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FESADev/tests/unit/analysis/hht_temporal_verification_test.cpp
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2026-09-22 21:38:42 +09:00

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#include <gtest/gtest.h>
#include <algorithm>
#include <array>
#include <cmath>
#include <cstddef>
#include <iostream>
#include <limits>
#include <stdexcept>
#include <vector>
#include "fesa/analysis/hht_time_integration.h"
namespace {
enum class Case { kC01, kC03, kC04a, kC04b };
using Dense = std::array<std::array<double, 2>, 2>;
struct ExactState {
fesa::Vector q;
fesa::Vector v;
fesa::Vector a;
};
std::size_t Dimension(const Case model) {
return model == Case::kC01 || model == Case::kC03 ? 1U : 2U;
}
ExactState Exact(const Case model, const double time) {
const std::size_t size = Dimension(model);
ExactState result{fesa::Vector{size}, fesa::Vector{size}, fesa::Vector{size}};
if (model == Case::kC01) {
result.q[0] = std::cos(2.0 * time) + 0.15 * std::sin(2.0 * time);
result.v[0] = -2.0 * std::sin(2.0 * time) + 0.3 * std::cos(2.0 * time);
result.a[0] = -4.0 * result.q[0];
} else if (model == Case::kC03) {
result.q[0] = 0.4 + std::sin(time);
result.v[0] = std::cos(time);
result.a[0] = -std::sin(time);
} else if (model == Case::kC04a) {
result.q[0] = 0.25 * (1.0 - std::cos(2.0 * time));
result.v[0] = 0.5 * std::sin(2.0 * time);
result.a[0] = std::cos(2.0 * time);
result.q[1] = 0.7 * result.q[0];
result.v[1] = 0.7 * result.v[0];
result.a[1] = 0.7 * result.a[0];
} else {
result.q[0] = std::cos(time);
result.q[1] = std::sin(time);
result.v[0] = -std::sin(time);
result.v[1] = std::cos(time);
result.a[0] = -result.q[0];
result.a[1] = -result.q[1];
}
return result;
}
std::array<double, 3> Amplitudes(const Case model) {
if (model == Case::kC01) {
const double q = std::sqrt(1.0 + 0.15 * 0.15);
return {q, 2.0 * q, 4.0 * q};
}
if (model == Case::kC04a) {
const double direction = std::sqrt(1.0 + 0.7 * 0.7);
return {0.5 * direction, 0.5 * direction, direction};
}
return {1.0, 1.0, 1.0};
}
struct Equation {
Dense mass{};
Dense dq{};
Dense dv{};
fesa::Vector residual;
fesa::Vector scale;
};
Equation Evaluate(const Case model, const fesa::Vector& q,
const fesa::Vector& v, const fesa::Vector& a,
const double time) {
const std::size_t size = q.Size();
Equation result{{}, {}, {}, fesa::Vector{size}, fesa::Vector{size}};
fesa::Vector c{size};
fesa::Vector internal{size};
fesa::Vector force{size};
if (model == Case::kC01) {
result.mass[0][0] = 1.0;
result.dq[0][0] = 4.0;
internal[0] = 4.0 * q[0];
} else if (model == Case::kC03) {
result.mass[0][0] = 1.0 + q[0] * q[0];
c[0] = q[0] * v[0] * v[0];
const auto exact = Exact(model, time);
force[0] = (1.0 + exact.q[0] * exact.q[0]) * exact.a[0] +
exact.q[0] * exact.v[0] * exact.v[0];
result.dq[0][0] = 2.0 * q[0] * a[0] + v[0] * v[0];
result.dv[0][0] = 2.0 * q[0] * v[0];
} else if (model == Case::kC04a) {
result.mass[0][0] = 2.0;
result.dq = {{{8.0 + 3.0 * 0.7 * 0.7, -3.0 * 0.7}, {-3.0 * 0.7, 3.0}}};
internal[0] = result.dq[0][0] * q[0] + result.dq[0][1] * q[1];
internal[1] = result.dq[1][0] * q[0] + result.dq[1][1] * q[1];
force[0] = 2.0;
} else {
const double radius = q.Norm();
if (!(radius > 0.0)) throw std::runtime_error{"Invalid circle chart."};
const double r2 = radius * radius;
const double r4 = r2 * r2;
const double r6 = r4 * r2;
const double s = q.Dot(v);
std::array<double, 2> mv{};
for (std::size_t i = 0; i < 2; ++i) {
for (std::size_t j = 0; j < 2; ++j) {
result.mass[i][j] = (i == j ? 1.0 / r2 : 0.0) - q[i] * q[j] / r4;
mv[i] += result.mass[i][j] * v[j];
}
c[i] = -2.0 * s / r2 * mv[i];
internal[i] = (1.0 - 1.0 / radius) * q[i];
}
for (std::size_t column = 0; column < 2; ++column) {
for (std::size_t row = 0; row < 2; ++row) {
double dma = 0.0;
double dmv = 0.0;
for (std::size_t j = 0; j < 2; ++j) {
const double derivative =
(row == j ? -2.0 * q[column] / r4 : 0.0) +
4.0 * q[column] * q[row] * q[j] / r6 -
