static inline real isotropicRandomV(real r, real scaleRad1, real scaleRad2, real Mass1, real Mass2)
{
real val;
val = mw_sqrt(Mass1/mw_sqrt(mw_pow(r,2) + mw_pow(scaleRad1,2))
+ Mass2/mw_sqrt(mw_pow(r,2) + mw_pow(scaleRad2,2)));
return val;
}
/* generatePlummer: generate Plummer model initial conditions for test
* runs, scaled to units such that M = -4E = G = 1 (Henon, Heggie,
* etc). See Aarseth, SJ, Henon, M, & Wielen, R (1974) Astr & Ap, 37,
* 183.
*/
static int nbGenerateIsotropicCore(lua_State* luaSt,
dsfmt_t* prng,
unsigned int nbody,
real mass1,
real mass2,
mwbool ignore,
mwvector rShift,
mwvector vShift,
real radiusScale1,
real radiusScale2)
{
unsigned int i;
int table;
Body b;
real r, velScale;
real mass = mass1 + mass2;
real radiusScale = mw_sqrt(mw_pow(radiusScale1,2) + mw_pow(radiusScale2,2));
memset(&b, 0, sizeof(b));
velScale = mw_sqrt(mass / radiusScale); /* and recip. speed scale */
b.bodynode.type = BODY(ignore); /* Same for all in the model */
b.bodynode.mass = mass / nbody; /* Mass per particle */
lua_createtable(luaSt, nbody, 0);
table = lua_gettop(luaSt);
for (i = 0; i < nbody; ++i)
{
do
{
r = isotropicRandomR(prng, radiusScale1, radiusScale2, mass1, mass2);
/* FIXME: We should avoid the divide by 0.0 by multiplying
* the original random number by 0.9999.. but I'm too lazy
* to change the tests. Same with other models */
}
while (isinf(r));
b.bodynode.pos = isotropicBodyPosition(prng, rShift, r);
b.vel = isotropicBodyVelocity(prng, r, vShift, velScale, radiusScale1, radiusScale2, mass1, mass2);
assert(nbPositionValid(b.bodynode.pos));
pushBody(luaSt, &b);
// printf("Body %d is pushed. \n",i);
lua_rawseti(luaSt, table, i + 1);
}
return 1;
}
/* gets negative of the acceleration vector of this disk component */
static inline mwvector miyamotoNagaiDiskAccel(const Disk* disk, mwvector pos, real r)
{
mwvector acc;
const real a = disk->scaleLength;
const real b = disk->scaleHeight;
const real zp = mw_sqrt(sqr(Z(pos)) + sqr(b));
const real azp = a + zp;
const real rp = sqr(X(pos)) + sqr(Y(pos)) + sqr(azp);
const real rth = mw_sqrt(cube(rp)); /* rp ^ (3/2) */
X(acc) = -disk->mass * X(pos) / rth;
Y(acc) = -disk->mass * Y(pos) / rth;
Z(acc) = -disk->mass * Z(pos) * azp / (zp * rth);
return acc;
}
static real nbCalculateEps2(real nbody, real r0)
{
real eps = r0 / (10.0 * mw_sqrt(nbody));
real eps2 = sqr(eps);
if (eps2 <= REAL_EPSILON) {
eps2 = 2.0*REAL_EPSILON;
}
return eps2;
}
static real emdDistL2(const real* x, const real* y, void* user_param)
{
int i;
int dims = (int)(size_t)user_param;
real s = 0.0;
for (i = 0; i < dims; i++)
{
real t = x[i] - y[i];
s += t * t;
}
return mw_sqrt((real) s);
}
/* pickshell: pick a random point on a sphere of specified radius. */
static inline mwvector pickShell(dsfmt_t* dsfmtState, real rad)
{
real rsq, rsc;
mwvector vec;
do /* pick point in NDIM-space */
{
vec = mwRandomUnitPoint(dsfmtState);
