1DGEBAK(1)                LAPACK routine (version 3.2)                DGEBAK(1)
2
3
4

NAME

6       DGEBAK  - forms the right or left eigenvectors of a real general matrix
7       by backward transformation on the computed eigenvectors of the balanced
8       matrix output by DGEBAL
9

SYNOPSIS

11       SUBROUTINE DGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV, INFO )
12
13           CHARACTER      JOB, SIDE
14
15           INTEGER        IHI, ILO, INFO, LDV, M, N
16
17           DOUBLE         PRECISION SCALE( * ), V( LDV, * )
18

PURPOSE

20       DGEBAK forms the right or left eigenvectors of a real general matrix by
21       backward transformation on the computed eigenvectors  of  the  balanced
22       matrix output by DGEBAL.
23

ARGUMENTS

25       JOB     (input) CHARACTER*1
26               Specifies  the type of backward transformation required: = 'N',
27               do nothing, return immediately; = 'P', do backward  transforma‐
28               tion  for  permutation  only; = 'S', do backward transformation
29               for scaling only; = 'B', do backward transformations  for  both
30               permutation  and scaling.  JOB must be the same as the argument
31               JOB supplied to DGEBAL.
32
33       SIDE    (input) CHARACTER*1
34               = 'R':  V contains right eigenvectors;
35               = 'L':  V contains left eigenvectors.
36
37       N       (input) INTEGER
38               The number of rows of the matrix V.  N >= 0.
39
40       ILO     (input) INTEGER
41               IHI     (input) INTEGER The integers ILO and IHI determined  by
42               DGEBAL.   1  <=  ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if
43               N=0.
44
45       SCALE   (input) DOUBLE PRECISION array, dimension (N)
46               Details of the permutation and scaling factors, as returned  by
47               DGEBAL.
48
49       M       (input) INTEGER
50               The number of columns of the matrix V.  M >= 0.
51
52       V       (input/output) DOUBLE PRECISION array, dimension (LDV,M)
53               On entry, the matrix of right or left eigenvectors to be trans‐
54               formed, as returned by DHSEIN or DTREVC.  On exit, V  is  over‐
55               written by the transformed eigenvectors.
56
57       LDV     (input) INTEGER
58               The leading dimension of the array V. LDV >= max(1,N).
59
60       INFO    (output) INTEGER
61               = 0:  successful exit
62               < 0:  if INFO = -i, the i-th argument had an illegal value.
63
64
65
66 LAPACK routine (version 3.2)    November 2008                       DGEBAK(1)
Impressum