1SLAGS2(1)           LAPACK auxiliary routine (version 3.2)           SLAGS2(1)
2
3
4

NAME

6       SLAGS2 - computes 2-by-2 orthogonal matrices U, V and Q, such that if (
7       UPPER ) then   U'*A*Q = U'*( A1 A2 )*Q = ( x 0 )  ( 0 A3 ) ( x x )  and
8       V'*B*Q = V'*( B1 B2 )*Q = ( x 0 )  ( 0 B3 ) ( x x )  or if ( .NOT.UPPER
9       ) then   U'*A*Q = U'*( A1 0 )*Q = ( x x )  ( A2  A3  )  (  0  x  )  and
10       V'*B*Q  =  V'*(  B1 0 )*Q = ( x x )  ( B2 B3 ) ( 0 x )  The rows of the
11       transformed A and B are parallel, where   U = ( CSU SNU ), V  =  (  CSV
12       SNV  ),  Q  =  (  CSQ SNQ )  ( -SNU CSU ) ( -SNV CSV ) ( -SNQ CSQ )  Z'
13       denotes the transpose of Z
14

SYNOPSIS

16       SUBROUTINE SLAGS2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU,  CSV,  SNV,
17                          CSQ, SNQ )
18
19           LOGICAL        UPPER
20
21           REAL           A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV, SNQ, SNU, SNV
22

PURPOSE

24       SLAGS2  computes  2-by-2 orthogonal matrices U, V and Q, such that if (
25       UPPER ) then
26

ARGUMENTS

28       UPPER   (input) LOGICAL
29               = .TRUE.: the input matrices A and B are upper triangular.
30               = .FALSE.: the input matrices A and B are lower triangular.
31
32       A1      (input) REAL
33               A2      (input) REAL A3      (input) REAL On entry, A1, A2  and
34               A3  are  elements  of the input 2-by-2 upper (lower) triangular
35               matrix A.
36
37       B1      (input) REAL
38               B2      (input) REAL B3      (input) REAL On entry, B1, B2  and
39               B3  are  elements  of the input 2-by-2 upper (lower) triangular
40               matrix B.
41
42       CSU     (output) REAL
43               SNU     (output) REAL The desired orthogonal matrix U.
44
45       CSV     (output) REAL
46               SNV     (output) REAL The desired orthogonal matrix V.
47
48       CSQ     (output) REAL
49               SNQ     (output) REAL The desired orthogonal matrix Q.
50
51
52
53 LAPACK auxiliary routine (versionNo3v.e2m)ber 2008                       SLAGS2(1)
Impressum