2. EL 7
  3. lapack
  4. clags2.f(3)

Scroll to navigation

clags2.f(3) LAPACK clags2.f(3)

NAME

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



          A1 is REAL

A2



          A2 is COMPLEX

A3



          A3 is REAL


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


          upper (lower) triangular matrix A.

B1



          B1 is REAL

B2



          B2 is COMPLEX

B3



          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

Generated automatically by Doxygen for LAPACK from the source code.

Tue Sep 25 2012 Version 3.4.2