1CHEGS2(1)                LAPACK routine (version 3.2)                CHEGS2(1)
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NAME

6       CHEGS2  - reduces a complex Hermitian-definite generalized eigenproblem
7       to standard form
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SYNOPSIS

10       SUBROUTINE CHEGS2( ITYPE, UPLO, N, A, LDA, B, LDB, INFO )
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12           CHARACTER      UPLO
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14           INTEGER        INFO, ITYPE, LDA, LDB, N
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16           COMPLEX        A( LDA, * ), B( LDB, * )
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PURPOSE

19       CHEGS2 reduces a complex Hermitian-definite generalized eigenproblem to
20       standard form.  If ITYPE = 1, the problem is A*x = lambda*B*x,
21       and A is overwritten by inv(U')*A*inv(U) or inv(L)*A*inv(L') If ITYPE =
22       2 or 3, the problem is A*B*x = lambda*x or
23       B*A*x = lambda*x, and A is overwritten by U*A*U`  or  L'*A*L.   B  must
24       have been previously factorized as U'*U or L*L' by CPOTRF.
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ARGUMENTS

27       ITYPE   (input) INTEGER
28               = 1: compute inv(U')*A*inv(U) or inv(L)*A*inv(L');
29               = 2 or 3: compute U*A*U' or L'*A*L.
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31       UPLO    (input) CHARACTER*1
32               Specifies  whether  the  upper  or lower triangular part of the
33               Hermitian matrix A is stored, and how B has been factorized.  =
34               'U':  Upper triangular
35               = 'L':  Lower triangular
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37       N       (input) INTEGER
38               The order of the matrices A and B.  N >= 0.
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40       A       (input/output) COMPLEX array, dimension (LDA,N)
41               On entry, the Hermitian matrix A.  If UPLO = 'U', the leading n
42               by n upper triangular part of A contains the  upper  triangular
43               part of the matrix A, and the strictly lower triangular part of
44               A is not referenced.  If UPLO = 'L', the leading n by  n  lower
45               triangular  part of A contains the lower triangular part of the
46               matrix A, and the strictly upper triangular part of  A  is  not
47               referenced.   On  exit,  if  INFO  = 0, the transformed matrix,
48               stored in the same format as A.
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50       LDA     (input) INTEGER
51               The leading dimension of the array A.  LDA >= max(1,N).
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53       B       (input) COMPLEX array, dimension (LDB,N)
54               The triangular factor from the Cholesky factorization of B,  as
55               returned by CPOTRF.
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57       LDB     (input) INTEGER
58               The leading dimension of the array B.  LDB >= max(1,N).
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60       INFO    (output) INTEGER
61               = 0:  successful exit.
62               < 0:  if INFO = -i, the i-th argument had an illegal value.
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66 LAPACK routine (version 3.2)    November 2008                       CHEGS2(1)
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