feat(phase4): HyperIdeal Newton solver, SparseQR fallback, examples, docs

Phase 4 complete — 87 CGAL tests pass, 2 skipped.

Newton solver (phase4a):
- hyper_ideal_hessian.hpp: symmetric FD Hessian (O(ε²), PSD by convexity)
- newton_hyper_ideal(): Newton + backtracking for the HyperIdeal functional
- detail::solve_with_fallback(): optional bool* fallback_used parameter
- solve_linear_system(): public API exposing LDLT→SparseQR fallback

SparseQR fallback tests (SparseQRFallback.*):
- FullRankSystem_CorrectSolution: LDLT path, fallback_used=false
- SingularMatrix_FallbackActivated: zero-pivot → QR activated, fallback_used=true
- Euclidean_ClosedMeshNoPinConverges: gauge-mode null space handled via QR

HyperIdeal Newton tests (NewtonSolver.HyperIdeal_*):
- ConvergesTriangleAllVariable, ResultFieldsConsistent,
  ConvergesTetrahedron, SparseQRFallbackNoCrash
- Natural-target base point (b=1.0, a=0.5) — x=0 is degenerate in log-space

Pipeline tests (test_pipeline.cpp):
- End-to-end: all three geometries, mesh I/O round-trip, solve+export

Example programs (code/examples/):
- example_euclidean.cpp:   headless Euclidean pipeline
- example_hyper_ideal.cpp: headless HyperIdeal pipeline
- example_viewer.cpp:      interactive libigl viewer with jet colour map

README:
- Mathematical scope table: C++ vs Java original (18 rows)
- "For mathematicians" section: mental model, step-by-step new-functional
  guide, half-edge traversal snippets, recommended reading

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Tarik Moussa
2026-05-13 00:11:25 +02:00
parent e70689d29f
commit 3f124eb071
12 changed files with 1798 additions and 165 deletions

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@@ -30,6 +30,9 @@ add_executable(conformallab_cgal_tests
# ── Phase 4b: Mesh I/O (CGAL::IO) ─────────────────────────────────────
test_mesh_io.cpp
# ── Phase 4c: End-to-end pipeline + user examples ─────────────────────
test_pipeline.cpp
)
target_include_directories(conformallab_cgal_tests SYSTEM PRIVATE

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@@ -20,7 +20,9 @@
#include "conformal_mesh.hpp"
#include "mesh_builder.hpp"
#include "hyper_ideal_functional.hpp"
#include "hyper_ideal_hessian.hpp"
#include <gtest/gtest.h>
#include <Eigen/Dense>
#include <cmath>
#include <vector>
@@ -52,9 +54,19 @@ static std::vector<double> make_x_all_variable(
// @Ignore in Java: no Hessian implemented
// ════════════════════════════════════════════════════════════════════════════
TEST(HyperIdealFunctional, GradientCheck_Hessian)
TEST(HyperIdealFunctional, HessianSymmetryCheck)
{
GTEST_SKIP() << "@Ignore in Java Hessian not implemented in the functional";
// Hessian is now implemented (numerical FD). Verify it is symmetric.
auto mesh = make_triangle();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
std::vector<double> x(static_cast<std::size_t>(n), 0.5);
auto H = hyper_ideal_hessian_sym(mesh, x, maps);
Eigen::MatrixXd Hd(H);
EXPECT_NEAR((Hd - Hd.transpose()).norm(), 0.0, 1e-8)
<< "HyperIdeal Hessian must be symmetric";
}
// ════════════════════════════════════════════════════════════════════════════

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@@ -1,12 +1,14 @@
// test_newton_solver.cpp
//
// Phase 4a — Newton solver tests.
// Phase 4 — Newton solver tests.
//
// Design principle:
// We test convergence to a KNOWN equilibrium. For the spherical tetrahedron
// x* = 0 is built-in (G(0) ≈ 0 by construction). For Euclidean meshes we
// use "natural theta": set theta_v[v] = actual angle sum at x=0, which makes
// x* = 0 the exact equilibrium by definition.
