void convert_inputs(double in_params[][2], double* out_params) {
out_params[0] = convert_mass(in_params[0][0], in_params[0][1]);
out_params[1] = convert_length(in_params[1][0], in_params[1][1]);
out_params[2] = convert_energy(in_params[2][0], in_params[2][1]);
if (DEBUG) {
for (int i = 0; i < 3; i++) {
printf("%3.8f\r\n", out_params[i]);
}
}
}
int check_fast_approaches( struct particle *parts,
struct particle *p, struct particle *pk/*,
double r_2*/)
{
_enter_function(_UL_TIMESTEP, _UL_TIMESTEP_CHECK_FAST_APPROACHES);
int i, collision=0;
double temp, r_close_2=-1., r_temp_2, t_close, dt=.0, dt2=.0, dt3=.0, dt4=.0, dt5=.0;
double *px=p->x, *pv=p->v, *pkx, *pkv, r_2;
double x[3], v[3], a[3], a_[3];
assert(p != pk);
add_over(1, &count_approach_checks, &count_approach_checks_over);
if(pk->active)
{
pkx = pk->x;
pkv = pk->v;
}
else
// have to use predicted x, v and corrected derivatives
{
#ifndef USE_GRAPE
pkx = pk->xp;
#else
pkx = pk->x;
#endif
pkv = pk->v;
dt = p->t - pk->t;
dt2 = .5 * dt * dt;
dt3 = dt * dt2 * _1_3;
dt4 = .25 * dt * dt3;
dt5 = .2 * dt * dt4;
}
for(i = 0; i < 3; i++)
{
if( 1
#ifdef USE_GRAPE
&& pk->active
#endif
)
{
x[i] = px[i] - pkx[i];
}
else
{
x[i] = px[i] - (pkx[i]
+ dt * pk->v[i]
+ dt2 * (pk->a[i] + pk->ha[i])
+ dt3 * (pk->a_[i] + pk->ha_[i])
+ dt4 * (pk->a_2[i] + pk->ha_2[i])
#ifndef USE_GRAPE
+ dt5 * (pk->a_3[i] + pk->ha_3[i])
#endif
);
}
if(pk->active)
{
v[i] = pv[i] - pkv[i];
a[i] = p->ha[i] + p->a[i] - pk->ha[i] - pk->a[i];
a_[i] = p->ha_[i] + p->a_[i] - pk->ha_[i] - pk->a_[i];
}
else
{
v[i] = pv[i] - (pkv[i]
+ dt * (pk->a[i] + pk->ha[i])
+ dt2 * (pk->a_[i] + pk->ha_[i])
+ dt3 * (pk->a_2[i] + pk->ha_2[i])
#ifndef USE_GRAPE
+ dt4 * (pk->a_3[i] + pk->ha_3[i])
#endif
);
a[i] = p->ha[i] + p->a[i] - (pk->a[i] + pk->ha[i]
+ dt * (pk->a_[i] + pk->ha_[i])
+ dt2 * (pk->a_2[i] + pk->ha_2[i])
#ifndef USE_GRAPE
+ dt3 * (pk->a_3[i] + pk->ha_3[i])
#endif
);
a_[i] = p->ha_[i] + p->a_[i] - (pk->a_[i] + pk->ha_[i]
+ dt * (pk->a_2[i] + pk->ha_2[i])
#ifndef USE_GRAPE
+ dt2* (pk->a_3[i] + pk->ha_3[i])
#endif
);
}
}
r_2 = scal_prod(x, x);
// linear approximation of time of closest encounter
//t_close = -scal_prod(x, v) / scal_prod(v, v);
// 2nd order approximation of time of closest encounter
double xv, xa, v2, va, a2, _p, _q, _p3, _q2, _d, _u, _v, dy, t2, t3, _1_a2;
xv = scal_prod(x, v);
xa = scal_prod(x, a);
v2 = scal_prod(v, v);
va = scal_prod(v, a);
a2 = scal_prod(a, a);
_1_a2 = 1. / a2;
dy = - va * _1_a2;
_p = (a2 * 2.* (v2 + xa) - 3. * va * va) * (_1_a2 * _1_a2);
_p3 = _p * _p * _p;
