simulation.go

package main

func updateForcesAndBodies(forces []Vector, bodies []Body, dt float64) {
	for i := 0; i < len(bodies); i++ {
		for j := i + 1; j < len(bodies); j++ {
			// Grav force of bodies[j] on bodies[i]
			var f Vector = bodies[i].GravitationalForce(bodies[j])
			forces[i] = forces[i].Add(f)

			// Force of bodies[i] on bodies[j] is the negation
			forces[j] = forces[j].Add(f.Scale(-1))
		}

		// By the time we reach this point, all forces concerning bodies[i] have been counted for
		bodies[i].UpdateBodyKinematics(forces[i], dt)
	}
}

func BarnesHutUpdateForcesAndBodies(forces []Vector, bodies []Body, n Node, dt float64) {
	for i := 0; i < len(bodies); i++ {
		forces[i] = n.BarnesHut(bodies[i])
		bodies[i].UpdateBodyKinematics(forces[i], dt)
	}
}

func totalMomentum(bodies []Body) Vector {
	momentum := Vector{}

	for i := range bodies {
		momentum = momentum.Add(bodies[i].Momentum())
	}

	return momentum
}