// For HyperIdeal we use the same "natural target" trick at a valid base point
// (b=1.0, a=0.5), since x=0 is degenerate for the HyperIdeal functional.
//
// Tests:
// Spherical:
@@ -19,12 +21,26 @@
// 5. Converges (triangle, 1 pinned vertex, natural theta).
// 6. Converges (quad strip, 1 pinned vertex, natural theta).
// 7. Converges with explicitly chosen mixed pinned/variable layout.
//
// HyperIdeal:
// 8. Converges on triangle (all variable, natural targets).
// 9. Result fields self-consistent.
// 10. Converges on tetrahedron (10 DOFs, larger mesh).
// 11. SparseQR: result consistent (valid starting region).
//
// SparseQR fallback (direct unit tests):
// 12. solve_linear_system recovers correct solution on rank-deficient matrix.
// 13. solve_linear_system sets fallback_used=true on a singular matrix.
// 14. Euclidean Newton on closed tetrahedron (no pinned vertex) converges
// via SparseQR gauge-mode handling.
#include "conformal_mesh.hpp"
#include "mesh_builder.hpp"
#include "euclidean_functional.hpp"
#include "spherical_functional.hpp"
#include "hyper_ideal_functional.hpp"
#include "newton_solver.hpp"
#include <Eigen/Dense>
#include <gtest/gtest.h>
#include <cmath>
#include <vector>
@@ -233,3 +249,252 @@ TEST(NewtonSolver, Euclidean_ConvergesMixedPinned)
"grad_inf_norm = " << res.grad_inf_norm;
EXPECT_LT(res.grad_inf_norm, 1e-8);
}
// ════════════════════════════════════════════════════════════════════════════
// Helper: set HyperIdeal target angles to actual sums at a non-degenerate
// base point (b_base, a_base), making that point the equilibrium x*.
//
// Note: x = 0 is degenerate for the HyperIdeal functional (log-space; the
// functional requires b_i > 0 / a_e > 0). We therefore choose a valid base
// point, evaluate G there, and absorb G into the targets so that G(xbase) = 0.
// Newton tests then start from a perturbation of xbase.
//
// Returns xbase so callers can construct a perturbed starting point.
// ════════════════════════════════════════════════════════════════════════════
static std::vector<double> set_natural_hyper_ideal_targets(
ConformalMesh& mesh, HyperIdealMaps& maps, int n,
double b_base = 1.0, double a_base = 0.5)
{
const auto sz = static_cast<std::size_t>(n);
std::vector<double> xbase(sz, 0.0);
for (auto v : mesh.vertices()) {
int iv = maps.v_idx[v];
if (iv >= 0) xbase[static_cast<std::size_t>(iv)] = b_base;
}
for (auto e : mesh.edges()) {
int ie = maps.e_idx[e];
if (ie >= 0) xbase[static_cast<std::size_t>(ie)] = a_base;
}
// G = Σβ - theta_target (initial target = 0 → G = Σβ = "actual" angles)
auto G = evaluate_hyper_ideal(mesh, xbase, maps, /*energy=*/false).gradient;
// Set target := actual so that G(xbase) = actual - target = 0
for (auto v : mesh.vertices()) {
int iv = maps.v_idx[v];
if (iv < 0) continue;
maps.theta_v[v] += G[static_cast<std::size_t>(iv)];
}
for (auto e : mesh.edges()) {
int ie = maps.e_idx[e];
if (ie < 0) continue;
maps.theta_e[e] += G[static_cast<std::size_t>(ie)];
}
return xbase;
}
// ════════════════════════════════════════════════════════════════════════════
// HyperIdeal 1 — Triangle, all DOFs variable, converges from perturbation
// ════════════════════════════════════════════════════════════════════════════
TEST(NewtonSolver, HyperIdeal_ConvergesTriangleAllVariable)
{
auto mesh = make_triangle();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
// xbase = (b=1.0, a=0.5) is the equilibrium after natural-target setup.
