Previous: sgbtrs Up: ../lapack-s.html Next: sgebal

sgebak

 NAME
      SGEBAK - form the right or left eigenvectors of a real gen-
      eral matrix by backward transformation on the computed
      eigenvectors of the balanced matrix output by SGEBAL

 SYNOPSIS
      SUBROUTINE SGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV,
                         INFO )

          CHARACTER      JOB, SIDE

          INTEGER        IHI, ILO, INFO, LDV, M, N

          REAL           V( LDV, * ), SCALE( * )

 PURPOSE
      SGEBAK forms the right or left eigenvectors of a real gen-
      eral matrix by backward transformation on the computed
      eigenvectors of the balanced matrix output by SGEBAL.

 ARGUMENTS
      JOB     (input) CHARACTER*1
              Specifies the type of backward transformation
              required: = 'N', do nothing, return immediately; =
              'P', do backward transformation for permutation
              only; = 'S', do backward transformation for scaling
              only; = 'B', do backward transformations for both
              permutation and scaling.  JOB must be the same as
              the argument JOB supplied to SGEBAL.

      SIDE    (input) CHARACTER*1
              = 'R':  V contains right eigenvectors;
              = 'L':  V contains left eigenvectors.

      N       (input) INTEGER
              The number of rows of the matrix V.  N >= 0.

      ILO     (input) INTEGER
              IHI     (input) INTEGER The integers ILO and IHI
              determined by SGEBAL.

      SCALE   (input) REAL array, dimension (N)
              Details of the permutation and scaling factors, as
              returned by SGEBAL.

      M       (input) INTEGER
              The number of columns of the matrix V.

      V       (input/output) REAL array, dimension (LDV,M)
              On entry, the matrix of right or left eigenvectors
              to be transformed, as returned by SHSEIN or STREVC.

              On exit, V is overwritten by the transformed eigen-
              vectors.

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

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