private static void Progress_ms2(MultiStepState state, double dt)
{
var N = state.N;
if (!state.memory.Keys.Contains("prev_acc"))
{
RungeKuttaIntegrator.Progress_rk2(new LeapFrogState(state), dt);
state.memory["prev_acc"] = (Vector3[])
state.EulerState_ComputeAccelerationVectorDirect();
}
else
{
var prev_acc = (Vector3[])state.memory["prev_acc"];
Vector3[] old_acc = state.EulerState_ComputeAccelerationVectorDirect();
var jdt = new Vector3[N];
Parallel.For(0, N, i =>
//for (int i = 0; i < N; i++)
{
jdt[i] = old_acc[i] - prev_acc[i];
state.r[i] += state.v[i] * dt + old_acc[i] * 0.5 * dt * dt;
state.v[i] += old_acc[i] * dt + jdt[i] * 0.5 * dt;
});
state.memory["prev_acc"] = old_acc;
state.currentTime += dt;
}
}
