#include <sys/time.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>

static int N=100;
#define NB_STEPS 50

double **cur_step;
double **next_step;

int comm_rank;
int comm_size;

/* initialize matrixes */
void init() {
  int i, j;

  cur_step = malloc(sizeof(double*) * N);
  next_step = malloc(sizeof(double*) * N);

  srand(time(NULL));
  for(i=0; i<N; i++) {
    cur_step[i] = calloc(N, sizeof(double));
    next_step[i] = calloc(N, sizeof(double));
  }

  int nb_hot_spots= rand()%N;
  printf("Generating %d hot spots\n", nb_hot_spots);
  for(i=0; i<nb_hot_spots; i++) {
    int posx = rand()%N;
    int posy = rand()%N;
    cur_step[posx][posy] += N*10000;
    printf("%d,%d : %lf\n", posx, posy, cur_step[posx][posy]);
  }
}

void compute() {
  int i, j;

  for(i=1; i< N-1; i++) {
    for(j=1; j< N-1; j++) {
      next_step[i][j] = (cur_step[i-1][j] + cur_step[i+1][j] +
			 cur_step[i][j-1] + cur_step[i][j+1] +
			 cur_step[i][j]) / 5;
    }
  }
  
  /* swap buffers */
  double ** tmp = cur_step;
  cur_step = next_step;
  next_step = tmp;
}


int main(int argc, char**argv) {

  char* output_file="result.dat";
  int dump=1;

  if(argc>1){
    N = atoi(argv[1]);
  }

  struct timeval t1, t2;
  init();

  gettimeofday(&t1, NULL);
  int i;

  for(i=0; i< NB_STEPS; i++) {
    printf("STEP %d...\n", i);
    compute();
  }

  gettimeofday(&t2, NULL);

  double total_time = ((t2.tv_sec-t1.tv_sec)*1e6 + (t2.tv_usec - t1.tv_usec))/1e6;
  printf("%d steps in %lf sec (%lf sec/step)\n",
	 NB_STEPS, total_time, total_time/NB_STEPS);
  
  return 0;
}