.TH CHEGS2 l "15 June 2000" "LAPACK version 3.0" ")"
.SH NAME
CHEGS2 - reduce a complex Hermitian-definite generalized eigenproblem to standard form
.SH SYNOPSIS
.TP 19
SUBROUTINE CHEGS2(
ITYPE, UPLO, N, A, LDA, B, LDB, INFO )
.TP 19
.ti +4
CHARACTER
UPLO
.TP 19
.ti +4
INTEGER
INFO, ITYPE, LDA, LDB, N
.TP 19
.ti +4
COMPLEX
A( LDA, * ), B( LDB, * )
.SH PURPOSE
CHEGS2 reduces a complex Hermitian-definite generalized eigenproblem to standard form. 
If ITYPE = 1, the problem is A*x = lambda*B*x,
.br
and A is overwritten by inv(U')*A*inv(U) or inv(L)*A*inv(L')

If ITYPE = 2 or 3, the problem is A*B*x = lambda*x or
.br
B*A*x = lambda*x, and A is overwritten by U*A*U` or L'*A*L.

B must have been previously factorized as U'*U or L*L' by CPOTRF.

.SH ARGUMENTS
.TP 8
ITYPE   (input) INTEGER
= 1: compute inv(U')*A*inv(U) or inv(L)*A*inv(L');
.br
= 2 or 3: compute U*A*U' or L'*A*L.
.TP 8
UPLO    (input) CHARACTER
Specifies whether the upper or lower triangular part of the
Hermitian matrix A is stored, and how B has been factorized.
= 'U':  Upper triangular
.br
= 'L':  Lower triangular
.TP 8
N       (input) INTEGER
The order of the matrices A and B.  N >= 0.
.TP 8
A       (input/output) COMPLEX array, dimension (LDA,N)
On entry, the Hermitian matrix A.  If UPLO = 'U', the leading
n by n upper triangular part of A contains the upper
triangular part of the matrix A, and the strictly lower
triangular part of A is not referenced.  If UPLO = 'L', the
leading n by n lower triangular part of A contains the lower
triangular part of the matrix A, and the strictly upper
triangular part of A is not referenced.

On exit, if INFO = 0, the transformed matrix, stored in the
same format as A.
.TP 8
LDA     (input) INTEGER
The leading dimension of the array A.  LDA >= max(1,N).
.TP 8
B       (input) COMPLEX array, dimension (LDB,N)
The triangular factor from the Cholesky factorization of B,
as returned by CPOTRF.
.TP 8
LDB     (input) INTEGER
The leading dimension of the array B.  LDB >= max(1,N).
.TP 8
INFO    (output) INTEGER
= 0:  successful exit.
.br
< 0:  if INFO = -i, the i-th argument had an illegal value.