ZLAGS2 computes 2-by-2 unitary matrices U, V and Q, such


 that if ( UPPER ) then


           U**H *A*Q = U**H *( A1 A2 )*Q = ( x  0  )


                             ( 0  A3 )     ( x  x  )


 and


           V**H*B*Q = V**H *( B1 B2 )*Q = ( x  0  )


                            ( 0  B3 )     ( x  x  )


 or if ( .NOT.UPPER ) then


           U**H *A*Q = U**H *( A1 0  )*Q = ( x  x  )


                             ( A2 A3 )     ( 0  x  )


 and


           V**H *B*Q = V**H *( B1 0  )*Q = ( x  x  )


                             ( B2 B3 )     ( 0  x  )


 where


   U = (   CSU    SNU ), V = (  CSV    SNV ),


       ( -SNU**H  CSU )      ( -SNV**H CSV )


   Q = (   CSQ    SNQ )


       ( -SNQ**H  CSQ )


 The rows of the transformed A and B are parallel. Moreover, if the


 input 2-by-2 matrix A is not zero, then the transformed (1,1) entry


 of A is not zero. If the input matrices A and B are both not zero,


 then the transformed (2,2) element of B is not zero, except when the


 first rows of input A and B are parallel and the second rows are


 zero.

UPPER

          UPPER is LOGICAL


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


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

A1

          A1 is DOUBLE PRECISION

A2

          A2 is COMPLEX*16

A3

          A3 is DOUBLE PRECISION


          On entry, A1, A2 and A3 are elements of the input 2-by-2


          upper (lower) triangular matrix A.

B1

          B1 is DOUBLE PRECISION

B2

          B2 is COMPLEX*16

B3

          B3 is DOUBLE PRECISION


          On entry, B1, B2 and B3 are elements of the input 2-by-2


          upper (lower) triangular matrix B.

CSU

          CSU is DOUBLE PRECISION

SNU

          SNU is COMPLEX*16


          The desired unitary matrix U.

CSV

          CSV is DOUBLE PRECISION

SNV

          SNV is COMPLEX*16


          The desired unitary matrix V.

CSQ

          CSQ is DOUBLE PRECISION

SNQ

          SNQ is COMPLEX*16


          The desired unitary matrix Q.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

December 2016