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LAPACK version 3.0
dsytri(3)

PURPOSE
  DSYTRI - compute the inverse of a real symmetric indefinite matrix A using
  the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF

SYNTAX
  SUBROUTINE DSYTRI( UPLO, N, A, LDA, IPIV, WORK, INFO )

      CHARACTER	     UPLO

      INTEGER	     INFO, LDA, N

      INTEGER	     IPIV( * )

      DOUBLE	     PRECISION A( LDA, * ), WORK( * )

DESCRIPTION
  DSYTRI computes the inverse of a real symmetric indefinite matrix A using
  the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF.

ARGUMENTS
  UPLO	  (input) CHARACTER*1
	  Specifies whether the details of the factorization are stored as an
	  upper or lower triangular matrix.  = 'U':  Upper triangular, form
	  is A = U*D*U**T;
	  = 'L':  Lower triangular, form is A = L*D*L**T.

  N	  (input) INTEGER
	  The order of the matrix A.  N >= 0.

  A	  (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	  On entry, the block diagonal matrix D and the multipliers used to
	  obtain the factor U or L as computed by DSYTRF.

	  On exit, if INFO = 0, the (symmetric) inverse of the original
	  matrix.  If UPLO = 'U', the upper triangular part of the inverse is
	  formed and the part of A below the diagonal is not referenced; if
	  UPLO = 'L' the lower triangular part of the inverse is formed and
	  the part of A above the diagonal is not referenced.

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

  IPIV	  (input) INTEGER array, dimension (N)
	  Details of the interchanges and the block structure of D as
	  determined by DSYTRF.

  WORK	  (workspace) DOUBLE PRECISION array, dimension (N)

  INFO	  (output) INTEGER
	  = 0: successful exit
	  < 0: if INFO = -i, the i-th argument had an illegal value
	  > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its
	  inverse could not be computed.