source: CIVL/examples/omp/DataRaceBench/micro-benchmarks/jacobikernel-orig-no.c@ e5cec5ae

// Two parallel for loops within one single parallel region,
// combined with private() and reduction().
#include <stdio.h>
#include <math.h>

#define MSIZE 200
int n=MSIZE, m=MSIZE, mits=1000;
double tol=0.0000000001, relax = 1.0, alpha = 0.0543;
double u[MSIZE][MSIZE], f[MSIZE][MSIZE], uold[MSIZE][MSIZE];
double dx, dy;

void
initialize ()
{
  int i, j, xx, yy;

  dx = 2.0 / (n - 1); // -->dx@112:2
  dy = 2.0 / (m - 1);  //-->dy@113:2

  /* Initialize initial condition and RHS */
//#pragma omp parallel for private(i,j,xx,yy)
  for (i = 0; i < n; i++)
    for (j = 0; j < m; j++)
    {
      xx = (int) (-1.0 + dx * (i - 1));       /* -1 < x < 1 */
      yy = (int) (-1.0 + dy * (j - 1));       /* -1 < y < 1 */
      u[i][j] = 0.0;
      f[i][j] = -1.0 * alpha * (1.0 - xx * xx) * (1.0 - yy * yy)
        - 2.0 * (1.0 - xx * xx) - 2.0 * (1.0 - yy * yy);

    }
}

void
jacobi ()
{
  double omega;
  int i, j, k;
  double error, resid,  ax, ay, b;

  omega = relax;
/*
* Initialize coefficients */

  dx = 2.0 / (n - 1); // -->dx@112:2
  dy = 2.0 / (m - 1);  //-->dy@113:2

  ax = 1.0 / (dx * dx);         /* X-direction coef */
  ay = 1.0 / (dy * dy);         /* Y-direction coef */
  b = -2.0 / (dx * dx) - 2.0 / (dy * dy) - alpha;       /* Central coeff */

  error = 10.0 * tol;
  k = 1;

  while (k <= mits)
    {
      error = 0.0;

/* Copy new solution into old */
#pragma omp parallel
      {
#pragma omp for private(i,j)
        for (i = 0; i < n; i++)
          for (j = 0; j < m; j++)
            uold[i][j] = u[i][j];
#pragma omp for private(i,j,resid) reduction(+:error) nowait
        for (i = 1; i < (n - 1); i++)
          for (j = 1; j < (m - 1); j++)
            {
              resid = (ax * (uold[i - 1][j] + uold[i + 1][j])
                       + ay * (uold[i][j - 1] + uold[i][j + 1]) +
                       b * uold[i][j] - f[i][j]) / b;

              u[i][j] = uold[i][j] - omega * resid;
              error = error + resid * resid;
            }
      }
/*  omp end parallel */

/* Error check */

     k = k + 1;
      error = sqrt (error) / (n * m);
    }                           /*  End iteration loop */

  printf ("Total Number of Iterations:%d\n", k);
  printf ("Residual:%E\n", error);
}

int main()
{
  initialize();
  jacobi();
  return 0;
}