Dual Variables Dimension Clarification

[ocots]

See #105.

[github-actions]

Breakage test results
Date: 2025-12-17 15:56:45

Name	Latest	Stable
CTDirect	compat: v0.6.9	compat: v0.6.9
CTFlows	compat: v0.6.9	compat: v0.6.9
OptimalControl	compat: v0.6.9	compat: v0.6.9

[ocots]

🎯 Action Plan: PR #240 - Dual Variables Dimension Clarification

Date: 2025-12-17
PR: #240 by @ocots | Branch: 105-dev-dual-variables → main
State: DRAFT | Linked Issue: #105

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📋 Overview

Issue Summary: Clarify dual variable semantics when multiple constraints are declared on the same state/control component. Question: should state_constraints_ub_dual(t) return dimension 3 (constraints count) or 2 (state dimension)?

PR Summary: Draft PR created as placeholder to link to issue #105. Currently contains only a trivial newline change. Real implementation not yet started.

Status: Draft / Needs full implementation

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🔍 Project Context

Project: CTModels.jl v0.7.0 (Julia)
Current branch: 105-dev-dual-variables
CI Status: ✅ All 21 checks passing

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🎯 Gap Analysis

✅ Completed Requirements

(None - implementation not started)

❌ Missing Requirements (from Issue #105 planning report)

Task	Description	Status
T1	Detect duplicate box constraints and emit warning	❌ Not started
T2	Document dual dimension semantics in docstrings	❌ Not started

➕ Additional Work Done

• PR created and linked to issue
• All CI checks passing

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🧪 Test Status

Overall: ✅ All passing (no new changes to test)

CI Checks: 21/21 passing

• CI tests (Julia 1.10, 1.12): ✅
• Breakage tests (CTDirect, CTFlows, OptimalControl): ✅
• Documentation, SpellCheck, Formatter: ✅

Local Tests: Not run (no code changes)

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📝 Review Feedback

Reviews: None
Comments: 1 (github-actions bot - breakage test results)

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🔧 Code Quality Assessment

Current PR: No substantive code changes to assess.

Required Implementation (from issue planning):

• src/ocp/model.jl: Add duplicate index detection in append_box_constraints!
• src/ocp/solution.jl: Update build_solution docstring

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📋 Proposed Action Plan

🔴 Critical Priority (blocking merge)

1. Implement T1: Duplicate constraint detection

   • Why: Core feature requested in issue
   • Where: src/ocp/model.jl - append_box_constraints! or build(constraints)
   • Estimated effort: Small
   • Details: Detect when a component index is repeated in box constraints, emit @warn

2. Implement T2: Document dual dimension semantics

   • Why: Clarify API behavior
   • Where: src/ocp/solution.jl - docstring of build_solution
   • Estimated effort: Small
   • Details: Document that state_constraints_*_dual has dimension = state dimension

🟡 High Priority (should do before merge)

1. Add unit tests for duplicate constraint warning

   • Why: Verify warning is emitted
   • Where: test/ocp/test_constraints.jl
   • Estimated effort: Small

2. Update PR with meaningful commit message

   • Why: Current "foo" commit is placeholder
   • Where: Git history
   • Estimated effort: Trivial

🟢 Medium Priority (nice to have)

1. Add documentation in user guide
   • Why: Issue mentions updating tutorial docs
   • Where: docs/ or external OptimalControl.jl tutorial
   • Estimated effort: Small

🔵 Low Priority (future work)

1. Consider CTDirect/CTParser integration
   • Why: Issue discussion mentions parse_docp_dual updates
   • Can be deferred to: Separate PR after this is merged

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💡 Recommendations

Immediate next steps:

1. Implement duplicate constraint detection with warning (T1)
2. Update docstrings (T2)
3. Add test for warning emission
4. Squash/amend commit with proper message

Before merging:

• All Critical items resolved
• Tests passing
• CI checks passing (currently ✅)
• Reviews approved
• Documentation updated
• Remove Draft status

After merge:

• Update related packages (CTParser, CTDirect) if needed

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⏱️ Estimated Effort

To complete Critical + High: ~1-2 hours
To complete all: ~2-3 hours

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📂 Changed Files Summary (Current PR)

File	Changes	Notes
src/CTModels.jl	+1/-1	Trivial newline change (placeholder)

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🔗 Key References

• Issue [Dev] Dual variables #105 Planning Report: Comment by @ocots (Dec 16, 2025)
• Decision: Option A - Dual dimension = state dimension, with warning for duplicates
• Files to modify: src/ocp/model.jl, src/ocp/solution.jl

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Next Step: Please review this plan and advise:

• Agree with priorities?
• Ready to start implementation?
• Any changes needed?