_q = (2. * va * va * va - va * 2.*(v2 + xa) * a2 + 2. * xv * a2 * a2) * (_1_a2 * _1_a2 * _1_a2);
_q2 = _q * _q;
_d = 4. * _p3 + 27. * _q2;
if(_d > 0)
{
_u = -.5 * _q;
_v = sqrt(.25 * _q2 + _p3 * _1_27);
t_close = cbrt(_u + _v) + cbrt(_u - _v) + dy;
}
else if(_d == 0)
{
t_close = cbrt(.5 * _q) + dy;
t3 = cbrt(-4. * _q) + dy;
if(t3 > 0 && (t3 < t_close || t_close <= 0))
{
t_close = t3;
}
}
else // _d < 0
{
_u = sqrt(-4. *_1_3 * _p);
_v = acos(-.5 * _q * sqrt(-27. / _p3)) * _1_3;
t_close = _u * _v + dy;
t2 = -_u * (_v + M_PI * _1_3) + dy;
t3 = -_u * (_v - M_PI * _1_3) + dy;
if(t2 > 0 && (t2 < t_close || t_close <= 0)) t_close = t2;
if(t3 > 0 && (t3 < t_close || t_close <= 0)) t_close = t3;
}
while(1)
{
// check distance after next step
r_temp_2 = .0;
for(i = 0; i < DIMENSIONS; i++)
{
temp = x[i] + p->dt * (v[i] + p->dt * .5 * (a[i] /*+ p->dt / 3. * a_[i]*/));
r_temp_2 += temp * temp;
}
if(r_2 > r_temp_2 * MAX_APPROACH_FACTOR_2 || r_2 * MAX_APPROACH_FACTOR_2 < r_temp_2)
{
add_over(1, &count_approach_reduce_t, &count_approach_reduce_t_over);
#ifdef DEBUG_ALL
fprintf(get_file(FILE_DEBUG),
"\t# halving dt: approach m%d - m%d: \tr(t=%1.6e)=%1.2e\t\tr(t=%1.6e)=%1.2e\n",
pk->name, p->name,
t_total(p->t), convert_length(sqrt(r_2), 0),
t_total(p->t+p->dt), convert_length(sqrt(r_temp_2), 0));
fflush(get_file(FILE_DEBUG));
#endif
p->dt *= .5;
#ifdef SYNCHRONIZE_APPROACHING_TIMESTEPS
if(!pk->active)
{
while(pk->htlast + .5 * pk->dt > p->t + p->dt + DT_TOLERANCE)
{
pk->dt *= .5;
#ifdef DEBUG_ALL
fprintf(get_file(FILE_DEBUG),
"#### [t=%1.12e] shrinking timestep for m%d as of close encounter with m%d to %e ####\n",
t_total(p->t),
pk->name,
p->name,
t_total(pk->dt));
fflush(get_file(FILE_DEBUG));
#endif
}
}
#endif
continue;
}
if(r_2 < 9. * C_2G_C2 * C_2G_C2 * (pk->m + p->m) * (pk->m + p->m))
{
// collision in 3 Schwarzschild-radii
collision = 1;
fprintf(get_file(FILE_WARNING), "#### [t=%1.12e] COLLISION of m%d and m%d at %1.12e: %e (r_S = %e) ####\n",
t_total(p->t),
p->name,
pk->name,
t_total(p->t + t_close),
convert_length(sqrt(r_2), 0),
convert_length(C_2G_C2 * (pk->m + p->m), 0));
fflush(get_file(FILE_WARNING));
}
if(t_close > .0 && t_close < p->dt)
{
// close encounter will happen _during_ next step, now calculate distance
if(r_close_2 <.0)
{
r_close_2 = .0;
for(i = 0; i < DIMENSIONS; i++)
{
temp = (x[i] + t_close * (v[i] + .5 * t_close * a[i]));
r_close_2 += temp * temp;
}
}
if(r_close_2 < square(3. * C_2G_C2 * (pk->m + p->m)))
{
// collision in 3 Schwarzschild-radii
collision = 1;
fprintf(get_file(FILE_WARNING), "#### [t=%1.12e] COLLISION of m%d and m%d at %1.12e: %e (r_S = %e) ####\n",
