/* nag_lapackeig_dgesvj (f08kjc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.3, 2022.
*/
#include <math.h>
#include <nag.h>
#include <stdio.h>
int main(void) {
/* Scalars */
double eps, serrbd, ctol;
Integer exit_status = 0;
Integer i, j, lwork, m, mv, n, n_vrows, n_vcols, pda, pdv, ranka;
/* Arrays */
double *a = 0, *rcondu = 0, *rcondv = 0, *s = 0, *v = 0, *work = 0;
char nag_enum_arg[40];
/* Nag Types */
Nag_OrderType order;
Nag_MatrixType joba;
Nag_LeftVecsType jobu;
Nag_RightVecsType jobv;
NagError fail;
#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
#define V(I, J) v[(J - 1) * pdv + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
#define V(I, J) v[(I - 1) * pdv + J - 1]
order = Nag_RowMajor;
#endif
INIT_FAIL(fail);
printf("nag_lapackeig_dgesvj (f08kjc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &m, &n);
if (n < 0 || m < n) {
printf("Invalid m or n\n");
exit_status = 1;
goto END;
;
}
/* Read Nag type arguments by name and convert to value */
scanf(" %39s%*[^\n]", nag_enum_arg);
/* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
joba = (Nag_MatrixType)nag_enum_name_to_value(nag_enum_arg);
scanf(" %39s%*[^\n]", nag_enum_arg);
jobu = (Nag_LeftVecsType)nag_enum_name_to_value(nag_enum_arg);
scanf(" %39s%*[^\n]", nag_enum_arg);
jobv = (Nag_RightVecsType)nag_enum_name_to_value(nag_enum_arg);
scanf(" %39s%*[^\n]", nag_enum_arg);
n_vcols = n;
n_vrows = n;
mv = 0;
if (jobv == Nag_RightVecsMV) {
scanf("%" NAG_IFMT, &mv);
n_vrows = mv;
} else if (jobv == Nag_NotRightVecs) {
n_vrows = 1;
n_vcols = 1;
}
scanf("%*[^\n]");
#ifdef NAG_COLUMN_MAJOR
pda = m;
pdv = n_vrows;
#else
pda = n;
pdv = n_vcols;
#endif
lwork = 6;
if (!(a = NAG_ALLOC(m * n, double)) || !(rcondu = NAG_ALLOC(m, double)) ||
!(rcondv = NAG_ALLOC(m, double)) || !(s = NAG_ALLOC(n, double)) ||
!(v = NAG_ALLOC(n_vrows * n_vcols, double)) ||
!(work = NAG_ALLOC(lwork, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
/* Read the m by n matrix A from data file */
if (joba == Nag_GeneralMatrix) {
for (i = 1; i <= m; i++)
for (j = 1; j <= n; j++)
scanf("%lf", &A(i, j));
} else if (joba == Nag_UpperMatrix) {
for (i = 1; i <= m; i++)
for (j = i; j <= n; j++)
scanf("%lf", &A(i, j));
} else {
for (i = 1; i <= m; i++)
for (j = 1; j <= i; j++)
scanf("%lf", &A(i, j));
}
scanf("%*[^\n]");
/* jobv==Nag_RightVecsMV means that the first mv rows of v must be set. */
if (jobv == Nag_RightVecsMV) {
for (i = 1; i <= mv; i++)
for (j = 1; j <= n; j++)
scanf("%lf", &V(i, j));
scanf("%*[^\n]");
}
ctol = 10.0;
/* nag_lapackeig_dgesvj (f08kjc)
* Compute the singular values and left and right singular vectors
* of A (A = U*S*V, m>=n).
*/
nag_lapackeig_dgesvj(order, joba, jobu, jobv, m, n, a, pda, s, mv, v, pdv,
ctol, work, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapackeig_dgesvj (f08kjc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Get the machine precision, eps and compute the approximate
* error bound for the computed singular values. Note that for
* the 2-norm, s[0] = norm(A).
*/
eps = nag_machine_precision;
serrbd = eps * s[0];
/* Print solution */
printf("Singular values\n ");
for (j = 0; j < n; j++)
printf("%8.4f", s[j]);
printf("\n\n");
if (fabs(work[0] - 1.0) > eps)
printf("Values need scaling by factor = %13.5e\n\n", work[0]);
ranka = (Integer)work[1];
printf("Rank of A = %5" NAG_IFMT "\n\n", ranka);
if (jobu != Nag_NotLeftVecs) {
/* 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,
ranka, a, pda,
"Left spanning singular vectors", 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;
}
}
if (jobv == Nag_RightVecs) {
printf("\n");
fflush(stdout);
nag_file_print_matrix_real_gen(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n,
n, v, pdv, "Right singular vectors", 0,
&fail);
} else if (jobv == Nag_RightVecsMV) {
printf("\n");
fflush(stdout);
nag_file_print_matrix_real_gen(
order, Nag_GeneralMatrix, Nag_NonUnitDiag, mv, n, v, pdv,
"Right singular vectors applied to input V", 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;
}
/* nag_lapackeig_ddisna (f08flc)
* Estimate reciprocal condition numbers for the singular vectors.
*/
nag_lapackeig_ddisna(Nag_LeftSingVecs, m, n, s, rcondu, &fail);
nag_lapackeig_ddisna(Nag_RightSingVecs, m, n, s, rcondv, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapackeig_ddisna (f08flc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Print the approximate error bounds for the singular values and vectors. */
printf("\nError estimate for the singular values\n");
printf("%11.1e", serrbd);
printf("\n\nError estimates for left singular vectors\n");
for (i = 0; i < n; i++)
printf("%11.1e", serrbd / rcondu[i]);
printf("\n\nError estimates for right singular vectors\n");
for (i = 0; i < n; i++)
printf("%11.1e", serrbd / rcondv[i]);
printf("\n");
END:
NAG_FREE(a);
NAG_FREE(rcondu);
NAG_FREE(rcondv);
NAG_FREE(s);
NAG_FREE(v);
NAG_FREE(work);
return exit_status;
}