auto xbase = set_natural_hyper_ideal_targets(mesh, maps, n);
// Perturb by +0.2 uniformly
std::vector<double> x0 = xbase;
for (auto& v : x0) v += 0.2;
auto res = newton_hyper_ideal(mesh, x0, maps, /*tol=*/1e-7, /*max_iter=*/100);
EXPECT_TRUE(res.converged)
<< "Newton (HyperIdeal, triangle) should converge; "
"grad_inf_norm = " << res.grad_inf_norm;
EXPECT_LT(res.grad_inf_norm, 1e-7);
}
// ════════════════════════════════════════════════════════════════════════════
// HyperIdeal 2 — Result fields self-consistent
// ════════════════════════════════════════════════════════════════════════════
TEST(NewtonSolver, HyperIdeal_ResultFieldsConsistent)
{
auto mesh = make_triangle();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
auto xbase = set_natural_hyper_ideal_targets(mesh, maps, n);
std::vector<double> x0 = xbase;
for (auto& v : x0) v += 0.1;
auto res = newton_hyper_ideal(mesh, x0, maps, /*tol=*/1e-7, /*max_iter=*/100);
EXPECT_EQ(static_cast<int>(res.x.size()), n);
// Reported grad_inf_norm must match re-computed gradient at res.x
auto G = evaluate_hyper_ideal(mesh, res.x, maps, false).gradient;
double actual_inf = 0.0;
for (double v : G) actual_inf = std::max(actual_inf, std::abs(v));
EXPECT_NEAR(actual_inf, res.grad_inf_norm, 1e-9);
}
// ════════════════════════════════════════════════════════════════════════════
// HyperIdeal 3 — Tetrahedron (10 DOFs): 4 vertex b-vals + 6 edge a-vals
// ════════════════════════════════════════════════════════════════════════════
TEST(NewtonSolver, HyperIdeal_ConvergesTetrahedron)
{
auto mesh = make_tetrahedron();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
auto xbase = set_natural_hyper_ideal_targets(mesh, maps, n);
// Perturb by +0.15
std::vector<double> x0 = xbase;
for (auto& v : x0) v += 0.15;
auto res = newton_hyper_ideal(mesh, x0, maps, /*tol=*/1e-7, /*max_iter=*/200);
EXPECT_TRUE(res.converged)
<< "Newton (HyperIdeal, tetrahedron) should converge; "
"grad_inf_norm = " << res.grad_inf_norm;
EXPECT_LT(res.grad_inf_norm, 1e-7);
}
// ════════════════════════════════════════════════════════════════════════════
// HyperIdeal 4 — SparseQR fallback: solver returns a result (no crash)
//
// With all targets = 0 the equilibrium is not at x=0 but the solver should
// at minimum not crash and return a consistent result struct.
// ════════════════════════════════════════════════════════════════════════════
TEST(NewtonSolver, HyperIdeal_SparseQRFallbackNoCrash)
{
auto mesh = make_triangle();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
// Leave targets at their default (0): solver tries to solve but the
// "equilibrium" is at some unknown x*. With valid starting point the
// Hessian is positive-definite and the solver should not crash.
// We don't assert convergence — just that the result struct is consistent.
std::vector<double> x0(static_cast<std::size_t>(n), 1.0);
// Mix vertex / edge DOFs: b=1.0, a=0.5 (valid region of the functional)
for (auto e : mesh.edges()) {
int ie = maps.e_idx[e];
if (ie >= 0) x0[static_cast<std::size_t>(ie)] = 0.5;
}
auto res = newton_hyper_ideal(mesh, x0, maps, /*tol=*/1e-7, /*max_iter=*/50);
// Struct fields must always be populated
EXPECT_EQ(static_cast<int>(res.x.size()), n);
EXPECT_GE(res.iterations, 0);
EXPECT_FALSE(std::isnan(res.grad_inf_norm));
EXPECT_FALSE(std::isinf(res.grad_inf_norm));
}
// ════════════════════════════════════════════════════════════════════════════
// SparseQR fallback — Test 12: solve_linear_system recovers correct solution
//
// The public API solve_linear_system(A, rhs) must return the correct answer
// for a well-conditioned full-rank system (LDLT path taken).
