f08tsce.c

/* nag_lapackeig_zhpgst (f08tsc) Example Program.
 *
 * Copyright 2025 Numerical Algorithms Group.
 *
 * Mark 31.1, 2025.
 */
#include<nag.h>
#include<stdio.h>
intmain(void){
/* Scalars */
Integeri,j,n,ap_len,bp_len,d_len,e_len,tau_len;
Integerexit_status=0;
NagErrorfail;
Nag_UploTypeuplo;
Nag_OrderTypeorder;
/* Arrays */
charnag_enum_arg[40];
Complex*ap=0,*bp=0,*tau=0;
double*d=0,*e=0;
#ifdef NAG_COLUMN_MAJOR
#define A_UPPER(I, J) ap[J * (J - 1) / 2 + I - 1]
#define A_LOWER(I, J) ap[(2 * n - J) * (J - 1) / 2 + I - 1]
#define B_UPPER(I, J) bp[J * (J - 1) / 2 + I - 1]
#define B_LOWER(I, J) bp[(2 * n - J) * (J - 1) / 2 + I - 1]
order=Nag_ColMajor;
#else
#define A_LOWER(I, J) ap[I * (I - 1) / 2 + J - 1]
#define A_UPPER(I, J) ap[(2 * n - I) * (I - 1) / 2 + J - 1]
#define B_LOWER(I, J) bp[I * (I - 1) / 2 + J - 1]
#define B_UPPER(I, J) bp[(2 * n - I) * (I - 1) / 2 + J - 1]
order=Nag_RowMajor;
#endif
INIT_FAIL(fail);
printf("nag_lapackeig_zhpgst (f08tsc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%"NAG_IFMT"%*[^\n] ",&n);
ap_len=n*(n+1)/2;
bp_len=n*(n+1)/2;
d_len=n;
e_len=n-1;
tau_len=n;
/* Allocate memory */
if(!(ap=NAG_ALLOC(ap_len,Complex))||
!(bp=NAG_ALLOC(bp_len,Complex))||!(d=NAG_ALLOC(d_len,double))||
!(e=NAG_ALLOC(e_len,double))||!(tau=NAG_ALLOC(tau_len,Complex))){
printf("Allocation failure\n");
exit_status=-1;
gotoEND;
}
/* Read A and B from data file */
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);
if(uplo==Nag_Upper){
for(i=1;i<=n;++i){
for(j=i;j<=n;++j){
scanf(" ( %lf , %lf )",&A_UPPER(i,j).re,&A_UPPER(i,j).im);
}
}
scanf("%*[^\n] ");
for(i=1;i<=n;++i){
for(j=i;j<=n;++j){
scanf(" ( %lf , %lf )",&B_UPPER(i,j).re,&B_UPPER(i,j).im);
}
}
scanf("%*[^\n] ");
}else{
for(i=1;i<=n;++i){
for(j=1;j<=i;++j){
scanf(" ( %lf , %lf )",&A_LOWER(i,j).re,&A_LOWER(i,j).im);
}
}
scanf("%*[^\n] ");
for(i=1;i<=n;++i){
for(j=1;j<=i;++j){
scanf(" ( %lf , %lf )",&B_LOWER(i,j).re,&B_LOWER(i,j).im);
}
}
scanf("%*[^\n] ");
}
/* Compute the Cholesky factorization of B */
/* nag_lapacklin_zpptrf (f07grc).
 * Cholesky factorization of complex Hermitian
 * positive-definite matrix, packed storage
 */
nag_lapacklin_zpptrf(order,uplo,n,bp,&fail);
if(fail.code!=NE_NOERROR){
printf("Error from nag_lapacklin_dpptrf (f07gdc).\n%s\n",fail.message);
exit_status=1;
gotoEND;
}
/* Reduce the problem to standard form C*y = lambda*y, storing */
/* the result in A */
/* nag_lapackeig_zhpgst (f08tsc).
 * Reduction to standard form of complex Hermitian-definite
 * generalized eigenproblem Ax = lambda Bx, ABx = lambda x
 * or BAx = lambda x, packed storage, B factorized by
 * nag_lapacklin_zpptrf (f07grc)
 */
nag_lapackeig_zhpgst(order,Nag_Compute_1,uplo,n,ap,bp,&fail);
if(fail.code!=NE_NOERROR){
printf("Error from nag_lapackeig_zhpgst (f08tsc).\n%s\n",fail.message);
exit_status=1;
gotoEND;
}
/* Reduce C to tridiagonal form T = (Q^T)*C*Q */
/* nag_lapackeig_zhptrd (f08gsc).
 * Unitary reduction of complex Hermitian matrix to real
 * symmetric tridiagonal form, packed storage
 */
nag_lapackeig_zhptrd(order,uplo,n,ap,d,e,tau,&fail);
if(fail.code!=NE_NOERROR){
printf("Error from nag_lapackeig_zhptrd (f08gsc).\n%s\n",fail.message);
exit_status=1;
gotoEND;
}
/* Calculate the eigenvalues of T (same as C) */
/* nag_lapackeig_dsterf (f08jfc).
 * All eigenvalues of real symmetric tridiagonal matrix,
 * root-free variant of QL or QR
 */
nag_lapackeig_dsterf(n,d,e,&fail);
if(fail.code!=NE_NOERROR){
printf("Error from nag_lapackeig_dsterf (f08jfc).\n%s\n",fail.message);
exit_status=1;
gotoEND;
}
/* Print eigenvalues */
printf("Eigenvalues\n");
for(i=1;i<=n;++i)
printf("%8.4f%s",d[i-1],i%9==0||i==n?"\n":" ");
printf("\n");
END:
NAG_FREE(ap);
NAG_FREE(bp);
NAG_FREE(d);
NAG_FREE(e);
NAG_FREE(tau);
returnexit_status;
}