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## chpgst()

subroutine chpgst | ( | integer | itype,
|  | character | uplo,
|  | integer | n,
|  | complex, dimension( * ) | ap,
|  | complex, dimension( * ) | bp,
|  | integer | info )

CHPGST

Download CHPGST + dependencies [TGZ] [ZIP] [TXT]

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.
      !>

Parameters

  [in]

  ITYPE

      !>          ITYPE is 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.
      !>

  [in]

  UPLO

      !>          UPLO is CHARACTER*1
      !>          = '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.
      !>

  [in]

  N

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

  [in,out]

  AP

      !>          AP is COMPLEX array, dimension (N*(N+1)/2)
      !>          On entry, the upper or lower triangle of the Hermitian 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.
      !>

  [in]

  BP

      !>          BP is COMPLEX array, dimension (N*(N+1)/2)
      !>          The triangular factor from the Cholesky factorization of B,
      !>          stored in the same format as A, as returned by CPPTRF.
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0:  successful exit
      !>          < 0:  if INFO = -i, the i-th argument had an illegal value
      !>

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.