t_total(p->t),
p->name,
pk->name,
t_total(p->t + t_close),
convert_length(sqrt(r_close_2), 0),
convert_length(C_2G_C2 * (pk->m + p->m), 0));
fflush(get_file(FILE_WARNING));
}
// approach to small multiple of impact parameter:
// r'_12 < warn_fact * b = warn_fact * 2 * r_1 * m / M
#ifdef WARN_CLOSEENC
if(r_close_2 * parts->m * parts->m < square(WARN_APPROACH_FACT * 2 * pk->m) * scal_prod(p->xp, p->xp)
&& (N_MAX_DETAIL < -1 || p->name <= N_MAX_DETAIL || pk->name <= N_MAX_DETAIL)
)
{
fprintf(get_file(FILE_WARNING),
"\t# predicted close encounter m%d - m%d: \tr(t=%1.6e)=%1.2e\t\tr(t=%1.6e)=%1.2e=%1.2fb\tp.dt=%1.2e\tpk->dt=%1.2e (%1.2e el.) [%d:%d]\n",
pk->name, p->name,
t_total(p->t), convert_length(sqrt(r_2), 0),
t_total(p->t + t_close), convert_length(sqrt(r_close_2), 0),
sqrt(r_close_2) / (2. * v_abs(p->xp) * pk->m) * parts->m,
convert_time(p->dt, 0),
convert_time(pk->dt, 0),
convert_time(p->t - pk->t, 0),
pk->nearestneighbour, p->nearestneighbour);
fprintf(get_file(FILE_WARNING),
" PCE %1.12e\t%d\t%e\t%1.10e\t%1.10e\t%1.10e\t%1.10e\t%1.10e\t%1.10e\t%d\t%e\t%1.10e\t%1.10e\t%1.10e\t%1.10e\t%1.10e\t%1.10e\n",
t_total(p->t),
pk->name, convert_mass(pk->m, 0),
convert_length(pkx[0], 0), convert_length(pkx[1], 0), convert_length(pkx[2], 0),
convert_length(convert_time(pkv[0], 1), 0), convert_length(convert_time(pkv[1], 1), 0), convert_length(convert_time(pkv[2], 1), 0),
p->name, convert_mass(p->m, 0),
convert_length(px[0], 0), convert_length(px[1], 0), convert_length(px[2], 0),
convert_length(convert_time(pv[0], 1), 0), convert_length(convert_time(pv[1], 1), 0), convert_length(convert_time(pv[2], 1), 0)
);
fflush(get_file(FILE_WARNING));
}
#endif
if(r_2 > MAX_APPROACH_FACTOR_2 * r_close_2)
{
add_over(1, &count_approach_reduce_t, &count_approach_reduce_t_over);
#ifdef DEBUG_ALL
fprintf(get_file(FILE_DEBUG),
"\t# halving dt: encounter m%d - m%d: \tr(t=%1.6e)=%1.2e\t\tr(t=%1.6e)=%1.2e\tstep: t=%1.6e\n",
pk->name, p->name,
t_total(p->t), convert_length(sqrt(r_2), 0),
t_total(p->t + t_close), convert_length(sqrt(r_close_2), 0),
t_total(p->t + p->dt));
fflush(get_file(FILE_DEBUG));
#endif
p->dt *= .5;
#ifdef SYNCHRONIZE_APPROACHING_TIMESTEPS
if(!pk->active)
while(pk->htlast + .5 * pk->dt > p->t + p->dt + DT_TOLERANCE)
{
pk->dt *= .5;
#ifdef DEBUG_ALL
fprintf(get_file(FILE_DEBUG),
"#### shrinking. timestep for m%d as of close encounter with m%d to %e ####\n",
t_total(p->t),
pk->name,
p->name,
t_total(pk->dt));
#endif
}
#endif
continue;
}
}
break;
}
_exit_function();
return collision;
}
