FESADev/phases/1-linear-static-mitc4/step6.md

Step 6: analysis-model-dof-manager

Sprint Contract

Objective

Implement AnalysisModelBuilder and DofManager for one active linear static step with six-DOF nodes, constrained/free mapping, equation numbering, sparse-pattern input, and full/reduced vector reconstruction.

Required Reading

• /AGENTS.md
• /PROGRESS.md
• /PLAN.md
• /docs/README.md
• /docs/HARNESS_ENGINEERING.md
• /docs/PRD.md
• /docs/ARCHITECTURE.md
• /docs/ADR.md
• /docs/NUMERICAL_CONVENTIONS.md
• /phases/1-linear-static-mitc4/step5.md

Scope

• Build an AnalysisModel active view from validated Domain.
• Assign six shell DOFs per active node in documented order.
• Apply fixed boundary conditions by constrained DOF elimination.
• Produce int64 equation numbers for free DOFs and mappings for constrained DOFs.
• Provide reconstruction helpers between reduced vectors and full vectors.

Allowed Files

• include/**
• src/**
• tests/**
• PLAN.md
• PROGRESS.md
• phases/1-linear-static-mitc4/index.json

Explicit Non-Goals

• Do not assemble element stiffness or loads.
• Do not store equation ids on Node or Element objects.
• Do not solve linear systems or write HDF5 results.

Tests To Write First

• DOF numbering tests for simple models with all six components.
• Constrained/free partition tests for fixed boundary conditions.
• Reduced/full reconstruction tests including constrained values set to zero for Phase 1.
• Sparse-pattern input tests using active element connectivity without assembling values.

Reference Artifacts

• None.

Acceptance Commands

python scripts/validate_workspace.py

Evaluator Checklist

• DofManager owns global equation numbering.
• ids, sparse indices, and equations remain int64-based.
• Fixed constraints are handled by elimination, not penalty.
• Reconstruction supports later full-vector RF recovery.

Handoff Requirements

• Record DOF behavior, tests, and validation in PROGRESS.md.
• Update PLAN.md only for future work or resolved blockers.
• Update the matching phase index entry: use completed with a one-line summary, or blocked with blocked_reason, or error with error_message.

Verification

1. Run the acceptance command.
2. Inspect tests for constrained/free and full/reduced mapping edge cases.

Do Not

• Do not make constrained DOF elimination depend on reduced-only reaction recovery.