// ════════════════════════════════════════════════════════════════════════════
TEST(SparseQRFallback, FullRankSystem_CorrectSolution)
{
// Build a simple 3×3 diagonal PD matrix: A = diag(1, 2, 3)
Eigen::SparseMatrix<double> A(3, 3);
A.insert(0, 0) = 1.0;
A.insert(1, 1) = 2.0;
A.insert(2, 2) = 3.0;
A.makeCompressed();
Eigen::VectorXd rhs(3);
rhs << 1.0, 4.0, 9.0; // solution = [1, 2, 3]
bool fallback = true; // expect it to be set to false (LDLT succeeds)
Eigen::VectorXd x = conformallab::solve_linear_system(A, rhs, &fallback);
EXPECT_FALSE(fallback) << "Full-rank system: LDLT should succeed (no SparseQR needed)";
EXPECT_NEAR(x[0], 1.0, 1e-12);
EXPECT_NEAR(x[1], 2.0, 1e-12);
EXPECT_NEAR(x[2], 3.0, 1e-12);
}
// ════════════════════════════════════════════════════════════════════════════
// SparseQR fallback — Test 13: fallback_used=true on a singular matrix
//
// Construct a symmetric 3×3 matrix of rank 1 where LDLT fails (the (2,2)
// pivot is zero). SparseQR finds the minimum-norm least-squares solution.
// ════════════════════════════════════════════════════════════════════════════
TEST(SparseQRFallback, SingularMatrix_FallbackActivated)
{
// A = [[2, 0, 0],
// [0, 0, 0], ← zero pivot → LDLT failure
// [0, 0, 3]]
// rhs compatible with the row space: [2, 0, 3] → solution [1, 0, 1]
Eigen::SparseMatrix<double> A(3, 3);
A.insert(0, 0) = 2.0;
// row/col 1 deliberately all-zero
A.insert(2, 2) = 3.0;
A.makeCompressed();
Eigen::VectorXd rhs(3);
rhs << 2.0, 0.0, 3.0;
bool fallback = false;
Eigen::VectorXd x = conformallab::solve_linear_system(A, rhs, &fallback);
EXPECT_TRUE(fallback) << "Singular matrix: SparseQR fallback must be triggered";
// SparseQR min-norm solution: x[0]=1, x[1]=0, x[2]=1
EXPECT_NEAR(x[0], 1.0, 1e-10);
EXPECT_NEAR(x[1], 0.0, 1e-10);
EXPECT_NEAR(x[2], 1.0, 1e-10);
}
// ════════════════════════════════════════════════════════════════════════════
// SparseQR fallback — Test 14: Euclidean Newton on a closed mesh, no pinning
//
// make_tetrahedron() is a closed surface (4 vertices, 4 faces). Without a
// pinned vertex the Euclidean Hessian has a 1-D null space (uniform scale
// gauge mode): H·1 = 0. SimplicialLDLT fails on this rank-deficient H;
// SparseQR finds the min-norm Newton step orthogonal to the null space.
//
// The gradient always lives in the row space of H (Σ G_v = 0 by angle-sum
// invariance), so the SparseQR step is also the Newton step and the solver
// converges to the natural equilibrium.
// ════════════════════════════════════════════════════════════════════════════
TEST(SparseQRFallback, Euclidean_ClosedMeshNoPinConverges)
{
auto mesh = make_tetrahedron();
auto maps = setup_euclidean_maps(mesh);
compute_euclidean_lambda0_from_mesh(mesh, maps);
// Assign all 4 vertices as free DOFs (no pinning).
int idx = 0;
for (auto v : mesh.vertices())
maps.v_idx[v] = idx++;
const int n = idx; // = 4
// Natural theta: equilibrium at x* = 0.
set_natural_euclidean_theta(mesh, maps, n);
std::vector<double> x0(static_cast<std::size_t>(n), -0.1);
auto res = newton_euclidean(mesh, x0, maps, /*tol=*/1e-8, /*max_iter=*/100);
EXPECT_TRUE(res.converged)
<< "Euclidean Newton on closed tetrahedron (no pin) must converge via SparseQR; "
"grad_inf_norm = " << res.grad_inf_norm;
EXPECT_LT(res.grad_inf_norm, 1e-8);
}

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@@ -0,0 +1,292 @@
// test_pipeline.cpp
//
// Phase 4c — End-to-end pipeline tests and library-user examples.
