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RedHat 9 (Linux i386) - man page for dlags2 (redhat section l)

DLAGS2(l)					)					DLAGS2(l)

NAME
       DLAGS2  -  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

SYNOPSIS
       SUBROUTINE DLAGS2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ )

	   LOGICAL	  UPPER

	   DOUBLE	  PRECISION A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV, SNQ, SNU, SNV

PURPOSE
       DLAGS2 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.

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) DOUBLE PRECISION
	       A2      (input) DOUBLE PRECISION A3	(input) DOUBLE PRECISION On entry, A1, A2
	       and A3 are elements of the input 2-by-2 upper (lower) triangular matrix A.

       B1      (input) DOUBLE PRECISION
	       B2      (input) DOUBLE PRECISION B3	(input) DOUBLE PRECISION On entry, B1, B2
	       and B3 are elements of the input 2-by-2 upper (lower) triangular matrix B.

       CSU     (output) DOUBLE PRECISION
	       SNU     (output) DOUBLE PRECISION The desired orthogonal matrix U.

       CSV     (output) DOUBLE PRECISION
	       SNV     (output) DOUBLE PRECISION The desired orthogonal matrix V.

       CSQ     (output) DOUBLE PRECISION
	       SNQ     (output) DOUBLE PRECISION The desired orthogonal matrix Q.

LAPACK version 3.0			   15 June 2000 				DLAGS2(l)


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