• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

dgebak - form the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL

SYNOPSIS

  SUBROUTINE DGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, INFO)
  CHARACTER * 1 JOB, SIDE
  INTEGER N, ILO, IHI, M, LDV, INFO
  DOUBLE PRECISION SCALE(*), V(LDV,*)

  SUBROUTINE DGEBAK_64( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, 
 *      INFO)
  CHARACTER * 1 JOB, SIDE
  INTEGER*8 N, ILO, IHI, M, LDV, INFO
  DOUBLE PRECISION SCALE(*), V(LDV,*)

F95 INTERFACE

  SUBROUTINE GEBAK( JOB, SIDE, [N], ILO, IHI, SCALE, [M], V, [LDV], 
 *       [INFO])
  CHARACTER(LEN=1) :: JOB, SIDE
  INTEGER :: N, ILO, IHI, M, LDV, INFO
  REAL(8), DIMENSION(:) :: SCALE
  REAL(8), DIMENSION(:,:) :: V

  SUBROUTINE GEBAK_64( JOB, SIDE, [N], ILO, IHI, SCALE, [M], V, [LDV], 
 *       [INFO])
  CHARACTER(LEN=1) :: JOB, SIDE
  INTEGER(8) :: N, ILO, IHI, M, LDV, INFO
  REAL(8), DIMENSION(:) :: SCALE
  REAL(8), DIMENSION(:,:) :: V

C INTERFACE

#include <sunperf.h>

void dgebak(char job, char side, int n, int ilo, int ihi, double *scale, int m, double *v, int ldv, int *info);

void dgebak_64(char job, char side, long n, long ilo, long ihi, double *scale, long m, double *v, long ldv, long *info);

PURPOSE

dgebak forms the right or left eigenvectors of a real general matrix by backward transformation on the computed eigenvectors of the balanced matrix output by SGEBAL.

ARGUMENTS

• JOB (input)
  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)
  

   = 'R':  V contains right eigenvectors;

   = 'L':  V contains left eigenvectors.

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

• ILO (input)
  The integers ILO and IHI determined by SGEBAL. 1 < = ILO < = IHI < = N, if N > 0; ILO =1 and IHI =0, if N =0.

• IHI (input)
  See the description for ILO.

• SCALE (input)
  Details of the permutation and scaling factors, as returned by SGEBAL.

• M (input)
  The number of columns of the matrix V. M > = 0.

• V (input/output)
  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 eigenvectors.

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

• INFO (output)
  

   = 0:  successful exit

   < 0:  if INFO  = -i, the i-th argument had an illegal value.