Fast and minimal C ECA implementation

Methods

The following methods are available in the header "fast_eca/wolfram_automaton.h":

• autom_t* create_automat(size_t size, int states): This creates a pointer to an autom_t structure, representing an automaton of size size with states states.
• int init_automat(autom_t* autom, enum InitMode mode): Initializes the automaton with:
  1. One cell in state 1 in the middle of the grid and the rest to 0 if mode == ONE
  2. Random states if mode == RANDOM
• uint8_t* rule_from_number(unsigned long rule_number, int states, int neighbors): Creates an ECA rule (array of uint8_t) from its number, number of states and neighborhood size.
• int update_step(autom_t* autom, uint8_t* rule, int radius): Updates the automaton one step at a time with the rule and radius (radius is neighbords/2 - 1).
• int print_autom(autom_t* autom, char* buf): Format the automaton to a buffer. The buffer needs to be allocated to at least the size of (size + 1) char.

Try it out

Clone this folder in your project.

git clone https://github.com/hugcis/fast_eca.git

Put this C code into a file main.c, next to the folder fast_eca:

#include <stdio.h>
#include <inttypes.h>
#include "fast_eca/wolfram_automaton.h"

int main(int argc, char** argv) {
  size_t size = atoi(argv[1]);
  int neighbors = 3;
  int radius = (neighbors - 1) / 2;
  int states = 2;

  uint8_t* rule = rule_from_number(atoi(argv[2]), states, neighbors);
  autom_t* autom = create_automat(size, states);
  char* buf = calloc(size + 1, sizeof(char));
  init_automat(autom, ONE);

  for (int i = 0; i < 100; ++i) {
    update_step(autom, rule, radius);
    print_autom(autom, buf);
    fprintf(stdout, "%s\n", buf);
  }
}

Compile with the following command:

gcc -O3 -o main main.c -I. fast_eca/wolfram_automaton.c

And run (Grid size 100, rule 110)

./main 100 110