text: #include <stdio.h>
  #include <stdlib.h>
  #include <math.h>
  #include "genann.h"
  
  int main(int argc, char *argv[])
  {
      printf("GENANN example 2.\n");
      printf("Train a small ANN to the XOR function using random search.\n");
  
      /* Input and expected out data for the XOR function. */
      const double input[4][2] = {{0, 0}, {0, 1}, {1, 0}, {1, 1}};
      const double output[4] = {0, 1, 1, 0};
      int i;
  
      /* New network with 2 inputs,
       * 1 hidden layer of 2 neurons,
       * and 1 output. */
      genann *ann = genann_init(2, 1, 2, 1);
  
      double err;
      double last_err = 1000;
      int count = 0;
  
      do {
          ++count;
          if (count % 1000 == 0) {
              /* We're stuck, start over. */
              genann_randomize(ann);
          }
  
          genann *save = genann_copy(ann);
  
          /* Take a random guess at the ANN weights. */
          for (i = 0; i < ann->total_weights; ++i) {
              ann->weight[i] += ((double)rand())/RAND_MAX-0.5;
          }
  
          /* See how we did. */
          err = 0;
          err += pow(*genann_run(ann, input[0]) - output[0], 2.0);
          err += pow(*genann_run(ann, input[1]) - output[1], 2.0);
          err += pow(*genann_run(ann, input[2]) - output[2], 2.0);
          err += pow(*genann_run(ann, input[3]) - output[3], 2.0);
  
          /* Keep these weights if they're an improvement. */
          if (err < last_err) {
              genann_free(save);
              last_err = err;
          } else {
              genann_free(ann);
              ann = save;
          }
  
      } while (err > 0.01);
  
      printf("Finished in %d loops.\n", count);
  
      /* Run the network and see what it predicts. */
      printf("Output for [%1.f, %1.f] is %1.f.\n", input[0][0], input[0][1], *genann_run(ann, input[0]));
      printf("Output for [%1.f, %1.f] is %1.f.\n", input[1][0], input[1][1], *genann_run(ann, input[1]));
      printf("Output for [%1.f, %1.f] is %1.f.\n", input[2][0], input[2][1], *genann_run(ann, input[2]));
      printf("Output for [%1.f, %1.f] is %1.f.\n", input[3][0], input[3][1], *genann_run(ann, input[3]));
  
      genann_free(ann);
      return 0;
  }
  