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test_kepler.cc
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Wed, Nov 6, 07:20

test_kepler.cc
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#include "compute_gravity.hh"
#include "compute_verlet_integration.hh"
#include "csv_reader.hh"
#include "csv_writer.hh"
#include "planet.hh"
#include "planets_factory.hh"
#include "system.hh"
#include <gtest/gtest.h>
/*****************************************************************/
// Fixture class
class RandomPlanets : public ::testing::Test {
protected:
void SetUp() override {
PlanetsFactory::getInstance();
std::vector<Planet> planets;
n_planets = 10;
for (UInt i = 0; i < n_planets; ++i) {
Planet p;
p.getPosition() = 1.;
p.getMass() = 1.;
planets.push_back(p);
}
for (auto& p : planets) {
// std::cout << p << std::endl;
system.addParticle(std::make_shared<Planet>(p));
}
}
System system;
UInt n_planets;
};
/*****************************************************************/
TEST_F(RandomPlanets, csv) {
CsvWriter writer("tmp_file");
writer.compute(system);
CsvReader reader("tmp_file");
System s_fromfile;
reader.compute(s_fromfile);
UInt read_n_planets = s_fromfile.getNbParticles();
EXPECT_EQ(n_planets, s_fromfile.getNbParticles());
for (UInt i = 0; i < n_planets; ++i) {
auto& part1 = system.getParticle(i);
auto& pos1 = part1.getPosition();
auto& part2 = s_fromfile.getParticle(i);
auto& pos2 = part2.getPosition();
for (UInt j = 0; j < 3; ++j) {
ASSERT_NEAR(pos1[j], pos2[j], std::abs(pos1[j]) * 1e-12);
}
}
}
/*****************************************************************/
// Fixture class
class TwoPlanets : public ::testing::Test {
protected:
void SetUp() override {
Planet p1, p2;
p1.getMass() = 1.;
p2.getMass() = 1.;
p1.getPosition() = 0.;
p2.getPosition() = 0.;
p1.getVelocity() = 0.;
p2.getVelocity() = 0.;
system.addParticle(std::make_shared<Planet>(p1));
system.addParticle(std::make_shared<Planet>(p2));
n_planets = 2;
gravity = std::make_shared<ComputeGravity>();
verlet = std::make_shared<ComputeVerletIntegration>(1.);
verlet->addInteraction(this->gravity);
}
System system;
UInt n_planets;
std::shared_ptr<ComputeGravity> gravity;
std::shared_ptr<ComputeVerletIntegration> verlet;
};
/*****************************************************************/
TEST_F(TwoPlanets, gravity_force) {
auto& p1 = system.getParticle(0);
auto& p2 = system.getParticle(1);
p2.getVelocity()[1] = 1.2;
p2.getPosition()[0] = 1.;
gravity->setG(1.);
gravity->compute(system);
ASSERT_NEAR(p1.getForce()[0], 1, 1e-15);
ASSERT_NEAR(p2.getForce()[0], -1, 1e-15);
ASSERT_NEAR(p1.getForce()[1], 0., 1e-15);
ASSERT_NEAR(p2.getForce()[1], 0., 1e-15);
ASSERT_NEAR(p1.getForce()[2], 0., 1e-15);
ASSERT_NEAR(p2.getForce()[2], 0., 1e-15);
}
/*****************************************************************/
TEST_F(TwoPlanets, ellipsoid) {
auto& p1 = system.getParticle(0);
auto& p2 = system.getParticle(1);
verlet->setDeltaT(5e-3);
gravity->setG(1.);
p1.getForce()[1] = 1e-4;
p2.getPosition()[0] = 1.;
p2.getForce()[1] = -1e-4;
p2.getMass() = 1e-4;
p2.getVelocity()[1] = 0.5;
Real min_dist = std::numeric_limits<Real>::max();
Real max_dist = -std::numeric_limits<Real>::max();
for (UInt i = 0; i < 10000; ++i) {
verlet->compute(system);
auto dist = (p2.getPosition() - p1.getPosition()).squaredNorm();
min_dist = std::min(min_dist, dist);
max_dist = std::max(max_dist, dist);
}
Real excentricity = (max_dist - min_dist) / (max_dist + min_dist);
//std::cout << "excentricity:" << excentricity << std::endl;
ASSERT_LT(excentricity, 1.);
}
/*****************************************************************/
TEST_F(TwoPlanets, circular) {
auto& p1 = system.getParticle(0);
auto& p2 = system.getParticle(1);
CsvWriter writer("tmp_file");
writer.compute(system);
verlet->setDeltaT(5e-3);
//verlet->setDeltaT(1e-8);
gravity->setG(1.);
p1.getForce()[1] = 1e-4;
p2.getPosition()[0] = 1.;
p2.getForce()[1] = -1e-4;
p2.getMass() = 1e-4;
p2.getVelocity()[1] = 1.;
for (UInt i = 0; i < 100000; ++i) {
verlet->compute(system);
auto dist = (p2.getPosition() - p1.getPosition()).squaredNorm();
//ASSERT_NEAR(dist, 1., 1e-10);
ASSERT_NEAR(dist, 1., 1e-1);
}
}

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