public double Evolve(double time, GravityState gravityState, ref byte[] info)
{
double[] mass = gravityState.m;
double[,] pos = gravityState.r;
this.gravityState = gravityState;
t_offset = 0;
t_evolveStart = gravityState.GetPhysicsTime();
int nloops = 0;
if (dt > time)
{
dt = time;
}
while (t_offset < time)
{
// If only one body collision time will be MAXFLOAT
t_offset += dt;
Evolve_step(ref mass, ref pos, ref info);
// timestep adjustement, relative to initial collision time
coll_time_avg = COLL_AVERAGE_FACTOR * coll_time_avg + (1 - COLL_AVERAGE_FACTOR) * coll_time;
dt = dtInitial * coll_time_avg / coll_time_initial;
if (dt > maxDt)
{
dt = maxDt;
}
else if (dt < minDt)
{
dt = minDt;
}
nloops++;
}
#pragma warning disable 162 // disable unreachable code warning
if (GravityEngine.DEBUG)
{
if (logCount++ > LOG_INTERVAL)
{
logCount = 0;
Debug.LogFormat("time={0} dt={1} coll_time={2} coll_factor={3} coll_time_initial={4} nloops={5} numbodies={6}",
time, dt, coll_time, coll_time_avg / coll_time_initial, coll_time_initial, nloops, numBodies);
}
}
#pragma warning restore 162
return(t_offset);
}
/// <summary>
/// Evolves using the force delegate. Internals differ slightly and for effeciency do not want
/// a conditional on forceDelegate in the inner loop.
///
/// </summary>
/// <returns>The force delegate.</returns>
/// <param name="time">Time.</param>
/// <param name="m">M.</param>
/// <param name="r">The red component.</param>
/// <param name="info">Info.</param>
private double EvolveForceDelegate(double time, GravityState gravityState, ref byte[] info)
{
int numSteps = 0;
double[] m = gravityState.m;
double[,] r = gravityState.r;
// advance acceleration
double r2;
double r_sep;
double f;
double timeNow = gravityState.GetPhysicsTime();
double dummy = 0;
// If objects are fixed want to use their mass but not update their position
// Better to calc their acceleration and ignore than add an if statement to core loop.
for (double t = 0; t < time; t += dt)
{
numSteps++;
// Update v and r
for (int i = 0; i < numBodies; i++)
{
if ((info[i] & GravityEngine.INACTIVE_OR_FIXED) == 0)
{
v[i, 0] += a[i, 0] * 0.5 * dt;
r[i, 0] += v[i, 0] * dt;
v[i, 1] += a[i, 1] * 0.5 * dt;
r[i, 1] += v[i, 1] * dt;
v[i, 2] += a[i, 2] * 0.5 * dt;
r[i, 2] += v[i, 2] * dt;
}
}
// a = 0
// a = 0 or init with eternal value
for (int i = 0; i < numBodies; i++)
{
if (externalAccel[i] != null)
{
double[] e_accel = externalAccel[i].acceleration(timeNow + t, gravityState, ref dummy);
a[i, 0] = e_accel[0];
a[i, 1] = e_accel[1];
a[i, 2] = e_accel[2];
}
else
{
a[i, 0] = 0.0;
a[i, 1] = 0.0;
a[i, 2] = 0.0;
}
}
// calc a
for (int i = 0; i < numBodies; i++)
{
if ((info[i] & GravityEngine.INACTIVE) == 0)
{
for (int j = i + 1; j < numBodies; j++)
{
if ((info[j] & GravityEngine.INACTIVE) == 0)
{
// O(N^2) in here, unpack loops to optimize
r2 = 0;
rji[0] = r[j, 0] - r[i, 0];
r2 += rji[0] * rji[0];
rji[1] = r[j, 1] - r[i, 1];
r2 += rji[1] * rji[1];
rji[2] = r[j, 2] - r[i, 2];
r2 += rji[2] * rji[2];
r_sep = System.Math.Sqrt(r2) + EPSILON;
f = forceDelegate.CalcPseudoForce(r_sep, i, j);
a[i, 0] += m[j] * f * (rji[0] / r_sep);
a[i, 1] += m[j] * f * (rji[1] / r_sep);
a[i, 2] += m[j] * f * (rji[2] / r_sep);
a[j, 0] -= m[i] * f * (rji[0] / r_sep);
a[j, 1] -= m[i] * f * (rji[1] / r_sep);
a[j, 2] -= m[i] * f * (rji[2] / r_sep);
}
}
}
}
// update velocity
for (int i = 0; i < numBodies; i++)
{
if ((info[i] & GravityEngine.FIXED_MOTION) == 0)
{
v[i, 0] += a[i, 0] * 0.5 * dt;
v[i, 1] += a[i, 1] * 0.5 * dt;
v[i, 2] += a[i, 2] * 0.5 * dt;
//DebugBody(i, ref m, ref r, "evolve");
}
}
// coll_time code
}
return(numSteps * dt);
}
