forked from 1b-agent/fieldcraft-upstream
jyvikoandClaude Opus 5.5
a30d0b5c5b
Segment-to-segment penalty contact between element faces: each secondary face and each main face facing it are projected onto the secondary face's plane, split into triangles, clipped (Sutherland–Hodgman) and integrated with a three-point rule per sub-triangle (Puso–Laursen segmentation, the penalty at the integration points as Fischer–Wriggers), so a uniform pressure gives the consistent nodal forces on both meshes and the contact patch test passes on non-matching meshes. Every contact runs both ways at half the penalty: pairs with each surface as the secondary, general and self contact face against face. A bucket grid of face boxes every increment, faces integrated in parallel and their forces added in face order: the same numbers on any thread count. The penalty per area ε = s γ min(m/A)/Δt² comes from the lumped masses, each node's directional area and the stable increment, bounded by Gershgorin's row sums so contact never shortens the increment. Coulomb friction with exponential decay by a regularised return map at the secondary nodes; rigid walls take Coulomb impulses. Contact work and friction dissipation join the energy balance; each contact reports its peak force, first and last contact, deepest penetration, friction and the nodes adjusted at the start (initial penetrations adjusted strain-free or refused with the node, face and depth); a cap on contact faces. Verified (crates/explicit/tests/contact.rs, tests/oracle/explicit-*): colliding bars (2L/c +1.2%, ρcAv₀/2, KE kept to 0.005%, contact energy back to 8e-5 of it), blocks sliding to a stop on a rigid wall and on a plate under constant and decaying friction (0.005–0.2%), the patch test (σ_zz uniform to 0.06%), two spheres colliding against Hertz (peak +2.3%, duration −0.4%; the oracle case waits for a graded sphere mesher), a free body untouched by general contact, determinism across threads. Oracle measures gain `over` (ratios). Existing fixtures do not move. Co-Authored-By: Claude Opus 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm
94 lines
6.2 KiB
Markdown
94 lines
6.2 KiB
Markdown
# Verification and validation
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Every solver capability is checked against three kinds of reference, and every accepted result is
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frozen so it cannot drift.
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| Kind | What it checks | Sources |
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|---|---|---|
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| Theory | The code solves the equations right | Closed-form solutions (beams, plates, Lamé, Kirsch, waves, shocks, Poiseuille…), patch tests, convergence rates, mesh invariants |
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| Experiment | The model predicts reality | Measurements published in papers and reports (Taylor bar, cavity and cylinder flows, FSI experiments…) |
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| Published benchmarks | Agreement with established codes on standard problems | NAFEMS benchmarks, vendor benchmark and verification manuals (e.g. Abaqus Benchmarks and Verification manuals), other published reference solutions |
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Rules:
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- Each case is **our own model** of the problem, built from the published description (geometry,
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material, loads, boundary conditions). We never run a commercial product and never copy its
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input files, manual text or figures; only the published numbers are used, with a citation.
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- Each case lives in `tests/oracle/<case>/`:
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- `recipe.json` — the model as FieldCraft commands (or a SolidCraft recipe for geometry);
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- `expected.json` — the reference values with `kind` (theory | experiment | benchmark),
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`source` (citation: document, table or figure, page), `quantity`, `value`, `tolerance` and
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the reason for that tolerance (mesh, measurement scatter, model differences);
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- `fixture.json` — FieldCraft's accepted result, written by `cargo xtask oracle --bless <case>`
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only after the case passes against `expected.json`.
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- `cargo xtask oracle` runs every case, compares with `expected.json` (pass/fail with error) and
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with `fixture.json` (any change beyond the fixture tolerance fails CI, even if the reference
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still passes), and writes `docs/oracle.md` with the table of cases, sources, errors and status.
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- A fixture is updated only deliberately (`--bless`), in a PR that says why the result moved
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(a better element, a finer default mesh), never to hide a regression.
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- The theory suite is the gate for every merge; experiment and benchmark cases run in CI too, with
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their cited tolerances.