//
// These tests exercise the full conformallab++ pipeline as a user would:
//
// 1. Build (or load) a mesh
// 2. Set up maps and assign DOFs
// 3. Configure target angles / targets
// 4. Solve with Newton
// 5. Inspect / export the result
//
// Each test mirrors a realistic usage scenario documented in the README.
//
// Tests:
// 1. Pipeline_Euclidean_TriangleToEquilibrium
// Read mesh → setup Euclidean maps → solve → verify convergence
// 2. Pipeline_Spherical_TetrahedronToEquilibrium
// Setup spherical tetrahedron → solve → verify angles sum to 4π
// 3. Pipeline_HyperIdeal_TriangleRoundTrip
// Build triangle → setup HyperIdeal → solve → verify G ≈ 0
// 4. Pipeline_MeshIO_SolveAndExport
// Build mesh → solve → write OFF → reload → verify vertex count intact
// 5. Pipeline_AllThreeGeometries_SameTopology
// Same quad-strip mesh solved under all three geometries: all converge
#include "conformal_mesh.hpp"
#include "mesh_builder.hpp"
#include "mesh_io.hpp"
#include "euclidean_functional.hpp"
#include "spherical_functional.hpp"
#include "hyper_ideal_functional.hpp"
#include "newton_solver.hpp"
#include <gtest/gtest.h>
#include <cmath>
#include <vector>
#include <filesystem>
using namespace conformallab;
// ────────────────────────────────────────────────────────────────────────────
// Shared helpers
// ────────────────────────────────────────────────────────────────────────────
static void pin_first_vertex_euclidean(ConformalMesh& mesh, EuclideanMaps& maps, int& n)
{
auto vit = mesh.vertices().begin();
Vertex_index v0 = *vit++;
maps.v_idx[v0] = -1;
int idx = 0;
for (; vit != mesh.vertices().end(); ++vit)
maps.v_idx[*vit] = idx++;
n = idx;
}
static void set_natural_euclidean_theta(ConformalMesh& mesh, EuclideanMaps& maps, int n)
{
std::vector<double> x0(static_cast<std::size_t>(n), 0.0);
auto G = euclidean_gradient(mesh, x0, maps);
for (auto v : mesh.vertices()) {
int iv = maps.v_idx[v];
if (iv < 0) continue;
maps.theta_v[v] -= G[static_cast<std::size_t>(iv)];
}
}
static std::vector<double> set_natural_hyper_ideal_targets(
ConformalMesh& mesh, HyperIdealMaps& maps, int n,
double b_base = 1.0, double a_base = 0.5)
{
const auto sz = static_cast<std::size_t>(n);
std::vector<double> xbase(sz, 0.0);
for (auto v : mesh.vertices()) {
int iv = maps.v_idx[v];
if (iv >= 0) xbase[static_cast<std::size_t>(iv)] = b_base;
}
for (auto e : mesh.edges()) {
int ie = maps.e_idx[e];
if (ie >= 0) xbase[static_cast<std::size_t>(ie)] = a_base;
}
auto G = evaluate_hyper_ideal(mesh, xbase, maps, false).gradient;
for (auto v : mesh.vertices()) {
int iv = maps.v_idx[v];
if (iv < 0) continue;
maps.theta_v[v] += G[static_cast<std::size_t>(iv)];
}
for (auto e : mesh.edges()) {
int ie = maps.e_idx[e];
if (ie < 0) continue;
maps.theta_e[e] += G[static_cast<std::size_t>(ie)];
}
return xbase;
}
// ════════════════════════════════════════════════════════════════════════════
// Test 1 — Euclidean full pipeline: triangle → equilibrium
//
// Simulates a user doing:
// auto mesh = make_triangle();
// auto maps = setup_euclidean_maps(mesh);
// compute_euclidean_lambda0_from_mesh(mesh, maps);
// // … set target angles and DOF indices …
// auto result = newton_euclidean(mesh, x0, maps);
// assert(result.converged);
// ════════════════════════════════════════════════════════════════════════════
TEST(Pipeline, Euclidean_TriangleToEquilibrium)
{
// ── Step 1: build mesh ────────────────────────────────────────────────
auto mesh = make_triangle();
// ── Step 2: set up maps ───────────────────────────────────────────────
auto maps = setup_euclidean_maps(mesh);
compute_euclidean_lambda0_from_mesh(mesh, maps);
// ── Step 3: assign DOFs (pin v0) ──────────────────────────────────────
int n = 0;
pin_first_vertex_euclidean(mesh, maps, n);
ASSERT_EQ(n, 2);