((row == column ? q[j] : 0.0) + (j == column ? q[row] : 0.0)) /
r4;
dma += derivative * a[j];
dmv += derivative * v[j];
}
result.dq[row][column] =
dma + (-2.0 * v[column] / r2 + 4.0 * s * q[column] / r4) * mv[row] -
2.0 * s / r2 * dmv + (row == column ? 1.0 - 1.0 / radius : 0.0) +
q[row] * q[column] / (r2 * radius);
result.dv[row][column] = -2.0 * q[column] / r2 * mv[row] -
2.0 * s / r2 * result.mass[row][column];
}
}
}
for (std::size_t i = 0; i < size; ++i) {
result.residual[i] = c[i] + internal[i] - force[i];
result.scale[i] =
std::abs(c[i]) + std::abs(internal[i]) + std::abs(force[i]);
for (std::size_t j = 0; j < size; ++j) {
result.residual[i] += result.mass[i][j] * a[j];
result.scale[i] += std::abs(result.mass[i][j] * a[j]);
}
}
return result;
}
fesa::Vector Multiply(const Dense& matrix, const fesa::Vector& x) {
fesa::Vector result{x.Size()};
for (std::size_t i = 0; i < x.Size(); ++i) {
for (std::size_t j = 0; j < x.Size(); ++j) result[i] += matrix[i][j] * x[j];
}
return result;
}
fesa::Vector Solve(const Dense& matrix, const fesa::Vector& rhs) {
fesa::Vector result{rhs.Size()};
if (rhs.Size() == 1U) {
if (matrix[0][0] == 0.0)
throw std::runtime_error{"Singular scalar tangent."};
result[0] = rhs[0] / matrix[0][0];
} else {
Dense lu = matrix;
std::array<double, 2> b{rhs[0], rhs[1]};
if (std::abs(lu[1][0]) > std::abs(lu[0][0])) {
std::swap(lu[0], lu[1]);
std::swap(b[0], b[1]);
}
if (lu[0][0] == 0.0) throw std::runtime_error{"Singular Cartesian pivot."};
const double multiplier = lu[1][0] / lu[0][0];
lu[1][1] -= multiplier * lu[0][1];
b[1] -= multiplier * b[0];
if (lu[1][1] == 0.0) throw std::runtime_error{"Singular Cartesian pivot."};
result[1] = b[1] / lu[1][1];
result[0] = (b[0] - lu[0][1] * result[1]) / lu[0][0];
}
double residual_norm = 0.0;
double scale_norm = 0.0;
for (std::size_t i = 0; i < rhs.Size(); ++i) {
double residual = -rhs[i];
double scale = std::abs(rhs[i]);
for (std::size_t j = 0; j < rhs.Size(); ++j) {
residual += matrix[i][j] * result[j];
scale += std::abs(matrix[i][j] * result[j]);
}
EXPECT_TRUE(std::isfinite(result[i]));
residual_norm = std::max(residual_norm, std::abs(residual));
scale_norm = std::max(scale_norm, scale);
}
EXPECT_LE(scale_norm > 0.0 ? residual_norm / scale_norm : residual_norm,
1.0e-12);
return result;
}
Dense Effective(const Equation& equation, const double cv, const double ca) {
Dense tangent{};
for (std::size_t i = 0; i < 2; ++i) {
for (std::size_t j = 0; j < 2; ++j) {
tangent[i][j] =
equation.dq[i][j] + cv * equation.dv[i][j] + ca * equation.mass[i][j];
}
}
return tangent;
}
struct Errors {
std::array<double, 3> maximum{};
std::array<double, 3> first{};
std::array<double, 3> tail{};
std::array<double, 3> endpoint{};
std::array<double, 3> noise{};
double position_constraint = 0.0;
double hidden_velocity = 0.0;
double hidden_acceleration = 0.0;
double auxiliary_difference = 0.0;
double constant_mass_recurrence_difference = 0.0;
double reduced_difference = 0.0;
};
Errors Integrate(const Case model, const std::size_t increments,
const bool naive_variable_mass = false) {
const double h = 1.0 / static_cast<double>(increments);
const auto parameter_result = fesa::MakeHhtParameters(-0.05);
if (!parameter_result.HasValue())
throw std::runtime_error{"Invalid HHT parameters."};
const auto parameters = parameter_result.Value();
const double cv = parameters.gamma / (parameters.beta * h);
const double ca = 1.0 / ((1.0 + parameters.alpha) * parameters.beta * h * h);
ExactState state = Exact(model, 0.0);
fesa::Vector auxiliary = state.a;
const auto amplitudes = Amplitudes(model);
Errors errors;
double old_naive_b = 0.0;
double old_naive_scale = 2.0 * std::abs(state.q[0] * state.v[0] * state.v[0]);
if (naive_variable_mass)
old_naive_b = -(1.0 + state.q[0] * state.q[0]) * state.a[0];
// Independent scalar constant-M HHT recurrence, used for C01 and the exact
// algebraic reduction of C04a; it does not call the production rate helpers.
