Conway's Game of Life Accelerated with Custom Kernels in MLX

fast_conway_mlx.py

import numpy as np
import mlx.core as mx
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation

import tqdm


def conway(a: mx.array):
    source = """
        uint i = thread_position_in_grid.x;
        uint j = thread_position_in_grid.y;
        uint n = threads_per_grid.x;
        uint m = threads_per_grid.y;
        uint down = (i == 0) ? n : (i - 1);
        uint up = (i + 1) == n ? 0 : (i + 1);
        uint left = (j == 0) ? m : (j - 1);
        uint right = (j + 1) == m ? 0 : (j + 1);
        size_t idx = i * m + j;
        int count = grid[up * m + right] + grid[up * m + j]
          + grid[i * m + right] + grid[up * m + left] + grid[down * m + left]
          + grid[down * m + j] + grid[i * m + left] + grid[down * m + right];
        if ((grid[idx] && count == 2) || count == 3) {
          out[idx] = true;
        } else {
          out[idx] = false;
        }
    """
    kernel = mx.fast.metal_kernel(
        name="conway",
        input_names=["grid"],
        output_names=["out"],
        source=source,
    )
    return kernel(
        inputs=[a],
        grid=(a.shape[0], a.shape[1], 1),
        threadgroup=(2, 512, 1),
        output_shapes=[a.shape],
        output_dtypes=[a.dtype],
    )[0]


def generator(grid, steps=1000):
    for i in range(steps):
        mx.eval(grid)
        yield (~grid).astype(mx.uint8) * 255
        grid = conway(grid)


def animate(grid, steps=300, fps=30, save_as="out.mp4"):
    fig, ax = plt.subplots(figsize=(8, 4))
    im = ax.imshow(mx.zeros_like(grid), cmap="gray", vmin=0, vmax=255)

    progress_bar = tqdm.tqdm(total=steps, desc="Animating", ncols=100)

    def update(frame):
        im.set_data(frame)
        progress_bar.update(1)
        return [im]

    ani = FuncAnimation(
        fig,
        update,
        frames=generator(grid, steps=steps),
        interval=steps // fps,
        blit=True,
        cache_frame_data=False,
    )

    fig.tight_layout()
    try:
        ani.save(save_as, writer="ffmpeg", fps=fps, dpi=300)
    finally:
        progress_bar.close()

    plt.show()


if __name__ == "__main__":
    grid_size = 2048
    grid = mx.random.bernoulli(p=0.3, shape=(grid_size, grid_size))
    animate(grid)

Awesome! Here are the changes to use matplotlib instead of av for rendering and without numpy:

import mlx.core as mx
import matplotlib.pyplot as plt

from matplotlib.animation import FuncAnimation
from tqdm import tqdm

# def conway(a: mx.array): ...

# def generator(grid, steps=1000): ...

def animate(grid, steps=300, fps=30, save_as='out.mp4'):
    fig, ax = plt.subplots(figsize=(8, 4))
    im = ax.imshow(mx.zeros_like(grid), cmap='gray', vmin=0, vmax=255)

    progress_bar = tqdm(total=steps, desc='Animating', ncols=100)

    def update(frame):
        im.set_data(frame)
        progress_bar.update(1)
        return [im]

    ani = FuncAnimation(fig, update, frames=generator(
        grid, steps=steps), interval=steps // fps, blit=True, cache_frame_data=False)

    fig.tight_layout()
    try:
        ani.save(save_as, writer='ffmpeg', fps=fps, dpi=300)
    finally:
        progress_bar.close()

    plt.show()

if __name__ == "__main__":
    grid = mx.random.bernoulli(p=0.3, shape=(128, 265))
    animate(grid)

There is a bug with this code in latest mlx 0.18.0

TypeError: metal_kernel(): incompatible function arguments. The following argument types are supported:
    1. metal_kernel(name: str, input_names: collections.abc.Sequence[str], output_names: collections.abc.Sequence[str], source: str, header: str = '', ensure_row_contiguous: bool = True, atomic_outputs: bool = False) -> object

Invoked with types: kwargs = { name: str, source: str }

I updated it.

