/* nag_lapackeig_dbdsqr (f08mec) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.5, 2022.
*/
#include <nag.h>
#include <stdio.h>
int main(void) {
/* Scalars */
Integer i, n, pdvt, pdu;
Integer exit_status = 0, ncc = 0, ldc = 1;
double zero = 0.0, one = 1.0;
/* Arrays */
char nag_enum_arg[40];
double c[1];
double *d = 0, *e = 0, *u = 0, *vt = 0;
/* Nag Types */
NagError fail;
Nag_UploType uplo;
Nag_OrderType order;
INIT_FAIL(fail);
printf("nag_lapackeig_dbdsqr (f08mec) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%*[^\n]", &n);
if (n < 0) {
printf("Invalid n\n");
exit_status = 1;
goto END;
}
#ifdef NAG_COLUMN_MAJOR
order = Nag_ColMajor;
#else
order = Nag_RowMajor;
#endif
pdu = n;
pdvt = n;
/* Allocate memory */
if (!(d = NAG_ALLOC(n, double)) || !(e = NAG_ALLOC(n - 1, double)) ||
!(u = NAG_ALLOC(n * n, double)) || !(vt = NAG_ALLOC(n * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Read B from data file */
for (i = 0; i < n; ++i)
scanf("%lf", &d[i]);
scanf("%*[^\n]");
for (i = 0; i < n - 1; ++i)
scanf("%lf", &e[i]);
scanf("%*[^\n]");
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);
/* Initialize U and VT to be the unit matrix to obtain SVD of input
* bidiagonal matrix nag_blast_dge_load (f16qhc).
* General matrix initialization.
*/
nag_blast_dge_load(order, n, n, zero, one, u, pdu, &fail);
nag_blast_dge_load(order, n, n, zero, one, vt, pdvt, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_blast_dge_load (f16qhc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* nag_lapackeig_dbdsqr (f08mec).
* SVD of real bidiagonal matrix reduced from real general
* matrix.
*/
nag_lapackeig_dbdsqr(order, uplo, n, n, n, ncc, d, e, vt, pdvt, u, pdu, c,
ldc, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapackeig_dbdsqr (f08mec).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print singular values, left & right singular vectors */
printf("\nSingular values\n ");
for (i = 0; i < n; ++i)
printf(" %7.4f%s", d[i], i % 8 == 7 ? "\n" : "");
printf("\n\n");
/* 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, vt, pdvt, "Right singular vectors, by row",
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;
}
printf("\n");
/* nag_file_print_matrix_real_gen (x04cac), see above. */
fflush(stdout);
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
n, u, pdu, "Left singular vectors, by column",
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(d);
NAG_FREE(e);
NAG_FREE(u);
NAG_FREE(vt);
return exit_status;
}