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NAME CLAGS2 - compute 2-by-2 unitary 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 ) where U = ( CSU SNU ), V = ( CSV SNV ), SYNOPSIS SUBROUTINE CLAGS2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ ) LOGICAL UPPER REAL A1, A3, B1, B3, CSQ, CSU, CSV COMPLEX A2, B2, SNQ, SNU, SNV PURPOSE CLAGS2 computes 2-by-2 unitary matrices U, V and Q, such that if ( UPPER ) then ( -CONJG(SNU) CSU ) ( -CONJG(SNV) CSV ) Q = ( CSQ SNQ ) ( -CONJG(SNQ) CSQ ) Z' denotes the conjugate transpose of Z. 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) entry of B is not zero, except when the first rows of input A and B are parallel and the second rows are zero. ARGUMENTS UPPER (input) LOGICAL = .TRUE.: the input matrices A and B are upper tri- angular. = .FALSE.: the input matrices A and B are lower tri- angular. A1 (input) REAL A2 (input) COMPLEX A3 (input) REAL On entry, A1, A2 and A3 are entries of the input 2-by-2 upper (lower) triangular matrix A. B1 (input) REAL B2 (input) COMPLEX B3 (input) REAL On entry, B1, B2 and B3 are entries of the input 2-by-2 upper (lower) triangular matrix B. CSU (output) REAL SNU (output) COMPLEX The desired unitary matrix U. CSV (output) REAL SNV (output) COMPLEX The desired unitary matrix V. CSQ (output) REAL SNQ (output) COMPLEX The desired unitary matrix Q.