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## zpptri()

subroutine zpptri | ( | character | uplo,
|  | integer | n,
|  | complex*16, dimension( * ) | ap,
|  | integer | info )

ZPPTRI

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

Purpose:

      !>
      !> ZPPTRI computes the inverse of a complex Hermitian positive definite
      !> matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
      !> computed by ZPPTRF.
      !>

Parameters

  [in]

  UPLO

      !>          UPLO is CHARACTER*1
      !>          = 'U':  Upper triangular factor is stored in AP;
      !>          = 'L':  Lower triangular factor is stored in AP.
      !>

  [in]

  N

      !>          N is INTEGER
      !>          The order of the matrix A.  N >= 0.
      !>

  [in,out]

  AP

      !>          AP is COMPLEX*16 array, dimension (N*(N+1)/2)
      !>          On entry, the triangular factor U or L from the Cholesky
      !>          factorization A = U**H*U or A = L*L**H, packed columnwise as
      !>          a linear array.  The j-th column of U or L is stored in the
      !>          array AP as follows:
      !>          if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j;
      !>          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n.
      !>
      !>          On exit, the upper or lower triangle of the (Hermitian)
      !>          inverse of A, overwriting the input factor U or L.
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0:  successful exit
      !>          < 0:  if INFO = -i, the i-th argument had an illegal value
      !>          > 0:  if INFO = i, the (i,i) element of the factor U or L is
      !>                zero, and the inverse could not be computed.
      !>

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