Advance of https://gist.github.com/linnil1/ddd94835d73a66646a061374a6d495c9

heat_dynamic_grid.py

import numpy as np
import matplotlib.pyplot as plt

want_size = [1000, 1000]
esp = 1e-1
label_num = 40
max_iter = None
it = 0


def setBound():
    grid[0, :] = 50
    grid[:, -1] = 100
    grid[-1, :] = 200
    grid[:, 0] = 300


def goIter():
    global it, grid
    oldit = it
    print(nowsize)

    while True:
        it += 1
        oldgrid = grid.copy()
        grid = np.mean([
            np.roll(grid, 1, axis=0),
            np.roll(grid, 1, axis=1),
            np.roll(grid, -1, axis=0),
            np.roll(grid, -1, axis=1)], axis=0)
        setBound()
        # print(it)
        # print(grid)
        if not (np.abs(grid - oldgrid) > esp).any():
            break
        if max_iter and it >= max_iter:
            break
    print(it - oldit)


def extendMatrix(axis):
    global grid
    new_len = min(nowsize[axis] * 2, want_size[axis])
    ind = (np.arange(new_len) * nowsize[axis] / new_len).astype(np.int)
    nowsize[axis] = new_len
    grid = np.take(grid, ind, axis=axis)


nowsize = np.array([3, 3])
grid = np.zeros(nowsize)
setBound()
goIter()

while any(nowsize != want_size):
    extendMatrix(0)
    extendMatrix(1)
    setBound()
    goIter()


X, Y = np.meshgrid(np.arange(want_size[0]), np.arange(want_size[1]))
# cont = plt.contourf(X, Y, grid, label_num)
plt.figure(figsize=(16, 12), dpi=200)
cont = plt.contour(X, Y, grid, label_num)
plt.clabel(cont)
plt.xticks([])
plt.yticks([])
plt.subplots_adjust(top=1, bottom=0, right=1, left=0,
                    hspace=0, wspace=0)
plt.savefig('heat_dynamic_grid.png', bbox_inches='tight')
plt.show()