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Improved initial conditions

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This commit is contained in:
Yohai Meiron 2020-05-07 20:29:41 -04:00
parent d598e739bd
commit ffb74dba6f
1 changed files with 53 additions and 5 deletions
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58
scattering_experiment.cpp
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@ -13,6 +13,9 @@
using double3 = Eigen::Vector3d;
// Our units are {kiloparsec, solar mass, gigayear}
constexpr double G = 4.498317481097514e-06;
extern "C"
void integrate(const double y0[], const double t_max, const double stride_size, double y[]);
@ -81,6 +84,53 @@ private:
double target_d, target_z, target_vd, target_vt, target_vz;
};
class Uniform_sphere_escape_velocity_cutoff {
public:
Uniform_sphere_escape_velocity_cutoff(const double r_max, const double rho_0, const double b)
: r_max(r_max), rho_0(rho_0), b(b)
{
uniform_distribution = std::uniform_real_distribution<double>(0, 1);
}
template<typename Generator>
std::array<double,6> operator()(Generator& generator)
{
std::array<double,6> result;
double r = pow(uniform_distribution(generator), 1./3.)*r_max;
double cos_theta = uniform_distribution(generator)*2-1;
double sin_theta = sqrt(1 - cos_theta*cos_theta);
double phi = uniform_distribution(generator)*2*M_PI;
result[0] = r*cos(phi)*sin_theta;
result[1] = r*sin(phi)*sin_theta;
result[2] = r*cos_theta;
double potential = nfw_potential(r);
if (potential > 0) throw std::runtime_error("Cannot deal with a positive potential");
double v_max = sqrt(-2*potential);
double v_magnitude;
do {
for (int i=3; i<6; i++) result[i] = uniform_distribution(generator);
v_magnitude = sqrt(result[3]*result[3]+result[4]*result[4]+result[5]*result[5]);
} while (v_magnitude >= v_max);
return result;
}
friend std::ostream& operator<<(std::ostream& stream, const Uniform_sphere_escape_velocity_cutoff& obj)
{
stream.setf(std::ios::scientific);
stream << "# Initial conditions type: uniform sphere with escape velocity cutoff\n";
stream << "# Initial conditions parameters:\n";
stream << "# r_max = " << std::setw(13) << obj.r_max << '\n';
}
private:
inline double nfw_potential(double r)
{
return -4*M_PI*G*rho_0*b*b*b*log(1+r/b)/r;
}
double r_max, rho_0, b;
std::uniform_real_distribution<double> uniform_distribution;
};
class Box_initial_conditions {
public:
Box_initial_conditions(double x_max, double v_max)
@ -162,8 +212,6 @@ public:
if (accept(y+6)) {
std::lock_guard<std::mutex> lock(mtx);
char buffer[512];
file << std::setw(3) << tid;
for (int j=0; j<12; j++) file << std::setw(24) << y[j];
file << std::endl;
}
@ -215,10 +263,10 @@ int main()
target_pos *= 0.001; // Now in kpc
target_vel *= 1.0226911647958985; // Now in kpc/Gyr
In_box_cyl accept(2, 20, target_pos, target_vel);
Box_initial_conditions box_initial_conditions(75, 250);
In_box_cyl accept(5, 50, target_pos, target_vel);
Uniform_sphere_escape_velocity_cutoff uniform_sphere_escape_velocity_cutoff(75, 1.82777387E+07, 9.86242602E+00);
Scattering_experiment scattering_experiment("results.dat", t_max, 1000000000L, box_initial_conditions, accept);
Scattering_experiment scattering_experiment("results.dat", t_max, 1000000000L, uniform_sphere_escape_velocity_cutoff, accept);
scattering_experiment.launch();
std::cout << "Bye\n";