SSYTRI_ROOK computes the inverse of a real symmetric


 matrix A using the factorization A = U*D*U**T or A = L*D*L**T


 computed by SSYTRF_ROOK.

UPLO

          UPLO is 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

          N is INTEGER


          The order of the matrix A.  N >= 0.

A

          A is REAL 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 SSYTRF_ROOK.


          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

          LDA is INTEGER


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

IPIV

          IPIV is INTEGER array, dimension (N)


          Details of the interchanges and the block structure of D


          as determined by SSYTRF_ROOK.

WORK

          WORK is REAL array, dimension (N)

INFO

          INFO is 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.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

   April 2012, Igor Kozachenko,


                  Computer Science Division,


                  University of California, Berkeley


  September 2007, Sven Hammarling, Nicholas J. Higham, Craig Lucas,


                  School of Mathematics,


                  University of Manchester