```/* nag_dsytri (f07mjc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.1, 2017.
*/

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf07.h>
#include <nagx04.h>

int main(void)
{
/* Scalars */
Integer i, j, n, pda;
Integer exit_status = 0;
Nag_UploType uplo;
Nag_MatrixType matrix;
NagError fail;
Nag_OrderType order;
/* Arrays */
char nag_enum_arg[40];
Integer *ipiv = 0;
double *a = 0;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J-1)*pda + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I-1)*pda + J - 1]
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_dsytri (f07mjc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
pda = n;
#else
pda = n;
#endif

/* Allocate memory */
if (!(ipiv = NAG_ALLOC(n, Integer)) || !(a = NAG_ALLOC(n * n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read A from data file */
scanf(" %39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
uplo = (Nag_UploType) nag_enum_name_to_value(nag_enum_arg);

if (uplo == Nag_Upper) {
matrix = Nag_UpperMatrix;
for (i = 1; i <= n; ++i) {
for (j = i; j <= n; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
}
else {
matrix = Nag_LowerMatrix;
for (i = 1; i <= n; ++i) {
for (j = 1; j <= i; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
}

/* Factorize A */
/* nag_dsytrf (f07mdc).
* Bunch-Kaufman factorization of real symmetric indefinite
* matrix
*/
nag_dsytrf(order, uplo, n, a, pda, ipiv, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dsytrf (f07mdc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Compute inverse of A */
/* nag_dsytri (f07mjc).
* Inverse of real symmetric indefinite matrix, matrix
* already factorized by nag_dsytrf (f07mdc)
*/
nag_dsytri(order, uplo, n, a, pda, ipiv, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dsytri (f07mjc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print inverse */
/* nag_gen_real_mat_print (x04cac).
* Print real general matrix (easy-to-use)
*/
fflush(stdout);
nag_gen_real_mat_print(order, matrix, Nag_NonUnitDiag, n, n, a, pda,
"Inverse", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
END:
NAG_FREE(ipiv);
NAG_FREE(a);
return exit_status;
}
```