NAG Library Manual, Mark 28.5
```/* nag_blast_dgemm (f16yac) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.5, 2022.
*/

#include <nag.h>
#include <stdio.h>

int main(void) {

/* Scalars */
double alpha, beta;
Integer exit_status, i, j, k, m, n, pda, pdb, pdc;

/* Arrays */
double *a = 0, *b = 0, *c = 0;
char nag_enum_arg[40];

/* Nag Types */
NagError fail;
Nag_OrderType order;
Nag_TransType transa;
Nag_TransType transb;

#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]
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]
order = Nag_RowMajor;
#endif

exit_status = 0;
INIT_FAIL(fail);

printf("nag_blast_dgemm (f16yac) Example Program Results\n\n");

/* Skip heading in data file */
scanf("%*[^\n] ");

/* Read the problem dimensions */
scanf("%" NAG_IFMT "%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &m, &n, &k);

/* Read the transpose parameters */
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
transa = (Nag_TransType)nag_enum_name_to_value(nag_enum_arg);
scanf("%39s%*[^\n] ", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
transb = (Nag_TransType)nag_enum_name_to_value(nag_enum_arg);
scanf("%lf%lf%*[^\n] ", &alpha, &beta);

#ifdef NAG_COLUMN_MAJOR
pdc = m;
if (transa == Nag_NoTrans && transb == Nag_NoTrans) {
pda = m;
pdb = k;
} else if ((transa == Nag_Trans || transa == Nag_ConjTrans) &&
transb == Nag_NoTrans) {
pda = k;
pdb = k;
} else if (transa == Nag_NoTrans &&
(transb == Nag_Trans || transb == Nag_ConjTrans)) {
pda = m;
pdb = n;
} else {
pda = k;
pdb = n;
}
#else
pdc = n;
if (transa == Nag_NoTrans && transb == Nag_NoTrans) {
pda = k;
pdb = n;
} else if ((transa == Nag_Trans || transa == Nag_ConjTrans) &&
transb == Nag_NoTrans) {
pda = m;
pdb = n;
} else if (transa == Nag_NoTrans &&
(transb == Nag_Trans || transb == Nag_ConjTrans)) {
pda = k;
pdb = k;
} else {
pda = m;
pdb = k;
}
#endif

if (m > 0 && n > 0) {
/* Allocate memory */
if (!(a = NAG_ALLOC(m * k, double)) || !(b = NAG_ALLOC(n * k, double)) ||
!(c = NAG_ALLOC(m * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
} else {
printf("Invalid m, n or k\n");
exit_status = 1;
return exit_status;
}

/* Input matrix A */
if (transa == Nag_NoTrans) {
for (i = 1; i <= m; ++i) {
for (j = 1; j <= k; ++j)
scanf("%lf", &A(i, j));
scanf("%*[^\n] ");
}
} else {
for (i = 1; i <= k; ++i) {
for (j = 1; j <= m; ++j)
scanf("%lf", &A(i, j));
scanf("%*[^\n] ");
}
}

/* Input matrix B */
if (transb == Nag_NoTrans) {
for (i = 1; i <= k; ++i) {
for (j = 1; j <= n; ++j)
scanf("%lf", &B(i, j));
scanf("%*[^\n] ");
}
} else {
for (i = 1; i <= n; ++i) {
for (j = 1; j <= k; ++j)
scanf("%lf", &B(i, j));
scanf("%*[^\n] ");
}
}

/* Input matrix C */
for (i = 1; i <= m; ++i) {
for (j = 1; j <= n; ++j)
scanf("%lf", &C(i, j));
scanf("%*[^\n] ");
}

/* nag_blast_dgemm (f16yac).
* Matrix-matrix multiply.
*
*/
nag_blast_dgemm(order, transa, transb, m, n, k, alpha, a, pda, b, pdb, beta,
c, pdc, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_blast_dgemm.\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print result */
/* nag_file_print_matrix_real_gen (x04cac).
* Print real general matrix (easy-to-use)
*/
fflush(stdout);
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, m,
n, c, pdc, "Matrix Matrix Product", 0, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_file_print_matrix_real_gen (x04cac).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

END:
NAG_FREE(a);
NAG_FREE(b);
NAG_FREE(c);

return exit_status;
}
```