int main(int argc, char* argv[]){
struct reb_simulation* r = reb_create_simulation();
r->dt = 0.0012*2.*M_PI; // initial timestep
r->integrator = REB_INTEGRATOR_MERCURIUS;
r->heartbeat = heartbeat;
struct reb_particle star = {0};
star.m = 1;
reb_add(r, star);
// Add planets
int N_planets = 3;
for (int i=0;i<N_planets;i++){
double a = 1.+.1*(double)i; // semi major axis
double v = sqrt(1./a); // velocity (circular orbit)
struct reb_particle planet = {0};
planet.m = 2e-5;
planet.x = a;
planet.vy = v;
reb_add(r, planet);
}
reb_move_to_com(r); // This makes sure the planetary systems stays within the computational domain and doesn't drift.
e_init = reb_tools_energy(r);
system("rm -rf energy.txt");
reb_integrate(r, INFINITY);
}
int main(int argc, char* argv[]){
struct reb_simulation* r = reb_create_simulation();
// Setup constants
r->dt = 4; // in days
tmax = 7.3e10; // 200 Myr
r->G = 1.4880826e-34; // in AU^3 / kg / day^2.
r->ri_whfast.safe_mode = 0; // Turn off safe mode. Need to call reb_integrator_synchronize() before outputs.
r->ri_whfast.corrector = 11; // 11th order symplectic corrector
r->integrator = REB_INTEGRATOR_WHFAST;
r->heartbeat = heartbeat;
r->exact_finish_time = 1; // Finish exactly at tmax in reb_integrate(). Default is already 1.
//r->integrator = REB_INTEGRATOR_IAS15; // Alternative non-symplectic integrator
// Initial conditions
for (int i=0;i<10;i++){
struct reb_particle p = {0};
p.x = ss_pos[i][0]; p.y = ss_pos[i][1]; p.z = ss_pos[i][2];
p.vx = ss_vel[i][0]; p.vy = ss_vel[i][1]; p.vz = ss_vel[i][2];
p.m = ss_mass[i];
reb_add(r, p);
}
reb_move_to_com(r);
e_init = reb_tools_energy(r);
system("rm -f energy.txt");
reb_integrate(r, tmax);
}
void heartbeat(struct reb_simulation* r){
if (reb_output_check(r, 10000.)){
reb_output_timing(r, tmax);
reb_integrator_synchronize(r);
FILE* f = fopen("energy.txt","a");
double e = reb_tools_energy(r);
fprintf(f,"%e %e\n",r->t, fabs((e-e_init)/e_init));
fclose(f);
}
}
void heartbeat(struct reb_simulation* r){
if (reb_output_check(r, 10.*2.*M_PI)){
reb_output_timing(r, 0);
}
if (reb_output_check(r, 2.*M_PI)){
// Once per year, output the relative energy error to a text file
FILE* f = fopen("energy.txt","a");
reb_integrator_synchronize(r);
double e = reb_tools_energy(r);
fprintf(f,"%e %e\n",r->t, fabs((e-e_init)/e_init));
fclose(f);
}
}
void reb_integrator_hermes_part2(struct reb_simulation* r){
reb_integrator_whfast_part2(r);
calc_forces_on_planets(r, r->ri_hermes.a_f);
struct reb_simulation* mini = r->ri_hermes.mini;
r->ri_hermes.steps++;
if (r->ri_hermes.mini_active){
r->ri_hermes.steps_miniactive++;
r->ri_hermes.steps_miniN += mini->N;
reb_integrate(mini,r->t);
for (int i=0; i<mini->N; i++){
r->particles[r->ri_hermes.global_index_from_mini_index[i]] = mini->particles[i];
r->particles[r->ri_hermes.global_index_from_mini_index[i]].sim = r;
}
// Correct for energy jump in collision
if(r->ri_hermes.collision_this_global_dt && r->track_energy_offset){
double Ef = reb_tools_energy(r);
r->energy_offset += r->ri_hermes.energy_before_timestep - Ef;
}
}
}
int main(int argc, char* argv[]) {
struct reb_simulation* r = reb_create_simulation();
// Setup constants
const double k = 0.01720209895; // Gaussian constant
r->dt = 40; // in days
r->G = k * k; // These are the same units as used by the mercury6 code.
r->ri_whfast.safe_mode = 0; // Turn of safe mode. Need to call integrator_synchronize() before outputs.
r->ri_whfast.corrector = 11; // Turn on symplectic correctors (11th order).