double rq = state.q[0];
double rv = state.v[0];
double ra = state.a[0];
for (std::size_t step = 1; step <= increments; ++step) {
const double time = static_cast<double>(step) * h;
const auto predictor_result =
fesa::PredictHht(state.q, state.v, auxiliary, h, parameters);
if (!predictor_result.HasValue())
throw std::runtime_error{"Invalid predictor."};
const auto predictor = predictor_result.Value();
fesa::Vector q = predictor.coordinates;
q.Axpy(parameters.beta * h * h, auxiliary);
fesa::Vector last_delta{q.Size()};
fesa::Vector last_residual{q.Size()};
Dense last_tangent{};
std::size_t corrections = 0U;
for (;;) {
const auto rates =
fesa::EvaluateHhtRates(q, predictor, state.a, h, parameters);
if (!rates.HasValue()) throw std::runtime_error{"Invalid trial rates."};
auto equation = Evaluate(model, q, rates.Value().velocity,
rates.Value().acceleration, time);
Dense tangent = Effective(equation, cv, ca);
if (naive_variable_mass) {
const auto exact = Exact(model, time);
const double force = (1.0 + exact.q[0] * exact.q[0]) * exact.a[0] +
exact.q[0] * exact.v[0] * exact.v[0];
const double v = rates.Value().velocity[0];
const double a = rates.Value().algorithmic_acceleration[0];
const double b = q[0] * v * v - force;
equation.residual[0] = (1.0 + q[0] * q[0]) * a +
(1.0 + parameters.alpha) * b -
parameters.alpha * old_naive_b;
equation.scale[0] = std::abs((1.0 + q[0] * q[0]) * a) +
(1.0 + parameters.alpha) *
(std::abs(q[0] * v * v) + std::abs(force)) +
std::abs(parameters.alpha) * old_naive_scale;
tangent[0][0] =
2.0 * q[0] * a + (1.0 + q[0] * q[0]) / (parameters.beta * h * h) +
(1.0 + parameters.alpha) * (v * v + 2.0 * q[0] * v * cv);
}
double residual = 0.0;
double scale = 0.0;
double correction = 0.0;
for (std::size_t i = 0; i < q.Size(); ++i) {
residual = std::max(residual, std::abs(equation.residual[i]));
scale = std::max(scale, equation.scale[i]);
correction = std::max(correction, std::abs(last_delta[i]));
}
const bool force_pass =
scale > 0.0 ? residual / scale <= 1.0e-10 : residual == 0.0;
const bool correction_pass = correction <= 1.0e-10 &&
h * cv * correction <= 1.0e-10 &&
h * h * ca * correction <= 1.0e-10 &&
correction / parameters.beta <= 1.0e-10;
if (force_pass && correction_pass) {
if (corrections == 0U) {
last_tangent = tangent;
last_residual = equation.residual;
}
break;
}
if (corrections >= 100U)
throw std::runtime_error{"Newton correction limit."};
auto rhs = equation.residual;
rhs.Scale(-1.0);
last_delta = Solve(tangent, rhs);
last_tangent = tangent;
last_residual = equation.residual;
q.Axpy(1.0, last_delta);
++corrections;
}
const auto rates_result =
fesa::EvaluateHhtRates(q, predictor, state.a, h, parameters);
if (!rates_result.HasValue())
throw std::runtime_error{"Invalid accepted rates."};
const auto rates = rates_result.Value();
const auto endpoint_equation =
Evaluate(model, q, rates.velocity, rates.acceleration, time);
const Dense endpoint_tangent = Effective(endpoint_equation, cv, ca);
if (!naive_variable_mass) {
auto linear_defect = Multiply(last_tangent, last_delta);
linear_defect.Axpy(1.0, last_residual);
linear_defect.Scale(-1.0);
const auto z_linear = Solve(last_tangent, linear_defect);
auto endpoint_rhs = endpoint_equation.residual;
endpoint_rhs.Scale(-1.0);
const auto z_nonlinear = Solve(endpoint_tangent, endpoint_rhs);