// ── Step 4: choose natural target angles → x* = 0 ────────────────────
set_natural_euclidean_theta(mesh, maps, n);
// ── Step 5: solve ─────────────────────────────────────────────────────
std::vector<double> x0(static_cast<std::size_t>(n), -0.1);
auto result = newton_euclidean(mesh, x0, maps);
// ── Step 6: verify ────────────────────────────────────────────────────
EXPECT_TRUE(result.converged)
<< "Euclidean pipeline: triangle should converge; "
"grad_inf_norm = " << result.grad_inf_norm;
EXPECT_LT(result.grad_inf_norm, 1e-8);
EXPECT_EQ(static_cast<int>(result.x.size()), n);
}
// ════════════════════════════════════════════════════════════════════════════
// Test 2 — Spherical full pipeline: tetrahedron → equilibrium
//
// The spherical tetrahedron equilibrium x* = 0 is built into the maps.
// After solving, the total angle defect Σ(Θ_v Σα_v) should be ≈ 0.
// ════════════════════════════════════════════════════════════════════════════
TEST(Pipeline, Spherical_TetrahedronToEquilibrium)
{
// ── Steps 13 ─────────────────────────────────────────────────────────
auto mesh = make_spherical_tetrahedron();
auto maps = setup_spherical_maps(mesh);
compute_lambda0_from_mesh(mesh, maps);
int n = assign_vertex_dof_indices(mesh, maps);
// ── Step 4: solve ─────────────────────────────────────────────────────
std::vector<double> x0(static_cast<std::size_t>(n), -0.2);
auto result = newton_spherical(mesh, x0, maps);
// ── Step 5: verify convergence ────────────────────────────────────────
EXPECT_TRUE(result.converged)
<< "Spherical pipeline: tetrahedron should converge; "
"grad_inf_norm = " << result.grad_inf_norm;
EXPECT_LT(result.grad_inf_norm, 1e-8);
// ── Step 6: verify geometric invariant — total angle defect ≈ 0 ──────
auto G_final = spherical_gradient(mesh, result.x, maps);
double total_defect = 0.0;
for (double gv : G_final) total_defect += gv;
EXPECT_NEAR(total_defect, 0.0, 1e-7)
<< "Spherical: total angle defect should vanish at equilibrium";
}
// ════════════════════════════════════════════════════════════════════════════
// Test 3 — HyperIdeal full pipeline: triangle → equilibrium
// ════════════════════════════════════════════════════════════════════════════
TEST(Pipeline, HyperIdeal_TriangleRoundTrip)
{
// ── Steps 13 ─────────────────────────────────────────────────────────
auto mesh = make_triangle();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
// ── Step 4: natural targets (equilibrium at b=1.0, a=0.5) ────────────
auto xbase = set_natural_hyper_ideal_targets(mesh, maps, n);
// Verify: gradient at xbase must be ≈ 0 before solving
auto G_at_base = evaluate_hyper_ideal(mesh, xbase, maps, false).gradient;
double max_g = 0.0;
for (double v : G_at_base) max_g = std::max(max_g, std::abs(v));
ASSERT_LT(max_g, 1e-10) << "Natural target setup: gradient at base should be ~0";
// ── Step 5: perturb and solve ─────────────────────────────────────────
std::vector<double> x0 = xbase;
for (auto& v : x0) v += 0.3;
auto result = newton_hyper_ideal(mesh, x0, maps);
// ── Step 6: verify ────────────────────────────────────────────────────
EXPECT_TRUE(result.converged)
<< "HyperIdeal pipeline: triangle should converge; "
"grad_inf_norm = " << result.grad_inf_norm;
EXPECT_LT(result.grad_inf_norm, 1e-8);
// Solution should be close to xbase (same equilibrium)
for (int i = 0; i < n; ++i) {
EXPECT_NEAR(result.x[static_cast<std::size_t>(i)],
xbase[static_cast<std::size_t>(i)], 1e-6)
<< "DOF " << i << " should recover the equilibrium value";
}
}
// ════════════════════════════════════════════════════════════════════════════
// Test 4 — Mesh I/O in the pipeline: solve → write → reload → check
//
// Demonstrates: compute a conformal factor on a mesh, write it to OFF, reload
// and check that the mesh topology is preserved.
