
NAMEzlags2.f SYNOPSISFunctions/Subroutinessubroutine zlags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ) Function/Subroutine Documentationsubroutine zlags2 (logicalUPPER, double precisionA1, complex*16A2, double precisionA3, double precisionB1, complex*16B2, double precisionB3, double precisionCSU, complex*16SNU, double precisionCSV, complex*16SNV, double precisionCSQ, complex*16SNQ)ZLAGS2 Purpose:ZLAGS2 computes 2by2 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 2by2 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
Author:
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 PRECISIONA2 A2 is COMPLEX*16A3 A3 is DOUBLE PRECISION On entry, A1, A2 and A3 are elements of the input 2by2 upper (lower) triangular matrix A.B1 B1 is DOUBLE PRECISIONB2 B2 is COMPLEX*16B3 B3 is DOUBLE PRECISION On entry, B1, B2 and B3 are elements of the input 2by2 upper (lower) triangular matrix B.CSU CSU is DOUBLE PRECISIONSNU SNU is COMPLEX*16 The desired unitary matrix U.CSV CSV is DOUBLE PRECISIONSNV SNV is COMPLEX*16 The desired unitary matrix V.CSQ CSQ is DOUBLE PRECISIONSNQ SNQ is COMPLEX*16 The desired unitary matrix Q. Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Definition at line 158 of file zlags2.f.
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