NAME¶

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

SYNOPSIS¶

SUBROUTINE SLAGS2(

UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ )

LOGICAL UPPER REAL A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV, SNQ, SNU, SNV

PURPOSE¶

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

ARGUMENTS¶

UPPER (input) LOGICAL

= .TRUE.: the input matrices A and B are upper triangular.
= .FALSE.: the input matrices A and B are lower triangular.

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.

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.

CSU (output) REAL

SNU (output) REAL The desired orthogonal matrix U.

CSV (output) REAL

SNV (output) REAL The desired orthogonal matrix V.

CSQ (output) REAL

SNQ (output) REAL The desired orthogonal matrix Q.