/* nag_dsyevx (f08fbc) Example Program.
*
* Copyright 2014 Numerical Algorithms Group.
*
* Mark 23, 2011.
*/

#include <stdio.h>
#include <nag.h>
#include <nag_stdlib.h>
#include <nagf08.h>
#include <nagx04.h>

int main(void)
{
/* Scalars */
double        abstol, vl, vu;
Integer       i, il = 0, iu = 0, j, m, n, pda, pdz;
Integer       exit_status = 0;
/* Arrays */
char          nag_enum_arg[40];
double        *a = 0, *w = 0, *z = 0;
Integer       *index = 0;
/* Nag Types */
Nag_OrderType order;
Nag_RangeType range;
Nag_UploType  uplo;
Nag_JobType   job;
NagError      fail, fail_print;

#ifdef NAG_COLUMN_MAJOR
#define A(I, J) a[(J - 1) * pda + I - 1]
#define Z(I, J) z[(J - 1) * pdz + I - 1]
order = Nag_ColMajor;
#else
#define A(I, J) a[(I - 1) * pda + J - 1]
#define Z(I, J) z[(I - 1) * pdz + J - 1]
order = Nag_RowMajor;
#endif

INIT_FAIL(fail);

printf("nag_dsyevx (f08fbc) Example Program Results\n\n");

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

/* Read uplo, range and job */
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);
scanf("%39s%*[^\n]", nag_enum_arg);
range = (Nag_RangeType) nag_enum_name_to_value(nag_enum_arg);
scanf("%39s%*[^\n]", nag_enum_arg);
job = (Nag_JobType) nag_enum_name_to_value(nag_enum_arg);

/* Allocate memory */
if (!(a = NAG_ALLOC(n*n, double)) ||
!(w = NAG_ALLOC(n, double)) ||
!(z = NAG_ALLOC(n*n, double)) ||
!(index = NAG_ALLOC(n, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

pda = n;
pdz = n;

/* Read the lower and upper bounds of the interval to be searched,
* and read the upper triangular part of the matrix A from data file
*/
scanf("%lf%lf%*[^\n]", &vl, &vu);
for (i = 1; i <= n; ++i)
for (j = i; j <= n; ++j)
scanf("%lf", &A(i, j));
scanf("%*[^\n]");

/* Set the absolute error tolerance for eigenvalues. With abstol
* set to zero, the default value is used instead.
*/
abstol = 0.0;

/* nag_dsyevx (f08fbc).
* Solve the symmetric eigenvalue problem.
*/
nag_dsyevx(order, job, range, uplo, n, a, pda, vl, vu, il, iu, abstol, &m,
w, z, pdz, index, &fail);
if (fail.code != NE_NOERROR && fail.code != NE_CONVERGENCE)
{
printf("Error from nag_dsyevx (f08fbc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Normalize the eigenvectors */
for(j=1; j<=m; j++)
for(i=n; i>=1; i--)
Z(i, j) = Z(i, j) / Z(1,j);

/* Print solution */
printf("Number of eigenvalues found =%5ld\n", m);

printf("\nEigenvalues\n");
for (j = 0; j < m; ++j)
printf("%8.4f%s", w[j], (j+1)%8 == 0?"\n":" ");
printf("\n\n");

/* nag_gen_real_mat_print (x04cac).
* Print selected eigenvectors.
*/
INIT_FAIL(fail_print);
fflush(stdout);
nag_gen_real_mat_print(order, Nag_GeneralMatrix, Nag_NonUnitDiag, n, m, z,
pdz, "Selected eigenvectors", 0, &fail_print);
if (fail_print.code != NE_NOERROR)
{
printf("Error from nag_gen_real_mat_print (x04cac).\n%s\n",
fail_print.message);
exit_status = 1;
goto END;
}
if (fail.code == NE_CONVERGENCE)
{
printf("eigenvectors failed to converge\n");
printf("Indices of eigenvectors that did not converge\n");
for (j = 0; j < m; ++j)
printf("%8ld%s", index[j], (j+1)%8 == 0?"\n":" ");
}

END:
NAG_FREE(a);
NAG_FREE(w);
NAG_FREE(z);
NAG_FREE(index);

return exit_status;
}

#undef A
#undef Z