static public double Etot(this INBodyState state)
{
double ekin = Ekin(state);
double epot = Epot(state);
return(ekin + epot);
}
static public double Epot(this INBodyState state)
{
double epot = 0.0;
var N = state.N;
var eps2 = state.eps * state.eps;
Parallel.For(0, N, i =>
// for (int i = 0; i < N; i++)
{
var RDiff = new Vector3();
var ri = state.r[i];
var mi = state.m[i];
for (int j = 0; j < N; j++)
{
if (j != i)
{
var rj = state.r[j];
//var RDiff = (state.r[j] - ri);
RDiff.c0 = rj.c0 - ri.c0;
RDiff.c1 = rj.c1 - ri.c1;
RDiff.c2 = rj.c2 - ri.c2;
var R2 = RDiff * RDiff;
epot += mi * state.m[j] / Math.Sqrt(R2 + eps2);
}
}
});
epot *= -state.G;
return(epot);
}
private static void CheckComputationOfEpot(INBodyState newState, double epot)
{
var revState = new LeapFrogState(newState as LeapFrogState);
revState.position.Reverse();
revState.velocity.Reverse();
revState.mass.Reverse();
var revEpot = revState.Epot();
if (!CompareDouble(revEpot, epot))
{
Console.Error.WriteLine("Epot = {0}, Epot rev = {1}", epot, revEpot);
}
}
private static void CheckComputationOfEpot(INBodyState newState, double epot)
{
var revState = new LeapFrogState(newState as LeapFrogState);
revState.position.Reverse();
revState.velocity.Reverse();
revState.mass.Reverse();
var revEpot = revState.Epot();
if (!CompareDouble(revEpot, epot))
{
Console.Error.WriteLine("Epot = {0}, Epot rev = {1}", epot, revEpot);
}
}
static public Vector3 A_onFirstFromAll(this INBodyState s, int first)
{
var N = s.N;
var tmp = new Vector3();
Vector3 acc = s.A_onFirstFromSecond(first, 0);
for (int i = 1; i < N; i++)
{
acc += s.A_onFirstFromSecond(first, i);
}
return(acc);
}
static public double Ekin(this INBodyState state)
{
double ekin = 0.0;
var N = state.N;
Parallel.For(0, N, i =>
// for (int i = 0; i < N; i++)
{
var v = state.v[i];
double m = state.m[i];
ekin += m * (v * v);
});
ekin *= 0.5;
return(ekin);
}
public EulerState(INBodyState other)
{
currentTime = other.t;
N = other.N;
G = other.G;
eps = other.eps;
mass = new List <double>(other.m);
position = new List <Vector3>(N);
velocity = new List <Vector3>(N);
for (int i = 0; i < N; i++)
{
position.Add(new Vector3(other.r[i]));
velocity.Add(new Vector3(other.v[i]));
}
}
static public Vector3 A_onFirstFromSecond(this INBodyState s, int first, int second)
{
var r1 = s.r[first];
var r2 = s.r[second];
var Rdiff = r2 - r1;
double R2 = Rdiff * Rdiff;
double R = Math.Sqrt(R2);
var eps = s.eps;
double eps2 = eps * eps;
double factor = s.m[second] * s.G / (R * (R2 + eps * eps));
Rdiff *= factor;
return(Rdiff);
}
public static void Serialize(this INBodyState s, double?ekin, double?epot, StringBuilder sb)
{
sb.AppendLine(s.t.ToString() + " # t");
sb.AppendLine(s.N.ToString() + " # N");
sb.AppendLine(s.G.ToString() + " # G");
sb.AppendLine(s.eps.ToString() + " # eps");
ekin = ekin ?? s.Ekin();
epot = epot ?? s.Epot();
sb.AppendLine(ekin.ToString() + " # Ekin");
sb.AppendLine(epot.ToString() + " # Epot");
foreach (var m in s.m)
{
sb.AppendLine(m.ToString());
}
foreach (var r in s.r)
{
sb.AppendLine(r.ToString());
}
foreach (var v in s.v)
{
sb.AppendLine(v.ToString());
}
}
public static Vector3[] ComputeAccelerationVectorDirect(this INBodyState s)
{
var N = s.N;
var accVector = new Vector3[N];
// compute accelerations
Parallel.For(0, N, i =>
{
accVector[i] = new Vector3();
var avi = accVector[i];
for (int j = 0; j < N; j++)
{
if (j != i)
{
var a = s.A_onFirstFromSecond(i, j);
avi.c0 += a.c0;
avi.c1 += a.c1;
avi.c2 += a.c2;
}
}
});
return(accVector);
}
public MultiStepState(INBodyState state)
: base(state)
{
}
public LeapFrogState(INBodyState state)
: base(state)
{
m_timeOfAccelerationCalculated = -1.0;
m_accelerations = null;
}
public EulerState(INBodyState other)
{
currentTime = other.t;
N = other.N;
G = other.G;
eps = other.eps;
mass = new List<double>(other.m);
position = new List<Vector3>(N);
velocity = new List<Vector3>(N);
for (int i = 0; i < N; i++)
{
position.Add( new Vector3(other.r[i]) );
velocity.Add( new Vector3(other.v[i]) );
}
}
public MultiStepState(INBodyState state)
: base(state)
{
}
public LeapFrogState(INBodyState state)
: base(state)
{
m_timeOfAccelerationCalculated = -1.0;
m_accelerations = null;
}
