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zlags2.f(3) LAPACK zlags2.f(3)

NAME

zlags2.f -

SYNOPSIS

Functions/Subroutines


subroutine zlags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
 
ZLAGS2

Function/Subroutine Documentation

subroutine 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 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.
Parameters:
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.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Definition at line 158 of file zlags2.f.

Author

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