https://github.com/aoshimash/hermite

A hermite integrator for planetary N-body simulation
https://github.com/aoshimash/hermite

astrophysics cpp n-body

Last synced: 10 days ago
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A hermite integrator for planetary N-body simulation

• Host: GitHub
• URL: https://github.com/aoshimash/hermite
• Owner: aoshimash
• Created: 2019-03-12T08:06:59.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2019-09-08T12:53:30.000Z (over 5 years ago)
• Last Synced: 2024-10-26T17:24:21.929Z (about 2 months ago)
• Topics: astrophysics, cpp, n-body
• Language: C++
• Homepage:
• Size: 500 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# hermite

Hermite integrator for planetary N-body simulation

## Usage

### Test

``` sh

$ cd {PROJECT_ROOT}/build

$ cmake ..

$ make

$ ctest -V

```

### Demo

``` sh

$ cd {PROJECT_ROOT}/build

$ cmake ..

$ make

$ cd demo

$ ./twobody

$ jupyter-lab --notebook-dir .

```

### Example

``` cpp

#include "hermite.h"

#include "cs.h"

#include 

#include 

#include 

#include 

#include 

#include 

// Parameters

std::size_t rep = 3;

int log2_dt_max = -5;

int log2_dt_min = -10;

double eps = 0.0;

double alpha = 1.0;

double eta_s = 0.01;

double eta = 0.03;

// Calculate initial position and velocity from orbital elements

std::valarray mass = {1.0, 1e-3};

cs::OrbitalElement oelem0(1.0, 0.1, M_PI, 0.0, 0.0, M_PI);

vector init_oelems {oelem0};

vector> pos_init(mass.size(), valarray(cs::DIM));

vector> vel_init(mass.size(), valarray(cs::DIM));

cs::ConvertOelemToCartesian(mass, init_oelems, &init_pos, &init_vel);

// Set solver

hermite::Hermite4thSolver h4sol(rep, exp_dt_max, exp_dt_min, eps, alpha, eta_s, eta);

h4sol.set_mass(mass);

h4sol.set_pos(init_pos);

h4sol.set_vel(init_vel);

h4sol.setup();

// Set output file

ofstream ofs(filename);

if (!ofs) {

  cerr << "File Open Error: \"" << filename << "\"" << endl;

  exit(EX_CANTCREAT);

}

// Start orbital calculation

double t = 0.0;

double t_stop = 10.0;

auto pos = h4sol.get_pos();

auto vel = h4sol.get_vel();

while (t < t_stop) {

  cs::WritePosVel(t, pos, vel, &ofs);

  h4sol.step_forward(&t);

  pos = h4sol.get_pos();

  vel = h4sol.get_vel();

}

```

## References

- Kokubo, E., Makino, J., 2004, PASJ, 56, 861

- Kokubo, E., Yoshinaga, K., Makino, J., 1998, MNRAS, 297, 1067