/* nag_lapackeig_dtrexc (f08qfc) Example Program.
*
* Copyright 2024 Numerical Algorithms Group.
*
* Mark 30.1, 2024.
*/
#include <nag.h>
#include <stdio.h>
int main(void) {
/* Scalars */
Integer i, ifst, ilst, j, n, pdq, pdt;
Integer exit_status = 0;
NagError fail;
Nag_OrderType order;
/* Arrays */
double *q = 0, *t = 0;
#ifdef NAG_COLUMN_MAJOR
#define T(I, J) t[(J - 1) * pdt + I - 1]
order = Nag_ColMajor;
#else
#define T(I, J) t[(I - 1) * pdt + J - 1]
order = Nag_RowMajor;
#endif
INIT_FAIL(fail);
printf("nag_lapackeig_dtrexc (f08qfc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &n);
#ifdef NAG_COLUMN_MAJOR
pdq = 1;
pdt = n;
#else
pdq = 1;
pdt = n;
#endif
/* Allocate memory */
if (!(q = NAG_ALLOC(1 * 1, double)) || !(t = NAG_ALLOC(n * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Read T from data file */
for (i = 1; i <= n; ++i) {
for (j = 1; j <= n; ++j)
scanf("%lf", &T(i, j));
}
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &ifst, &ilst);
/* Reorder the Schur factorization T */
/* nag_lapackeig_dtrexc (f08qfc).
* Reorder Schur factorization of real matrix using
* orthogonal similarity transformation
*/
nag_lapackeig_dtrexc(order, Nag_NotQ, n, t, pdt, q, pdq, &ifst, &ilst, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapackeig_dtrexc (f08qfc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print reordered Schur form */
/* 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, n,
n, t, pdt, "Reordered Schur form", 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(q);
NAG_FREE(t);
return exit_status;
}