const double eta_q =
last_delta.Norm() + z_linear.Norm() + z_nonlinear.Norm();
const double unit_roundoff = std::ldexp(1.0, -53);
const double gamma32 =
32.0 * unit_roundoff / (1.0 - 32.0 * unit_roundoff);
const double eta_round =
gamma32 * (q.Norm() + predictor.coordinates.Norm());
const std::array<double, 3> factors{1.0, cv, ca};
for (std::size_t channel = 0; channel < 3; ++channel) {
errors.noise[channel] =
std::max(errors.noise[channel], factors[channel] *
std::max(eta_q, eta_round) /
amplitudes[channel]);
}
}
const auto exact = Exact(model, time);
const std::array<const fesa::Vector*, 3> actual{&q, &rates.velocity,
&rates.acceleration};
const std::array<const fesa::Vector*, 3> reference{&exact.q, &exact.v,
&exact.a};
for (std::size_t channel = 0; channel < 3; ++channel) {
auto difference = *actual[channel];
difference.Axpy(-1.0, *reference[channel]);
const double error = difference.Norm() / amplitudes[channel];
errors.maximum[channel] = std::max(errors.maximum[channel], error);
if (step == 1U) errors.first[channel] = error;
if (time >= 0.25)
errors.tail[channel] = std::max(errors.tail[channel], error);
if (step == increments) errors.endpoint[channel] = error;
}
auto auxiliary_difference = rates.algorithmic_acceleration;
auxiliary_difference.Axpy(-1.0, rates.acceleration);
errors.auxiliary_difference =
std::max(errors.auxiliary_difference, auxiliary_difference.Norm());
if (model == Case::kC04b) {
errors.position_constraint =
std::max(errors.position_constraint, std::abs(q.Norm() - 1.0));
errors.hidden_velocity =
std::max(errors.hidden_velocity, std::abs(q.Dot(rates.velocity)));
errors.hidden_acceleration =
std::max(errors.hidden_acceleration,
std::abs(q.Dot(rates.acceleration) +
rates.velocity.Dot(rates.velocity)));
}
if (model == Case::kC01 || model == Case::kC04a) {
const double m = model == Case::kC01 ? 1.0 : 2.0;
const double k = model == Case::kC01 ? 4.0 : 8.0;
const double force = model == Case::kC01 ? 0.0 : 2.0;
const double qp = rq + h * rv + h * h * (0.5 - parameters.beta) * ra;
const double next_a =
((1.0 + parameters.alpha) * (force - k * qp) -
parameters.alpha * (force - k * rq)) /
(m + (1.0 + parameters.alpha) * k * parameters.beta * h * h);
const double next_q = qp + parameters.beta * h * h * next_a;
const double next_v =
rv + h * ((1.0 - parameters.gamma) * ra + parameters.gamma * next_a);
errors.constant_mass_recurrence_difference = std::max(
errors.constant_mass_recurrence_difference,
std::max(std::abs(q[0] - next_q) / amplitudes[0],
std::abs(rates.velocity[0] - next_v) / amplitudes[1]));
if (model == Case::kC04a) {
errors.reduced_difference = std::max(
errors.reduced_difference,
std::max({std::abs(q[1] - 0.7 * q[0]),
std::abs(rates.velocity[1] - 0.7 * rates.velocity[0]),
std::abs(rates.acceleration[1] -
0.7 * rates.acceleration[0])}));
}
rq = next_q;
rv = next_v;
ra = next_a;
}
if (naive_variable_mass) {
const double force = (1.0 + exact.q[0] * exact.q[0]) * exact.a[0] +
exact.q[0] * exact.v[0] * exact.v[0];
old_naive_b = q[0] * rates.velocity[0] * rates.velocity[0] - force;
old_naive_scale = std::abs(q[0] * rates.velocity[0] * rates.velocity[0]) +
std::abs(force);
}
state = {q, rates.velocity, rates.acceleration};
auxiliary = rates.algorithmic_acceleration;
}
return errors;
}
std::vector<Errors> Sweep(const Case model) {
