FESADev/phases/1-linear-static-mitc4-rebaseline/step12.md

Sprint Contract: Assembly Sparse Solver Path

Objective

Rebuild or verify full-space assembly, reduced free-DOF solve path, solver adapter boundary, and full-vector reaction recovery using the rebuilt MITC4 kernel.

Required Reading

• /AGENTS.md
• /docs/ARCHITECTURE.md
• /docs/ADR.md
• /docs/NUMERICAL_CONVENTIONS.md
• /docs/MITC4_FORMULATION.md

Scope

• Assemble global stiffness and external load vectors.
• Preserve full-space data for RF = K_full * U_full - F_full.
• Apply constrained DOF elimination via DofManager.
• Use the current deterministic test solver or adapter boundary; keep MKL behind a future adapter.

Allowed Files

• include/
• src/
• tests/
• PLAN.md
• PROGRESS.md

Explicit Non-Goals

• Do not expose MKL or TBB APIs directly in solver core.
• Do not compare stored Abaqus references yet.
• Do not compute reactions from reduced equations.

Tests To Write First

• Small assembled system tests with known displacement.
• Full-vector RF recovery tests.
• Constrained/free projection tests through assembly.
• Singular solve diagnostic tests.
• Sparse pattern deterministic ordering tests if sparse structure exists.

Reference Artifacts

• None.

Acceptance Commands

python scripts/validate_workspace.py

Evaluator Checklist

• Full-space stiffness/load/displacement are available or reconstructable for reactions.
• Solver adapter boundary is preserved.
• Singular failures remain actionable.

Handoff Requirements

• Record assembly and reaction readiness in PROGRESS.md.

Do Not

• Do not let elements own global equation ids.