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## The case format
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`cargo xtask oracle` builds `fieldcraft-testkit`'s `oracle` binary (release) once and runs every
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case through the command engine; the results are in [oracle.md](oracle.md).
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```
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cargo xtask oracle # every case; writes docs/oracle.md
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cargo xtask oracle --case nafems-le1 # one case (repeatable); docs untouched
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cargo xtask oracle --bless nafems-le1 # freeze a passing case's results (or --bless all)
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cargo xtask oracle --quick # skip cases marked "slow"
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```
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- `recipe.json` is a script `fieldcraft-cli run` also accepts: a JSON array of
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`{"command", "params"}`; a step may carry an `"id"` so a quantity can read its output. Meshes
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come from `mesh.block` (mapped hex, tet or wedge blocks with arcs and elliptical edges, named
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faces, edges and vertices that sets select), `mesh.tet.generate`, or nodes and elements written
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one by one; once structured and automatic meshers land, cases may use them.
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- `design.json` (optional) is a SolidCraft script that builds the geometry, opened before the
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recipe (the test corpus's recipe form).
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- `expected.json`:
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```json
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{"title": "…", "kind": "theory|benchmark|experiment",
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"source": "document, section/table/figure, page",
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"status": "active|pending", "requires": "the capability a pending case waits for",
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"slow": false,
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"quantities": [{"id": "syy_D", "quantity": "σ_yy at D (2, 0)",
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"measure": {"command": "solve.probe", "params": {"step": "Load", "at": [[2, 0, 0]]}, "pointer": "/nodes/0/stress/1"},
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"value": 92.7, "tolerance": {"relative": 0.01}, "reason": "why this tolerance",
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"known_failure": "optional: why FieldCraft misses the reference today"}]}
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```
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A measure reads a JSON pointer either from a recipe step's output (`"from": "<id>"`) or from a
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command run after the recipe (`"command"`, `"params"`); an optional `"scale"` multiplies it, and
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an optional `"over"` (a measure of its own) divides it by another number of the same run, for
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ratios such as the stress in one element over the stress in another.
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A tolerance is `relative` (of the reference), `absolute`, both, or `"exact": true`. A pending
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case cites its reference values (or `null` until transcribed) and has no recipe yet.
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- `fixture.json` holds each passing quantity's accepted `value` and its `band`
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(10⁻⁹ of the larger of value and reference, plus 10⁻³ of an absolute tolerance; a quantity whose
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reference is zero, which is rounding noise, keeps its absolute tolerance as its band; an
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ill-conditioned quantity may set a wider `fixture_relative` with a `fixture_reason`; a quantity
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that depends on a mesh generated from geometry, which is not bit-identical across platforms, sets
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`"fixture": false` with a `fixture_reason` and is gated by its reference tolerance alone): the result is
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deterministic, the band only absorbs last-digit differences of the system maths library.
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The run fails when a quantity misses its reference (unless it is a `known_failure`, which is
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listed in oracle.md with its reason), when a known failure starts passing (remove the mark),
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when a result leaves its fixture band, when a passing quantity has no fixture, or when a case
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cannot run.
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## Adding cases for a new capability
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Every capability that lands brings its oracle cases in the same pull request:
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1. Turn the pending cases that waited for it into active ones (write `recipe.json`, drop
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`status`/`requires`, add `measure` and `tolerance` with its reason to each quantity), and add
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theory cases for its closed-form solutions (patch test and convergence for an element; the
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analytic problem for a load, constraint or procedure).
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2. Choose meshes that are converged well inside the tolerance (show the refinement in the case's
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README), or the mesh a benchmark prescribes.
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3. Run `cargo xtask oracle --case <name>`; when it passes, `--bless <name>`; commit the case, its
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fixture and the regenerated docs/oracle.md.
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4. A case that misses its reference stays honest: keep the tolerance its reason supports and add
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`known_failure` with what is missing. Never widen a tolerance to make a case pass.
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