```/* nag_dtrsyl (f08qhc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.2, 2017.
*/

#include <stdio.h>
#include <math.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf08.h>
#include <nagf16.h>
#include <nagx04.h>
#include <nagx02.h>

int main(void)
{
/* Scalars */
Integer i, j, m, n, pda, pdb, pdc, pdd, pde, pdf;
Integer exit_status = 0;
double alpha, beta, norm, scale;
Nag_SignType sign = Nag_Minus;
NagError fail;
Nag_OrderType order;
/* Arrays */
double *a = 0, *b = 0, *c = 0, *d = 0, *e = 0, *f = 0;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J-1)*pda + I - 1]
#define B(I, J) b[(J-1)*pdb + I - 1]
#define C(I, J) c[(J-1)*pdc + I - 1]
#define D(I, J) d[(J-1)*pdd + I - 1]
#define E(I, J) e[(J-1)*pde + I - 1]
#define F(I, J) f[(J-1)*pdf + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I-1)*pda + J - 1]
#define B(I, J) b[(I-1)*pdb + J - 1]
#define C(I, J) c[(I-1)*pdc + J - 1]
#define D(I, J) d[(I-1)*pdd + J - 1]
#define E(I, J) e[(I-1)*pde + J - 1]
#define F(I, J) f[(I-1)*pdf + J - 1]
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_dtrsyl (f08qhc) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &m, &n);
#ifdef NAG_COLUMN_MAJOR
pda = m;
pdb = n;
pdc = m;
pdd = m;
pde = m;
pdf = m;
#else
pda = m;
pdb = n;
pdc = n;
pdd = n;
pde = n;
pdf = n;
#endif

/* Allocate memory */
if (!(a = NAG_ALLOC(m * m, double)) ||
!(b = NAG_ALLOC(n * m, double)) ||
!(c = NAG_ALLOC(m * n, double)) ||
!(d = NAG_ALLOC(m * n, double)) ||
!(e = NAG_ALLOC(m * n, double)) || !(f = NAG_ALLOC(m * n, double))
)
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read A, B and C from data file */
for (i = 1; i <= m; ++i) {
for (j = 1; j <= m; ++j)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n] ");
for (i = 1; i <= n; ++i) {
for (j = 1; j <= n; ++j)
scanf("%lf", &B(i, j));
}
scanf("%*[^\n] ");
for (i = 1; i <= m; ++i) {
for (j = 1; j <= n; ++j)
scanf("%lf", &C(i, j));
}
scanf("%*[^\n] ");

/* Copy C into F */
for (i = 1; i <= m; ++i) {
for (j = 1; j <= m; ++j)
F(i, j) = C(i, j);
}

/* nag_gen_real_mat_print (x04cac): Print Matrix C. */
fflush(stdout);
nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, m, n,
c, pdc, "Matrix C", 0, &fail);
printf("\n");
if (fail.code != NE_NOERROR) {
printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Reorder the Schur factorization T */
/* nag_dtrsyl (f08qhc).
* Solve real Sylvester matrix equation AX + XB = C, A and B
* are upper quasi-triangular or transposes
*/
nag_dtrsyl(order, Nag_NoTrans, Nag_NoTrans, sign, m, n, a, pda,
b, pdb, c, pdc, &scale, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dtrsyl (f08qhc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* nag_dgemm (f16yac): Compute aC - (A*X + X*B*sign) from solution */
/* and store in matrix E */
alpha = 1.0;
beta = 0.0;
nag_dgemm(order, Nag_NoTrans, Nag_NoTrans, m, n, m, alpha, a, pda,
c, pdc, beta, d, pdd, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dgemm (f16yac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
if (sign == Nag_Minus)
alpha = -1.0;
else
alpha = 1.0;
beta = 1.0;
nag_dgemm(order, Nag_NoTrans, Nag_NoTrans, m, n, n, alpha, c, pdc, b,
pdb, beta, d, pdd, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dgemm (f16yac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
for (i = 1; i <= m; i++) {
for (j = 1; j <= n; j++)
E(i, j) = scale * F(i, j) - D(i, j);
}

/* nag_dge_norm (f16rac): Find norm of matrix E and print warning if */
/* it is too large */
nag_dge_norm(order, Nag_OneNorm, n, n, e, pde, &norm, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_dge_norm (f16rac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
if (norm > pow(x02ajc(), 0.8)) {
printf("%s\n%s\n",
"Norm of aC - (A*X + X*B*sign) is much greater than 0.",
"nag_dtrsyl (f08qhc) has failed.");
}
else {
printf(" SCALE = %11.2e\n", scale);
}
END:
NAG_FREE(a);
NAG_FREE(b);
NAG_FREE(c);
NAG_FREE(d);
NAG_FREE(e);
NAG_FREE(f);

return exit_status;
}
```