwayCut model (schema registration, variant declaration, feasibility + objective evaluation).
Integrate the new model into CLI aliasing/dispatch and pred create, plus add a runnable example and test coverage.
Regenerate/update docs artifacts (schemas + reduction graph) and extend the paper/CLI documentation to include the new problem.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/suites/examples.rs	Adds the new `minimummultiwaycut` example to the example test suite.
src/unit_tests/models/graph/minimum_multiway_cut.rs	New unit tests for creation, evaluation, brute force solving, serialization, and edge cases.
src/models/mod.rs	Re-exports `MinimumMultiwayCut` from the models module.
src/models/graph/mod.rs	Registers and re-exports the new graph model in the graph module.
src/models/graph/minimum_multiway_cut.rs	New implementation of the Minimum Multiway Cut optimization problem + schema/variants.
src/lib.rs	Exposes `MinimumMultiwayCut` through the crate prelude.
problemreductions-cli/src/problem_name.rs	Adds CLI alias resolution for `minimummultiwaycut`.
problemreductions-cli/src/dispatch.rs	Enables load/serialize dispatch for `MinimumMultiwayCut` and improves the “no ILP path” hint.
problemreductions-cli/src/commands/create.rs	Adds `pred create MinimumMultiwayCut` support and parses `--terminals`.
problemreductions-cli/src/cli.rs	Documents `MinimumMultiwayCut` flags and adds `--terminals` argument.
examples/minimummultiwaycut.rs	New runnable example demonstrating brute-force solving + JSON export.
docs/src/reductions/reduction_graph.json	Adds the new problem variant node to the generated reduction graph.
docs/src/reductions/problem_schemas.json	Adds the new problem schema entry to the generated schemas.
docs/src/cli.md	Updates CLI docs (`pred list` output sample, examples, alias table).
docs/paper/references.bib	Adds citations for Minimum Multiway Cut complexity/algorithms.
docs/paper/reductions.typ	Adds a formal definition + example figure/text for Minimum Multiway Cut.

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src/models/graph/minimum_multiway_cut.rs

+    // Build adjacency list from non-cut edges
+    let mut adj: Vec<Vec<usize>> = vec![vec![]; n];
+    for (idx, (u, v)) in edges.iter().enumerate() {
+        if config.get(idx).copied().unwrap_or(0) == 0 {
+            adj[*u].push(*v);
+            adj[*v].push(*u);
+        }
+    }
+
+    // BFS from each terminal; if a terminal is already visited by a previous
+    // terminal's BFS, they share a component => infeasible.
+    let mut component = vec![usize::MAX; n];
+    for (comp_id, &t) in terminals.iter().enumerate() {
+        if component[t] != usize::MAX {
+            return false;
+        }
+        let mut queue = VecDeque::new();
+        queue.push_back(t);
+        component[t] = comp_id;
+        while let Some(u) = queue.pop_front() {
+            for &v in &adj[u] {
+                if component[v] == usize::MAX {
+                    component[v] = comp_id;
+                    queue.push_back(v);
+                }
+            }
+        }
+    }


problemreductions-cli/src/commands/create.rs

+/// Parse `--terminals` as a comma-separated list of vertex indices.
+fn parse_terminals(args: &CreateArgs) -> Result<Vec<usize>> {
+    let terminals_str = args
+        .terminals
+        .as_deref()
+        .ok_or_else(|| anyhow::anyhow!("MinimumMultiwayCut requires --terminals (e.g., 0,2,4)"))?;
+
+    terminals_str
+        .split(',')
+        .map(|s| {
+            s.trim()
+                .parse::<usize>()
+                .map_err(|e| anyhow::anyhow!("Invalid terminal index '{}': {}", s.trim(), e))
+        })
+        .collect()
+}


Resolve additive merge conflicts: both sides added new problem models. Include MinimumMultiwayCut (PR) alongside all new models from main (HamiltonianPath, GraphPartitioning, OptimalLinearArrangement, etc.). For dispatch.rs and problem_name.rs, adopt main's registry-based dynamic dispatch. For JSON artifacts, use main's version with MinimumMultiwayCut entries added. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add missing fields (display_name, aliases, dimensions) required by updated ProblemSchemaEntry struct, and add opt/default to declare_variants. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Per reviewer comment: example binaries should be utility/export tools or pedagogical demos, not per-model files. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

codecov · 2026-03-15T10:41:06Z

Codecov Report

❌ Patch coverage is 96.96970% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.85%. Comparing base (5bd4da9) to head (5c9bcd7).

