snlite reaction diffusion test

RD_test4.py

"""
in steps s d=40 n=2
out nparray s
out nparray2 s
"""

import numpy as np
from numpy import zeros, random


# pylint: disable=c0103

n = 100  # size of grid n*n
Dh = 1. / n  # spatial res, assuming space is [0, 1] * [0, 1]
Dt = 0.02 # temporal res

a, b, c, d, h, k = 1., -1, 2., -1.5, 1., 1. # param values
Du = 0.0001  # diffusion constant of U
Dv = 0.0006  # dif  V

def initialize():
    global u, v, nextu, nextv
    u = zeros([n, n])
    v = zeros([n, n])
    for x in range(n):
        for y in range(n):
            u[x, y] = 1. + random.uniform(-0.03, 0.03)  # small noise is added
            v[x, y] = 1. + random.uniform(-0.03, 0.03)  # small noise is added
    nextu = zeros([n, n])
    nextv = zeros([n, n])

def update():
    global u, v, nextu, nextv
    for x in range(n):
        for y in range(n):
            # state-transition function
            uC, uR, uL, uU, uD = u[x, y], u[(x+1) % n, y], u[(x-1)%n, y], u[x, (y+1) % n], u[x, (y-1) % n]
            vC, vR, vL, vU, vD = v[x, y], v[(x+1) % n, y], v[(x-1)%n, y], v[x, (y+1) % n], v[x, (y-1) % n]

            uLap = (uR + uL + uU + uD - 4 * uC) / (Dh**2)
            vLap = (vR + vL + vU + vD - 4 * vC) / (Dh**2)
            nextu[x, y] = uC + (a*(uC-h) + b*(vC-k) + Du * uLap) * Dt
            nextv[x, y] = vC + (c*(uC-h) + d*(vC-k) + Dv * vLap) * Dt

    u, nextu = nextu, u
    v, nextv = nextv, v

initialize()
for iteration in range(steps):
    update()

nparray.append(u.ravel())
nparray2.append(v.ravel())