```/* nag_nearest_correlation (g02aac) Example Program.
*
* Copyright 2014 Numerical Algorithms Group.
*
* Mark 9, 2009.
*/
/* Pre-processor includes */
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagg02.h>

int main(void)
{
/*Integer scalar and array declarations */
Integer       exit_status = 0;
Integer       feval, i, iter, j, maxit, maxits, n;
Integer       ldg, pdg, pdx;
/*Double scalar and array declarations */
double        errtol, nrmgrd;
double        *g = 0, *x = 0;
Nag_OrderType order;
NagError      fail;

INIT_FAIL(fail);

printf("%s\n",
"nag_nearest_correlation (g02aac) Example Program Results");
printf("\n");
n = 4;
ldg = 5;
#ifdef NAG_COLUMN_MAJOR
pdg = ldg;
#define G(I, J) g[(J-1)*pdg + I-1]
pdx = n;
#define X(I, J) x[(J-1)*pdx + I-1]
order = Nag_ColMajor;
#else
pdg = n;
#define G(I, J) g[(I-1)*pdg + J-1]
pdx = n;
#define X(I, J) x[(I-1)*pdx + J-1]
order = Nag_RowMajor;
#endif
if (!(g = NAG_ALLOC(ldg*n, double)) ||
!(x = NAG_ALLOC(n*n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Set up matrix G*/
for (j = 1; j <= n; j++)
{
for (i = 1; i <= n; i++)
G(i, j) = 0.0;
G(j, j) = 2.00e0;
}
for (j = 2; j <= n; j++)
{
G(j-1, j) = (-(1.00e0));
G(j, j-1) = (-(1.00e0));
}
/* Set up method parameters*/
errtol = 1.00e-7;
maxits = 200;
maxit = 10;
/*
* nag_nearest_correlation (g02aac)
* Computes the nearest correlation matrix to a real square matrix,
* using the method of Qi and Sun
*/
nag_nearest_correlation(order, g, pdg, n, errtol, maxits, maxit, x, pdx,
&iter, &feval, &nrmgrd, &fail);
if (fail.code != NE_NOERROR)
{
printf("Error from nag_nearest_correlation (g02aac).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
printf("%s\n", "     Nearest Correlation Matrix");
for (i = 1; i <= n; i++)
{
for (j = 1; j <= n; j++)
printf("%11.5f%s", X(i, j), j%4?" ":"\n");
}
printf("\n");
printf("\n");
printf("%s%11ld\n", " Number of Newton steps taken:", iter);
printf("%s%9ld\n", " Number of function evaluations:", feval);
if (nrmgrd > errtol)
printf("%s %12.3e\n", " Norm of gradient of last Newton step:",
nrmgrd);
printf("\n");

END:
NAG_FREE(g);
NAG_FREE(x);

return exit_status;
}
```