ZHPGST - reduce a complex Hermitian-definite generalized
eigenproblem to standard form, using packed storage
SYNOPSIS
SUBROUTINE ZHPGST( ITYPE, UPLO, N, AP, BP, INFO )
CHARACTER UPLO
INTEGER INFO, ITYPE, N
COMPLEX*16 AP( * ), BP( * )
PURPOSE
ZHPGST 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 ZPPTRF.
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*16 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.
The triangular factor from the Cholesky factoriza
tion of B, stored in the same format as A, as
returned by ZPPTRF.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille
gal value
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