clags2-f(3)

clags2.f –

Synopsis

Functions/Subroutines

subroutine clags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
CLAGS2

Function/Subroutine Documentation

subroutine clags2 (logicalUPPER, realA1, complexA2, realA3, realB1, complexB2, realB3, realCSU, complexSNU, realCSV, complexSNV, realCSQ, complexSNQ)

CLAGS2

Purpose:

 CLAGS2 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 is REAL

 A2 is COMPLEX

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

 B1 is REAL

 B2 is COMPLEX

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

CSU

 CSU is REAL

SNU

 SNU is COMPLEX
 The desired unitary matrix U.

CSV

 CSV is REAL

SNV

 SNV is COMPLEX
 The desired unitary matrix V.

CSQ

 CSQ is REAL

SNQ

 SNQ is COMPLEX
 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 clags2.f.

Author

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