1DLAGS2(1)           LAPACK auxiliary routine (version 3.1)           DLAGS2(1)
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NAME

6       DLAGS2  - 2-by-2 orthogonal matrices U, V and Q, such that if ( UPPER )
7       then   U'*A*Q = U'*( A1 A2 )*Q = ( x 0 )  ( 0 A3 ) ( x x ) and   V'*B*Q
8       = V'*( B1 B2 )*Q = ( x 0 )  ( 0 B3 ) ( x x )  or if ( .NOT.UPPER ) then
9       U'*A*Q = U'*( A1 0 )*Q = ( x x )  ( A2 A3 ) ( 0 x ) and  V'*B*Q =  V'*(
10       B1  0  )*Q  = ( x x )  ( B2 B3 ) ( 0 x )  The rows of the transformed A
11       and B are parallel, where   U = ( CSU SNU ), V = ( CSV SNV ), Q = ( CSQ
12       SNQ )  ( -SNU CSU ) ( -SNV CSV ) ( -SNQ CSQ )  Z' denotes the transpose
13       of Z
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SYNOPSIS

16       SUBROUTINE DLAGS2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU,  CSV,  SNV,
17                          CSQ, SNQ )
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19           LOGICAL        UPPER
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21           DOUBLE         PRECISION  A1,  A2,  A3,  B1, B2, B3, CSQ, CSU, CSV,
22                          SNQ, SNU, SNV
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PURPOSE

25       DLAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such that  if  (
26       UPPER ) then
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ARGUMENTS

31       UPPER   (input) LOGICAL
32               = .TRUE.: the input matrices A and B are upper triangular.
33               = .FALSE.: the input matrices A and B are lower triangular.
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35       A1      (input) DOUBLE PRECISION
36               A2       (input) DOUBLE PRECISION A3      (input) DOUBLE PRECI‐
37               SION On entry, A1, A2 and A3 are elements of the  input  2-by-2
38               upper (lower) triangular matrix A.
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40       B1      (input) DOUBLE PRECISION
41               B2       (input) DOUBLE PRECISION B3      (input) DOUBLE PRECI‐
42               SION On entry, B1, B2 and B3 are elements of the  input  2-by-2
43               upper (lower) triangular matrix B.
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45       CSU     (output) DOUBLE PRECISION
46               SNU     (output) DOUBLE PRECISION The desired orthogonal matrix
47               U.
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49       CSV     (output) DOUBLE PRECISION
50               SNV     (output) DOUBLE PRECISION The desired orthogonal matrix
51               V.
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53       CSQ     (output) DOUBLE PRECISION
54               SNQ     (output) DOUBLE PRECISION The desired orthogonal matrix
55               Q.
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59 LAPACK auxiliary routine (versionNo3v.e1m)ber 2006                       DLAGS2(1)
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