chpgst(3)

NAME

CHPGST - reduce a complex Hermitian-definite generalized

eigenproblem to standard form, using packed storage

SYNOPSIS

SUBROUTINE CHPGST( ITYPE, UPLO, N, AP, BP, INFO )
    CHARACTER      UPLO
    INTEGER        INFO, ITYPE, N
    COMPLEX        AP( * ), BP( * )

PURPOSE

CHPGST reduces a complex Hermitian-definite generalized

eigenproblem to standard form, using packed storage. If ITYPE =

1, the problem is A*x = lambda*B*x,
and A is overwritten by inv(U**H)*A*inv(U) or

inv(L)*A*inv(L**H)

If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
B*A*x = lambda*x, and A is overwritten by U*A*U**H or

L**H*A*L.

B must have been previously factorized as U**H*U or L*L**H

by CPPTRF.

ARGUMENTS

ITYPE (input) INTEGER

= 1: compute inv(U**H)*A*inv(U) or

inv(L)*A*inv(L**H);
= 2 or 3: compute U*A*U**H or L**H*A*L.

UPLO (input) CHARACTER

= 'U': Upper triangle of A is stored and B is

factored as U**H*U; = 'L': Lower triangle of A is stored and B

is factored as L*L**H.

N (input) INTEGER

The order of the matrices A and B. N >= 0.

AP (input/output) COMPLEX array, dimension

(N*(N+1)/2)

On entry, the upper or lower triangle of the Her

mitian matrix A, packed columnwise in a linear array. The j-th

column of A is stored in the array AP as follows: if UPLO = 'U',

AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i +

(j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.

On exit, if INFO = 0, the transformed matrix,

stored in the same format as A.

BP (input) COMPLEX array, dimension (N*(N+1)/2)

The triangular factor from the Cholesky factoriza

tion of B, stored in the same format as A, as returned by CPPTRF.

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille

gal value

LAPACK version 3.0 15 June 2000

CHPGST(3)