Cool!!!! Here a version with video in real time using pygame.

import numpy as np
import mlx.core as mx
import pygame

def conway(a: mx.array):
    source = """
        uint i = thread_position_in_grid.x;
        uint j = thread_position_in_grid.y;
        uint n = threads_per_grid.x;
        uint m = threads_per_grid.y;
        uint down = (i == 0) ? n : (i - 1);
        uint up = (i + 1) == n ? 0 : (i + 1);
        uint left = (j == 0) ? m : (j - 1);
        uint right = (j + 1) == m ? 0 : (j + 1);
        size_t idx = i * m + j;
        int count = grid[up * m + right] + grid[up * m + j]
          + grid[i * m + right] + grid[up * m + left] + grid[down * m + left]
          + grid[down * m + j] + grid[i * m + left] + grid[down * m + right];
        if ((grid[idx] && count == 2) || count == 3) {
          out[idx] = true;
        } else {
          out[idx] = false;
        }
    """
    kernel = mx.fast.metal_kernel(
        name="conway",
        input_names=["grid"],
        output_names=["out"],
        source=source,
    )
    return kernel(
        inputs=[a],
        grid=(a.shape[0], a.shape[1], 1),
        threadgroup=(2, 512, 1),
        output_shapes=[a.shape],
        output_dtypes=[a.dtype],
    )[0]

def run_game(grid, fps=30):
    pygame.init()
    pygame.display.set_caption("Apple MLX Conway's Game of Life")

    window_size = (800, 800)
    screen = pygame.display.set_mode(window_size)
    clock = pygame.time.Clock()

    grid_height, grid_width = grid.shape

    initial_zoom = min(window_size[0] / grid_width, window_size[1] / grid_height)
    zoom = initial_zoom

    dragging = False
    drag_start = None
    view_offset = [0, 0]

    running = True
    step = 0

    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False

            elif event.type == pygame.KEYDOWN:
                if event.key in (pygame.K_PLUS, pygame.K_EQUALS):
                    zoom *= 1.1
                elif event.key == pygame.K_MINUS:
                    zoom = max(initial_zoom, zoom / 1.1)

            elif event.type == pygame.MOUSEWHEEL:
                if event.y > 0:
                    zoom *= 1.1
                elif event.y < 0:
                    zoom = max(initial_zoom, zoom / 1.1)
                    
            elif event.type == pygame.MOUSEBUTTONDOWN:
                if event.button == 1:  # Left mouse button
                    dragging = True
                    drag_start = event.pos
            elif event.type == pygame.MOUSEBUTTONUP:
                if event.button == 1:
                    dragging = False
            elif event.type == pygame.MOUSEMOTION:
                if dragging:
                    dx = event.pos[0] - drag_start[0]
                    dy = event.pos[1] - drag_start[1]
                    view_offset[0] -= dx
                    view_offset[1] -= dy
                    drag_start = event.pos

        frame = (~grid).astype(mx.uint8) * 255
        mx.eval(frame)
        frame_np = np.array(frame)

        frame_rgb = np.stack([frame_np] * 3, axis=-1)  

        surface = pygame.surfarray.make_surface(frame_rgb.swapaxes(0, 1))

        scaled_width = int(grid_width * zoom)
        scaled_height = int(grid_height * zoom)
        scaled_surface = pygame.transform.scale(surface, (scaled_width, scaled_height))

        if scaled_width < window_size[0] or scaled_height < window_size[1]:
            screen.fill((0, 0, 0))
            offset_x = (window_size[0] - scaled_width) // 2
            offset_y = (window_size[1] - scaled_height) // 2
            screen.blit(scaled_surface, (offset_x, offset_y))
        else:
            x = (scaled_width - window_size[0]) // 2 + view_offset[0]
            y = (scaled_height - window_size[1]) // 2 + view_offset[1]
            
            x = max(0, min(x, scaled_width - window_size[0]))
            y = max(0, min(y, scaled_height - window_size[1]))
            
            view_offset[0] = x - (scaled_width - window_size[0]) // 2
            view_offset[1] = y - (scaled_height - window_size[1]) // 2
            
            cropped = scaled_surface.subsurface((x, y, window_size[0], window_size[1]))
            screen.blit(cropped, (0, 0))

        pygame.display.flip()

        grid = conway(grid)
        step += 1

        clock.tick(fps)

    pygame.quit()


if __name__ == "__main__":
    grid_size = 2048
    grid = mx.random.bernoulli(p=0.3, shape=(grid_size, grid_size))
    run_game(grid, fps=60)