std::vector<Errors> errors;
for (const std::size_t increments : {16U, 32U, 64U, 128U, 256U}) {
errors.push_back(Integrate(model, increments));
const auto& current = errors.back();
for (std::size_t channel = 0; channel < 3; ++channel) {
std::cout << "N7 model=" << static_cast<int>(model)
<< " increments=" << increments << " channel=" << channel
<< " maximum=" << current.maximum[channel]
<< " first=" << current.first[channel]
<< " tail=" << current.tail[channel]
<< " endpoint=" << current.endpoint[channel]
<< " noise=" << current.noise[channel] << '\n';
EXPECT_GT(current.maximum[channel], 100.0 * current.noise[channel])
<< "N7 inconclusive: iteration/roundoff dominates channel "
<< channel;
}
std::cout << "N7 hidden v=" << current.hidden_velocity
<< " a=" << current.hidden_acceleration
<< " A-a=" << current.auxiliary_difference << '\n';
}
for (std::size_t channel = 0; channel < 3; ++channel) {
for (std::size_t grid = 3; grid < 5; ++grid) {
EXPECT_LT(errors[grid].maximum[channel],
errors[grid - 1U].maximum[channel]);
EXPECT_GE(std::log2(errors[grid - 1U].maximum[channel] /
errors[grid].maximum[channel]),
1.8);
}
EXPECT_LE(errors.back().maximum[channel], 1.0e-4);
}
return errors;
}
TEST(HhtTemporalVerification, C01MatchesConstantMassRecurrenceAndSecondOrder) {
const auto errors = Sweep(Case::kC01);
for (const auto& error : errors)
EXPECT_LE(error.constant_mass_recurrence_difference, 1.0e-12);
}
TEST(HhtTemporalVerification,
C03VariableMassIsSecondOrderAndNaiveWeightingIsNot) {
const auto errors = Sweep(Case::kC03);
EXPECT_GT(errors.back().auxiliary_difference, 0.0);
const auto coarse = Integrate(Case::kC03, 128U, true);
const auto fine = Integrate(Case::kC03, 256U, true);
const double order = std::log2(coarse.maximum[0] / fine.maximum[0]);
std::cout << "C03 naive q-order=" << order << '\n';
EXPECT_LT(order, 1.5);
}
TEST(HhtTemporalVerification, C04aCoupledMasslessCoordinatesHaveSecondOrder) {
const auto errors = Sweep(Case::kC04a);
for (std::size_t grid = 0; grid < errors.size(); ++grid) {
EXPECT_LE(errors[grid].constant_mass_recurrence_difference, 1.0e-12);
if (grid + 1U < errors.size())
EXPECT_LE(errors[grid].reduced_difference, 1.0e-10);
}
}
TEST(HhtTemporalVerification,
C04aFinestReductionComparisonIsNumericallyResolved) {
const auto error = Integrate(Case::kC04a, 256U);
if (error.reduced_difference > 1.0e-10 &&
error.reduced_difference <= error.noise[2]) {
GTEST_SKIP() << "N7 INCONCLUSIVE: h=1/256 full/reduced acceleration defect="
<< error.reduced_difference
<< ", arithmetic/solve resolution=" << error.noise[2]
<< "; coarse grids remain blocking. Independent decimal80 "
"full2x2/reduced"
" recurrence evidence is recorded separately; this "
"binary64 comparison is not passed.";
}
EXPECT_LE(error.reduced_difference, 1.0e-10);
}
TEST(HhtTemporalVerification, C04bFullCartesianMovingNullConverges) {
const auto errors = Sweep(Case::kC04b);
for (const auto& error : errors)
EXPECT_LE(error.position_constraint, 1.0e-10);
for (std::size_t grid = 3; grid < 5; ++grid) {
EXPECT_LT(errors[grid].hidden_velocity, errors[grid - 1U].hidden_velocity);
EXPECT_LT(errors[grid].hidden_acceleration,
errors[grid - 1U].hidden_acceleration);
}
EXPECT_LE(errors.back().hidden_velocity, 1.0e-6);
EXPECT_LE(errors.back().hidden_acceleration, 1.0e-4);
}
} // namespace