#include <stdio.h>
#include <math.h>

#ifdef _OPENMP
   #include <omp.h>
#else
   #define omp_get_thread_num() 0
   #define opm_set_num_threads() 0
   #define omp_get_num_threads() 1
#endif

#define N 100

float work(int a) {
  return a+1;
}


int main(void) {
  float a[N], b[N], x, f, sum, sum_expected, psum;
  int i;
  int num_threads;

  /* Example 1 (this example contains an OpenMP parallelization error) */
  /* --------- */

  a[0] = 0;
  // Added private(i) lastprivate(a,b) schedule(static) #pragma section
  // And:
  num_threads=omp_get_max_threads(); //Get number of threads
  printf("Trabajamos con: %d threads\n", num_threads);
# pragma omp parallel for private(i) lastprivate(a,b) schedule(static)
  for (i=1; i<N; i++) {
    a[i] = 2.0*i*(i-1);
    b[i] = a[i] - a[i-1];
  } /* end of omp parallel for */

  /* testing the correctness of the numerical result: */
  sum=0; for (i=1; i<N; i++) { sum = sum + b[i]; }
  sum_expected = a[N-1]-a[0];
  printf("Exa.1: sum  computed=%8.1f,  expected=%8.1f,  difference=%8.5f \n",
                                 sum,  sum_expected, sum-sum_expected);


  /* Example 2 (this example contains an OpenMP parallelization error) */
  /* --------- */

  a[0] = 0;

  // Changed nowait clause from first loop to second
  // And:
# pragma omp parallel
  {
#   pragma omp for private(i) schedule(static)
    for (i=1; i<N; i++){
      a[i] = 3.0*i*(i+1);
    } /* end of omp for nowait */
#   pragma omp for private(i) schedule(static) nowait
    for (i=1; i<N; i++){
      b[i] = a[i] - a[i-1];
    } /* end of omp for */
  } /* end of omp parallel */

  /* testing the correctness of the numerical result: */
  sum=0; for (i=1; i<N; i++) { sum = sum + b[i]; }
  sum_expected = a[N-1]-a[0];
  printf("Exa.2: sum  computed=%8.1f,  expected=%8.1f,  difference=%8.5f \n",
                                 sum,  sum_expected, sum-sum_expected);


  /* Example 3 (this example contains an OpenMP parallelization error) */
  /* --------- */

  // Added private(i,x)
# pragma omp parallel for private(i,x)
  for (i=1; i<N; i++){
    x = sqrt(b[i]) - 1;
    a[i] = x*x + 2*x + 1;
  } /* end of omp parallel for */

  /* testing the correctness of the numerical result: */
  sum=0; for (i=1; i<N; i++) { sum = sum + a[i]; }
  /* sum_expected = same as in Exa.2 */
  printf("Exa.3: sum  computed=%8.1f,  expected=%8.1f,  difference=%8.5f \n",
                                 sum,  sum_expected, sum-sum_expected);

  /* Example 4 (this example contains an OpenMP parallelization error) */
  /* --------- */

  f = 2;
  // Added lastprivate(x) firstprivate(f)
# pragma omp parallel for lastprivate(x) firstprivate(f)
  for (i=1; i<N; i++){
    x = f * b[i];
    a[i] = x - 7;
  } /* end of omp parallel for */
  a[0] = x;

  /* testing the correctness of the numerical result: */
  printf("Exa.4: a[0] computed=%8.1f,  expected=%8.1f,  difference=%8.5f \n",
                                a[0],        2*b[N-1],   a[0] - 2*b[N-1] );


  /* Example 5 (this example contains an OpenMP parallelization error) */
  /* --------- */

  sum = 0;
  // Added reduction(+:sum)
# pragma omp parallel for reduction(+:sum)
  for (i=1; i<N; i++){
    sum = sum + b[i];
  } /* end of omp parallel for */

  /* testing the correctness of the numerical result: */
  /* sum_expected = same as in Exa.2 */
  printf("Exa.5: sum  computed=%8.1f,  expected=%8.1f,  difference=%8.5f \n",
                                 sum,  sum_expected, sum-sum_expected);

}