Files with missing lines	Patch %	Lines
src/models/graph/minimum_multiway_cut.rs	93.68%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #221      +/-   ##
==========================================
- Coverage   96.86%   96.85%   -0.01%     
==========================================
  Files         264      266       +2     
  Lines       35196    35394     +198     
==========================================
+ Hits        34091    34282     +191     
- Misses       1105     1112       +7

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- Add MinimumMultiwayCut to trait_consistency tests - Add canonical model example in example_db - Strengthen brute-force test to verify specific optimal config - Strengthen short_config test assertions - Regenerate problem_schemas.json Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

zazabap · 2026-03-15T10:52:37Z

Review Pipeline Report

Check	Result
Copilot comments	approved, no actionable inline comments
Issue/human comments	3 checked, 1 already fixed (bounds checking), 1 addressed (example file removed)
Structural review	18/18 passed (after fixes)
CI	green
Agentic test	passed (2 personas: Rust dev + researcher)
Needs human decision	none
Board	Ready → Under review → Final review

Fixes applied

Merged origin/main and resolved 12 merge conflicts
Updated ProblemSchemaEntry to include new required fields (display_name, aliases, dimensions)
Added opt/default to declare_variants! macro call
Removed per-model example file (examples/minimummultiwaycut.rs) per reviewer comment
Added MinimumMultiwayCut to trait_consistency tests (both check_problem_trait and direction)
Added canonical model example in example_db (canonical_model_example_specs)
Strengthened brute-force test to verify specific optimal config [1,0,0,1,1,0] is among solutions
Strengthened short_config test to assert SolutionSize::Invalid instead of != Valid(0)
Regenerated problem_schemas.json

Remaining issues for final review

None.

🤖 Generated by review-pipeline

hmyuuu and others added 3 commits March 10, 2026 18:10

Add plan for CodingThrust#184: MinimumMultiwayCut model

c98aab7

Co-authored-by: Claude <noreply@anthropic.com>

hmyuuu force-pushed the issue-184-minimum-multiway-cut branch from 13ffca2 to 4e30437 Compare March 10, 2026 10:22

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fix: use defensive bounds checking in MinimumMultiwayCut evaluate

c81bcac

Use config.get(idx) and edge_weights.get(idx) instead of direct indexing to avoid panics on malformed input, matching the codebase convention used by MaximumIndependentSet, TravelingSalesman, etc. Made-with: Cursor

hmyuuu commented Mar 10, 2026

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examples/minimummultiwaycut.rs Outdated

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zazabap requested a review from Copilot March 15, 2026 10:09

Copilot started reviewing on behalf of zazabap March 15, 2026 10:10 View session

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zazabap and others added 3 commits March 15, 2026 10:32

fix: resolve merge conflicts with main and update ProblemSchemaEntry

0310fd8

Add missing fields (display_name, aliases, dimensions) required by updated ProblemSchemaEntry struct, and add opt/default to declare_variants. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

chore: remove per-model example file (not needed)

c1e95f9

Per reviewer comment: example binaries should be utility/export tools or pedagogical demos, not per-model files. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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Fix #184: Add MinimumMultiwayCut model#221

Fix #184: Add MinimumMultiwayCut model#221
hmyuuu wants to merge 9 commits intoCodingThrust:mainfrom
hmyuuu:issue-184-minimum-multiway-cut

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Verdict: pass

Issues Found & Fixed During Testing

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