# Particula Numerica

Here is an overview of Particula Numerica 3.0.

Particula is a physical simulator to simulate a system of many point masses using the equation of motion. Particula shows the dynamics of the masses beginning from a certain initial condition. In the field of astrophysics, this kind of simulator is called N-Body simulator.

N-Body simulators calculate the all forces between the every two of them and accumulate the total forces for each body. Then using the evaluated forces, the simulators solve the equation of motion of each body.

The basic algorithm are quite simple, but in the case of large N, there is a serious problem.

The total amount of computation become quite large in the order of square of N calculation for gravity forces. This is very serious problem with large N. As for molecular dynamics or plasma simulator could be neglect the force from the bodies in a far area. This is because the electromagnetic force are composed of positive and negative forces, often there are canceled each other. But the force of gravity only has an attractive force so the effect of force cannot be eliminated.

So an algorithm to reduce the computaion by merging masses into single mass point in a distant area using octet-tree area division. Particula has the algorithm and moreover an original method is implemented using Alternate digital tree algorithm.