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/*
* force.cc
*/
#include "def.h"
inline vect_t newton_acceleration (t_real mass, vect_t cg, vect_t pos)
{
t_real x0 = VX(pos), y0 = VY(pos), z0 = VZ(pos);
t_real x1 = VX(cg), y1 = VY(cg), z1 = VZ(cg);
t_real dx = x1 - x0, dy = y1 - y0, dz = z1 - z0;
t_real l2 = dx * dx + dy * dy + dz * dz;
t_real k = mass / (l2 * sqrt (l2));
return make_vect(k * dx, k * dy, k * dz);
}
vect_t space::calc_accel(vect_t pos)
{
switch (state) {
case ONE_PARTICLE: {
return make_vect(0.0, 0.0, 0.0);
} /* ONE_PARTICLE */
case MULTIPLE_PARTICLES: {
int idx = select_covering_rectangle(pos, area);
t_real resultx = 0.0, resulty = 0.0, resultz = 0.0;
for (int i = 0; i < N_CHILDREN; i++) {
space * s = subspaces[i];
if (i == idx) {
vect_t sv = s->calc_accel(pos);
resultx += VX(sv);
resulty += VY(sv);
resultz += VZ(sv);
} else {
if (s) {
vect_t sv = s->calc_accel1(pos);
resultx += VX(sv);
resulty += VY(sv);
resultz += VZ(sv);
}
}
}
return make_vect(resultx, resulty, resultz);
} /* MULTIPLE_PARTICLES */
default: {
printf("NO_PARTICLES!\n");
return make_vect(0.0, 0.0, 0.0); /* never reach */
} /* default */
}
}
vect_t space::calc_accel_morton(vect_t pos)
{
switch (state) {
case ONE_PARTICLE: {
return make_vect(0.0, 0.0, 0.0);
} /* ONE_PARTICLE */
case MULTIPLE_PARTICLES: {
unsigned int stride = (midx.high - midx.low) / 8;
int idx = (vect2morton(pos) - midx.low) / stride + 1;
t_real resultx = 0.0, resulty = 0.0, resultz = 0.0;
for (int i = 0; i < N_CHILDREN; i++) {
space * s = subspaces[i];
if (s && i == idx) {
vect_t sv = s->calc_accel_morton(pos);
resultx += VX(sv);
resulty += VY(sv);
resultz += VZ(sv);
} else {
if (s) {
vect_t sv = s->calc_accel1(pos);
resultx += VX(sv);
resulty += VY(sv);
resultz += VZ(sv);
}
}
}
return make_vect(resultx, resulty, resultz);
} /* MULTIPLE_PARTICLES */
default: {
printf("NO_PARTICLES!\n");
return make_vect(0.0, 0.0, 0.0); /* never reach */
} /* default */
}
}
#if 0
const t_real approx_theta = 0.67 * 0.67; /* 1.05263 */
#else
const t_real approx_theta = 1.0 * 1.0; /* 1.05263 */
#endif
vect_t space::calc_accel1(vect_t pos)
{
switch (state) {
case ONE_PARTICLE: {
return newton_acceleration(mass, cg, pos);
} /* ONE_PARTICLE */
case MULTIPLE_PARTICLES: {
t_real x0 = VX(pos), y0 = VY(pos), z0 = VZ(pos);
t_real x1 = VX(cg), y1 = VY(cg), z1 = VZ(cg);
t_real dx = x1 - x0, dy = y1 - y0, dz = z1 - z0;
t_real l2 = dx * dx + dy * dy + dz * dz;
if (diameter2 < l2 * approx_theta) {
t_real k = mass / (l2 * sqrt (l2));
return make_vect(k * dx, k * dy, k * dz);
} else {
t_real resultx = 0.0, resulty = 0.0, resultz = 0.0;
for (int i = 0; i < N_CHILDREN; i++) {
space * s = subspaces[i];
if (s) {
vect_t sv = s->calc_accel1(pos);
resultx += VX(sv);
resulty += VY(sv);
resultz += VZ(sv);
}
}
return make_vect(resultx, resulty, resultz);
}
} /* MULTIPLE_PARTICLES */
default: {
printf("NO_PARTICLES!\n");
return make_vect(0.0, 0.0, 0.0); /* never reach */
}
} /* default */
}
void particle::set_accel(space * sp)
{
#if USE_MORTON
vect_t a = sp->calc_accel_morton(pos);
#else
vect_t a = sp->calc_accel(pos);
#endif
accel = a;
}
struct thread_dat {
particle ** particles;
int begin;
int end;
space * sp;
};
void * set_accels_dac(void *args)
{
thread_dat * p = (thread_dat *) args;
if (p->end - p->begin < 5) {
for (int i = p->begin; i <= p->end; i++)
p->particles[i]->set_accel(p->sp);
} else {
int c = (p->begin + p->end - 1) / 2;
thread_dat left, right;
void * ret;
pthread_t th;
left.particles = p->particles;
left.begin = p->begin;
left.end = c;
left.sp = p->sp;
right.particles = p->particles;
right.begin = c + 1;
right.end = p->end;
right.sp = p->sp;
pthread_create(&th, NULL, set_accels_dac, (void *) &left);
set_accels_dac(&right);
pthread_join(th, (void **) ret);
}
}
void set_accels(particle ** particles, int n_particles, space * sp)
{
thread_dat data;
data.particles = particles;
data.begin = 0;
data.end = n_particles - 1;
data.sp = sp;
set_accels_dac(&data);
}
void particle::move(t_real dt)
{
vect_t vel_prime = v_plus_v (vel, k_times_v(dt, accel));
pos = v_plus_v (pos, k_times_v(dt, vel_prime));
vel = vel_prime;
}
void move_particles(particle ** particles, int n_particles, t_real dt)
{
for (int i = 0; i < n_particles; i++)
particles[i]->move(dt);
}
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