rsq = mw_sqrv(vec); /* compute radius squared */
}
while (rsq > 1.0); /* reject if outside sphere */
rsc = rad / mw_sqrt(rsq); /* compute scaling factor */
mw_incmulvs(vec, rsc); /* rescale to radius given */
return vec;
}
static mwvector nbGravity_Exact(const NBodyCtx* ctx, NBodyState* st, const Body* p)
{
int i;
const int nbody = st->nbody;
mwvector a = ZERO_VECTOR;
const real eps2 = ctx->eps2;
for (i = 0; i < nbody; ++i)
{
const Body* b = &st->bodytab[i];
mwvector dr = mw_subv(Pos(b), Pos(p));
real drSq = mw_sqrv(dr) + eps2;
real drab = mw_sqrt(drSq);
real phii = Mass(b) / drab;
real mor3 = phii / drSq;
mw_incaddv(a, mw_mulvs(dr, mor3));
}
return a;
}
static real nbCalculateEps2(real nbody, real r0)
{
real eps = r0 / (10.0 * mw_sqrt(nbody));
return sqr(eps);
}
static real nbCalculateTimestep(real mass, real r0)
{
return sqr(1/10.0) * mw_sqrt((PI_4_3 * cube(r0)) / mass);
}
/*
* nbodyGravity: Walk the tree starting at the root to do force
* calculations.
*
*
* Random notes:
* - Not inlined without inline from multiple calls in
* mapForceBody(). Measurably better with the inline, but only
* slightly.
*/
static inline mwvector nbGravity(const NBodyCtx* ctx, NBodyState* st, const Body* p)
{
mwbool skipSelf = FALSE;
mwvector pos0 = Pos(p);
mwvector acc0 = ZERO_VECTOR;
const NBodyNode* q = (const NBodyNode*) st->tree.root; /* Start at the root */
while (q != NULL) /* while not at end of scan */
{
mwvector dr = mw_subv(Pos(q), pos0); /* Then compute distance */
real drSq = mw_sqrv(dr); /* and distance squared */
if (isBody(q) || (drSq >= Rcrit2(q))) /* If is a body or far enough away to approximate */
{
if (mw_likely((const Body*) q != p)) /* self-interaction? */
{
real drab, phii, mor3;
/* Compute gravity */
drSq += ctx->eps2; /* use standard softening */
drab = mw_sqrt(drSq);
phii = Mass(q) / drab;
mor3 = phii / drSq;
acc0.x += mor3 * dr.x;
acc0.y += mor3 * dr.y;
acc0.z += mor3 * dr.z;
if (ctx->useQuad && isCell(q)) /* if cell, add quad term */
{
real dr5inv, drQdr, phiQ;
mwvector Qdr;
/* form Q * dr */
Qdr.x = Quad(q).xx * dr.x + Quad(q).xy * dr.y + Quad(q).xz * dr.z;
Qdr.y = Quad(q).xy * dr.x + Quad(q).yy * dr.y + Quad(q).yz * dr.z;
Qdr.z = Quad(q).xz * dr.x + Quad(q).yz * dr.y + Quad(q).zz * dr.z;
/* form dr * Q * dr */
drQdr = Qdr.x * dr.x + Qdr.y * dr.y + Qdr.z * dr.z;
dr5inv = 1.0 / (sqr(drSq) * drab); /* form dr^-5 */
/* get quad. part of phi */
phiQ = 2.5 * (dr5inv * drQdr) / drSq;
acc0.x += phiQ * dr.x;
acc0.y += phiQ * dr.y;
acc0.z += phiQ * dr.z;
/* acceleration */
acc0.x -= dr5inv * Qdr.x;
acc0.y -= dr5inv * Qdr.y;
acc0.z -= dr5inv * Qdr.z;
}
}
else
{
skipSelf = TRUE; /* Encountered self */
}
q = Next(q); /* Follow next link */
}
else
{
q = More(q); /* Follow to the next level if need to go deeper */
}
}
if (!skipSelf)
{
/* If a body does not encounter itself in its traversal of the
* tree, it is "tree incest" */
nbReportTreeIncest(ctx, st);
}
return acc0;
}
