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.TH SLAGS2 l "15 June 2000" "LAPACK version 3.0" ")"
.SH NAME
SLAGS2 - compute 2-by-2 orthogonal matrices U, V and Q, such that if ( UPPER ) then U'*A*Q = U'*( A1 A2 )*Q = ( x 0 ) ( 0 A3 ) ( x x ) and V'*B*Q = V'*( B1 B2 )*Q = ( x 0 ) ( 0 B3 ) ( x x ) or if ( .NOT.UPPER ) then U'*A*Q = U'*( A1 0 )*Q = ( x x ) ( A2 A3 ) ( 0 x ) and V'*B*Q = V'*( B1 0 )*Q = ( x x ) ( B2 B3 ) ( 0 x ) The rows of the transformed A and B are parallel, where U = ( CSU SNU ), V = ( CSV SNV ), Q = ( CSQ SNQ ) ( -SNU CSU ) ( -SNV CSV ) ( -SNQ CSQ ) Z' denotes the transpose of Z
.SH SYNOPSIS
.TP 19
SUBROUTINE SLAGS2(
UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV,
SNV, CSQ, SNQ )
.TP 19
.ti +4
LOGICAL
UPPER
.TP 19
.ti +4
REAL
A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV, SNQ,
SNU, SNV
.SH PURPOSE
SLAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such that if ( UPPER ) then U'*A*Q = U'*( A1 A2 )*Q = ( x 0 ) ( 0 A3 ) ( x x ) and V'*B*Q = V'*( B1 B2 )*Q = ( x 0 ) ( 0 B3 ) ( x x ) or if ( .NOT.UPPER ) then U'*A*Q = U'*( A1 0 )*Q = ( x x ) ( A2 A3 ) ( 0 x ) and V'*B*Q = V'*( B1 0 )*Q = ( x x ) ( B2 B3 ) ( 0 x ) The rows of the transformed A and B are parallel, where U = ( CSU SNU ), V = ( CSV SNV ), Q = ( CSQ SNQ ) ( -SNU CSU ) ( -SNV CSV ) ( -SNQ CSQ ) Z' denotes the transpose of Z.
.SH ARGUMENTS
.TP 8
UPPER (input) LOGICAL
= .TRUE.: the input matrices A and B are upper triangular.
.br
= .FALSE.: the input matrices A and B are lower triangular.
.TP 8
A1 (input) REAL
A2 (input) REAL
A3 (input) REAL
On entry, A1, A2 and A3 are elements of the input 2-by-2
upper (lower) triangular matrix A.
.TP 8
B1 (input) REAL
B2 (input) REAL
B3 (input) REAL
On entry, B1, B2 and B3 are elements of the input 2-by-2
upper (lower) triangular matrix B.
.TP 8
CSU (output) REAL
SNU (output) REAL
The desired orthogonal matrix U.
.TP 8
CSV (output) REAL
SNV (output) REAL
The desired orthogonal matrix V.
.TP 8
CSQ (output) REAL
SNQ (output) REAL
The desired orthogonal matrix Q.
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