// ════════════════════════════════════════════════════════════════════════════
TEST(Pipeline, MeshIO_SolveAndExport)
{
// ── Build and solve ───────────────────────────────────────────────────
auto mesh = make_quad_strip();
auto maps = setup_euclidean_maps(mesh);
compute_euclidean_lambda0_from_mesh(mesh, maps);
int n = 0;
pin_first_vertex_euclidean(mesh, maps, n);
set_natural_euclidean_theta(mesh, maps, n);
std::vector<double> x0(static_cast<std::size_t>(n), -0.1);
auto result = newton_euclidean(mesh, x0, maps);
ASSERT_TRUE(result.converged) << "Solver must converge before export test";
// ── Write mesh ────────────────────────────────────────────────────────
const std::string tmp_path = "/tmp/conformallab_pipeline_test.off";
ASSERT_NO_THROW(save_mesh(tmp_path, mesh));
ASSERT_TRUE(std::filesystem::exists(tmp_path));
// ── Reload and verify topology ────────────────────────────────────────
ConformalMesh mesh2;
ASSERT_NO_THROW(mesh2 = load_mesh(tmp_path));
EXPECT_EQ(mesh2.number_of_vertices(), mesh.number_of_vertices())
<< "Vertex count must survive OFF round-trip";
EXPECT_EQ(mesh2.number_of_faces(), mesh.number_of_faces())
<< "Face count must survive OFF round-trip";
std::filesystem::remove(tmp_path);
}
// ════════════════════════════════════════════════════════════════════════════
// Test 5 — All three geometries, same quad-strip topology
//
// Validates that the solver infrastructure works uniformly: the same mesh
// topology is solvable under Euclidean, Spherical, and HyperIdeal geometries.
// ════════════════════════════════════════════════════════════════════════════
TEST(Pipeline, AllThreeGeometries_QuadStrip)
{
// ── Euclidean ──────────────────────────────────────────────────────────
{
auto mesh = make_quad_strip();
auto maps = setup_euclidean_maps(mesh);
compute_euclidean_lambda0_from_mesh(mesh, maps);
int n = 0;
pin_first_vertex_euclidean(mesh, maps, n);
set_natural_euclidean_theta(mesh, maps, n);
std::vector<double> x0(static_cast<std::size_t>(n), -0.1);
auto res = newton_euclidean(mesh, x0, maps);
EXPECT_TRUE(res.converged) << "Euclidean: quad strip should converge";
}
// ── HyperIdeal ────────────────────────────────────────────────────────
{
auto mesh = make_quad_strip();
auto maps = setup_hyper_ideal_maps(mesh);
int n = assign_all_dof_indices(mesh, maps);
auto xbase = set_natural_hyper_ideal_targets(mesh, maps, n);
std::vector<double> x0 = xbase;
for (auto& v : x0) v += 0.1;
auto res = newton_hyper_ideal(mesh, x0, maps);
EXPECT_TRUE(res.converged) << "HyperIdeal: quad strip should converge";
}
// ── Spherical (tetrahedron: smallest closed mesh with all vertices free) ─
{
auto mesh = make_spherical_tetrahedron();
auto maps = setup_spherical_maps(mesh);
compute_lambda0_from_mesh(mesh, maps);
int n = assign_vertex_dof_indices(mesh, maps);
std::vector<double> x0(static_cast<std::size_t>(n), -0.1);
auto res = newton_spherical(mesh, x0, maps);
EXPECT_TRUE(res.converged) << "Spherical: tetrahedron should converge";
}
}