// Setup callbacks:
r->heartbeat = heartbeat;
r->force_is_velocitydependent = 0; // Force only depends on positions.
r->integrator = REB_INTEGRATOR_WHFAST;
//r->integrator = REB_INTEGRATOR_IAS15;
//r->integrator = REB_INTEGRATOR_WH;
// Initial conditions
for (int i = 0; i < 6; i++) {
struct reb_particle p;
p.x = ss_pos[i][0];
p.y = ss_pos[i][1];
p.z = ss_pos[i][2];
p.vx = ss_vel[i][0];
p.vy = ss_vel[i][1];
p.vz = ss_vel[i][2];
p.ax = 0;
p.ay = 0;
p.az = 0;
p.m = ss_mass[i];
reb_add(r, p);
}
if (r->integrator == REB_INTEGRATOR_WH) {
struct reb_particle* const particles = r->particles;
// Move to heliocentric frame (required by WH integrator)
for (int i = 1; i < r->N; i++) {
particles[i].x -= particles[0].x;
particles[i].y -= particles[0].y;
particles[i].z -= particles[0].z;
particles[i].vx -= particles[0].vx;
particles[i].vy -= particles[0].vy;
particles[i].vz -= particles[0].vz;
}
particles[0].x = 0;
particles[0].y = 0;
particles[0].z = 0;
particles[0].vx = 0;
particles[0].vy = 0;
particles[0].vz = 0;
} else {
reb_move_to_com(r);
}
r->N_active = r->N - 1; // Pluto is treated as a test-particle.
double e_initial = reb_tools_energy(r);
// Start integration
reb_integrate(r, tmax);
double e_final = reb_tools_energy(r);
printf("Done. Final time: %.4f. Relative energy error: %e\n", r->t, fabs((e_final - e_initial) / e_initial));
}
void reb_integrator_hermes_part1(struct reb_simulation* r){
r->gravity_ignore_10 = 0;
const int _N_active = ((r->N_active==-1)?r->N:r->N_active) - r->N_var;
struct reb_simulation* mini = r->ri_hermes.mini;
if (mini == NULL){
mini = reb_create_simulation();
r->ri_hermes.mini = mini;
mini->usleep = -1; // Disable visualiation
mini->integrator = REB_INTEGRATOR_IAS15;
mini->gravity = REB_GRAVITY_BASIC;
mini->dt = r->dt;
mini->additional_forces = reb_integrator_hermes_additional_forces_mini;
mini->ri_hermes.global = r; //set to != 0 so that collision.c knows to remove from both
}
mini->testparticle_type = r->testparticle_type;
mini->collision = r->collision;
mini->collision_resolve = r->collision_resolve;
mini->collision_resolve_keep_sorted = r->collision_resolve_keep_sorted;
mini->track_energy_offset = r->track_energy_offset;
mini->force_is_velocity_dependent = r->force_is_velocity_dependent;
mini->post_timestep_modifications = r->post_timestep_modifications;
// Remove all particles from mini
mini->t = r->t;
int mini_previously_active = r->ri_hermes.mini_active;
mini->N = 0;
mini->energy_offset = 0.;
r->ri_hermes.mini_active = 0;
r->ri_hermes.global_index_from_mini_index_N = 0;
r->ri_hermes.collision_this_global_dt = 0;
if (_N_active>r->ri_hermes.a_Nmax){
r->ri_hermes.a_i = realloc(r->ri_hermes.a_i,sizeof(double)*3*_N_active);
r->ri_hermes.a_f = realloc(r->ri_hermes.a_f,sizeof(double)*3*_N_active);
r->ri_hermes.a_Nmax = _N_active;
}
//reset is_in_mini
if (r->N>r->ri_hermes.is_in_mini_Nmax){
r->ri_hermes.is_in_mini_Nmax = r->N;
r->ri_hermes.is_in_mini = realloc(r->ri_hermes.is_in_mini,r->N*sizeof(int));
}
for(int i=_N_active;i<r->N;i++)r->ri_hermes.is_in_mini[i] = 0;
// Add all massive particles
for (int i=0; i<_N_active; i++){
reb_add(r->ri_hermes.mini, r->particles[i]);
r->ri_hermes.is_in_mini[i] = 1;
if (r->ri_hermes.global_index_from_mini_index_N>=r->ri_hermes.global_index_from_mini_index_Nmax){
r->ri_hermes.global_index_from_mini_index_Nmax += 32;
r->ri_hermes.global_index_from_mini_index = realloc(r->ri_hermes.global_index_from_mini_index,r->ri_hermes.global_index_from_mini_index_Nmax*sizeof(int));
}
r->ri_hermes.global_index_from_mini_index[r->ri_hermes.global_index_from_mini_index_N] = i;
r->ri_hermes.global_index_from_mini_index_N++;
}
r->ri_hermes.mini->N_active = _N_active;
reb_integrator_hermes_check_for_encounter(r);
if (r->N != r->ri_hermes.mini->N || mini_previously_active==0) {
reb_integrator_ias15_clear(r->ri_hermes.mini);
}
calc_forces_on_planets(r, r->ri_hermes.a_i);
if(r->ri_hermes.mini_active && r->track_energy_offset){
r->ri_hermes.energy_before_timestep = reb_tools_energy(r);
}
reb_integrator_whfast_part1(r);
}
