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## ctrtri()

subroutine ctrtri | ( | character | uplo,
|  | character | diag,
|  | integer | n,
|  | complex, dimension( lda, * ) | a,
|  | integer | lda,
|  | integer | info )

CTRTRI

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

Purpose:

      !>
      !> CTRTRI computes the inverse of a complex upper or lower triangular
      !> matrix A.
      !>
      !> This is the Level 3 BLAS version of the algorithm.
      !>

Parameters

  [in]

  UPLO

      !>          UPLO is CHARACTER*1
      !>          = 'U':  A is upper triangular;
      !>          = 'L':  A is lower triangular.
      !>

  [in]

  DIAG

      !>          DIAG is CHARACTER*1
      !>          = 'N':  A is non-unit triangular;
      !>          = 'U':  A is unit triangular.
      !>

  [in]

  N

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

  [in,out]

  A

      !>          A is COMPLEX array, dimension (LDA,N)
      !>          On entry, the triangular matrix A.  If UPLO = 'U', the
      !>          leading N-by-N upper triangular part of the array A contains
      !>          the upper triangular matrix, and the strictly lower
      !>          triangular part of A is not referenced.  If UPLO = 'L', the
      !>          leading N-by-N lower triangular part of the array A contains
      !>          the lower triangular matrix, and the strictly upper
      !>          triangular part of A is not referenced.  If DIAG = 'U', the
      !>          diagonal elements of A are also not referenced and are
      !>          assumed to be 1.
      !>          On exit, the (triangular) inverse of the original matrix, in
      !>          the same storage format.
      !>

  [in]

  LDA

      !>          LDA is INTEGER
      !>          The leading dimension of the array A.  LDA >= max(1,N).
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0: successful exit
      !>          < 0: if INFO = -i, the i-th argument had an illegal value
      !>          > 0: if INFO = i, A(i,i) is exactly zero.  The triangular
      !>               matrix is singular and its inverse can not be computed.
      !>

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