Previous: ssbtrd Up: ../lapack-s.html Next: sspev

sspcon

 NAME
      SSPCON - estimate the reciprocal of the condition number (in
      the 1-norm) of a real symmetric packed matrix A using the
      factorization A = U*D*U**T or A = L*D*L**T computed by
      SSPTRF

 SYNOPSIS
      SUBROUTINE SSPCON( UPLO, N, AP, IPIV, ANORM, RCOND, WORK,
                         IWORK, INFO )

          CHARACTER      UPLO

          INTEGER        INFO, N

          REAL           ANORM, RCOND

          INTEGER        IPIV( * ), IWORK( * )

          REAL           AP( * ), WORK( * )

 PURPOSE
      SSPCON estimates the reciprocal of the condition number (in
      the 1-norm) of a real symmetric packed matrix A using the
      factorization A = U*D*U**T or A = L*D*L**T computed by
      SSPTRF.

      An estimate is obtained for norm(inv(A)), and the reciprocal
      of the condition number is computed as RCOND = 1 / (ANORM *
      norm(inv(A))).

 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.

      AP      (input) REAL array, dimension (N*(N+1)/2)
              The block diagonal matrix D and the multipliers used
              to obtain the factor U or L as computed by SSPTRF,
              stored as a packed triangular matrix.

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

      ANORM   (input) REAL
              The 1-norm of the original matrix A.

      RCOND   (output) REAL
              The reciprocal of the condition number of the matrix
              A, computed as RCOND = 1/(ANORM * AINVNM), where
              AINVNM is an estimate of the 1-norm of inv(A) com-
              puted in this routine.

      WORK    (workspace) REAL array, dimension (2*N)

      IWORK    (workspace) INTEGER array, dimension (N)

      INFO    (output) INTEGER
              = 0:  successful exit
              < 0:  if INFO = -i, the i-th argument had an illegal
              value