static private void vp(List <Body> bv, int nstep)
{
MathVector dacc = MathVector.makeMathVector();
MathVector dvel = MathVector.makeMathVector();
double dthf = 0.5 * BH.DTIME;
for (int i = 0; i < bv.Count; ++i)
{
Body b = bv[i];
MathVector acc1 = b.newAcc.cloneMathVector();
if (nstep > 0)
{
dacc.subtraction2(acc1, b.acc);
dvel.multScalar2(dacc, dthf);
dvel.addition(b.vel);
b.vel = dvel.cloneMathVector();
}
b.acc = acc1.cloneMathVector();
dvel.multScalar2(b.acc, dthf);
MathVector vel1 = b.vel.cloneMathVector();
vel1.addition(dvel);
MathVector dpos = vel1.cloneMathVector();
dpos.multScalar1(BH.DTIME);
dpos.addition(b.pos);
b.pos = dpos.cloneMathVector();
vel1.addition(dvel);
b.vel = vel1.cloneMathVector();
}
}
/**
* Descend tree finding center of mass coordinates
*
* @return the mass of this node
*/
public override double hackcofm()
{
double mq = 0.0;
MathVector tmpPos = MathVector.makeMathVector();
MathVector tmpv = MathVector.makeMathVector();
for (int i = 0; i < NSUB; i++)
{
Node r = this.subp[i];
if (r != null)
{
double mr = r.hackcofm();
mq = mr + mq;
tmpv.multScalar2(r.pos, mr);
tmpPos.addition(tmpv);
}
}
mass = mq;
pos = tmpPos;
pos.divScalar(mass);
return(mq);
}
/**
* Create the testdata used in the benchmark.
*
* @param nbody the number of bodies to create
*/
public void createTestData(int nbody)
{
MathVector cmr = MathVector.makeMathVector();
MathVector cmv = MathVector.makeMathVector();
bodyTab = new List <Body>();
double rsc = 3.0 * 3.1415 / 16.0;
double vsc = Math.Sqrt(1.0 / rsc);
double seed = 123.0;
int k;
for (int i = 0; i < nbody; i++)
{
Body p = Body.makeBody();
bodyTab.Add(p);
p.mass = 1.0 / (double)nbody;
seed = BH.myRand(seed);
double t1 = BH.xRand(0.0, 0.999, seed);
t1 = Math.Pow(t1, (-2.0 / 3.0)) - 1.0;
double r = 1.0 / Math.Sqrt(t1);
double coeff = 4.0;
for (k = 0; k < MathVector.NDIM; k++)
{
seed = BH.myRand(seed);
r = BH.xRand(0.0, 0.999, seed);
p.pos.setValue(k, coeff * r);
}
cmr.addition(p.pos);
double x = 0.0;
double y = 0.0;
do
{
seed = BH.myRand(seed);
x = BH.xRand(0.0, 1.0, seed);
seed = BH.myRand(seed);
y = BH.xRand(0.0, 0.1, seed);
} while(y > x * x * Math.Pow(1.0 - x * x, 3.5));
double v = Math.Sqrt(2.0) * x / Math.Pow(1.0 + r * r, 0.25);
double rad = vsc * v;
double rsq = 0.0;
do
{
for (k = 0; k < MathVector.NDIM; k++)
{
seed = BH.myRand(seed);
p.vel.setValue(k, BH.xRand(-1.0, 1.0, seed));
}
rsq = p.vel.dotProduct();
} while(rsq > 1.0);
double rsc1 = rad / Math.Sqrt(rsq);
p.vel.multScalar1(rsc1);
cmv.addition(p.vel);
}
cmr.divScalar((double)nbody);
cmv.divScalar((double)nbody);
this.bodyTabRev = new List <Body>();
for (int j = 0; j < this.bodyTab.Count; ++j)
{
Body b = this.bodyTab[j];
b.pos.subtraction1(cmr);
b.vel.subtraction1(cmv);
this.bodyTabRev.Add(b);
}
}