new_ca.c

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define W (1080 / 2)
#define H (1920 / 2)

#define MAX_HEADER 128

static inline uint32_t rule(const uint16_t i, const uint16_t j, const uint32_t world[W][H]) {
    uint32_t T[9], V = 0;
    uint32_t m = UINT32_MAX;
    uint32_t idx = 0;

    for (int k = 0; k < 9; k++)
        T[k] = world[(i + (k / 3) + W - 1) % W][(j + (k % 3) + H - 1) % H];

    for (int k = 0; k < 9; k++)
        V |= T[k];

    for (int k = 0; k < 9; k++) {
        uint32_t q = 5 * T[k];
        q = (q - V) ^ V;

        if (q <= m) {
            m = q;
            idx = k;
        }
    }

    return T[idx];
}

int main(void) {
    static uint32_t world[2][W][H];
    static char frame[W * H * 3 + MAX_HEADER];
    char *image;

    uint16_t i, j, k, flag = 0;

    int header_len = snprintf(frame, MAX_HEADER, "P6\n%d %d\n255\n", H, W);
    int frame_len = 3 * W * H + header_len;

    image = frame + header_len;

    srand48(time(NULL));

    for (i = 0; i < W; i++)
        for (j = 0; j < H; j++) {
            world[0][i][j] = lrand48();
        }

    while (1) {
        for (i = 0; i < W; i++) {
            for (j = 0; j < H; j++) {
                uint32_t color;
                world[!flag][i][j] = rule(i, j, world[flag]);

                color = world[!flag][i][j];

                image[3 * (i * H + j)] = color;
                image[3 * (i * H + j) + 1] = color >> 8;
                image[3 * (i * H + j) + 2] = color >> 16;
            }
        }

        flag ^= 1;

        fwrite(frame, 1, frame_len, stdout);
    }

    return 0;
}