Optimizing gravitation calculation for particles in a zero gravity 2d space

Question

I\'ve have created a small visualisation of particles in python. I\'m caclulation the movement of particels in a 2D space with zero gravity. As each particle attracts all o

Answer 1

to do fast calculation, you need to store x, y, speedx, speedy, m in numpy arrays. For example:

import numpy as np

p = np.array([
    (0,0),
    (1,0),
    (0,1),
    (1,1),
    (2,2),
], dtype = np.float)

p is a 5x2 array which store x, y position of particles. To calculate the distance between each pair, you can use:

print np.sqrt(np.sum((p[:, np.newaxis] - p[np.newaxis, :])**2, axis=-1))

the output is:

[[ 0.          1.          1.          1.41421356  2.82842712]
 [ 1.          0.          1.41421356  1.          2.23606798]
 [ 1.          1.41421356  0.          1.          2.23606798]
 [ 1.41421356  1.          1.          0.          1.41421356]
 [ 2.82842712  2.23606798  2.23606798  1.41421356  0.        ]]

or you can use cdist from scipy:

from scipy.spatial.distance import cdist
print cdist(p, p)