LAPACK  3.4.0
LAPACK: Linear Algebra PACKage
Functions/Subroutines
dlags2.f File Reference

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Functions/Subroutines

subroutine DLAGS2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
 DLAGS2

Function/Subroutine Documentation

subroutine DLAGS2 ( LOGICAL  UPPER,
DOUBLE PRECISION  A1,
DOUBLE PRECISION  A2,
DOUBLE PRECISION  A3,
DOUBLE PRECISION  B1,
DOUBLE PRECISION  B2,
DOUBLE PRECISION  B3,
DOUBLE PRECISION  CSU,
DOUBLE PRECISION  SNU,
DOUBLE PRECISION  CSV,
DOUBLE PRECISION  SNV,
DOUBLE PRECISION  CSQ,
DOUBLE PRECISION  SNQ 
)

DLAGS2

Download DLAGS2 + dependencies [TGZ] [ZIP] [TXT]
Purpose: 

 DLAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such
 that if ( UPPER ) then

           U**T *A*Q = U**T *( A1 A2 )*Q = ( x  0  )
                             ( 0  A3 )     ( x  x  )
 and
           V**T*B*Q = V**T *( B1 B2 )*Q = ( x  0  )
                            ( 0  B3 )     ( x  x  )

 or if ( .NOT.UPPER ) then

           U**T *A*Q = U**T *( A1 0  )*Q = ( x  x  )
                             ( A2 A3 )     ( 0  x  )
 and
           V**T*B*Q = V**T*( B1 0  )*Q = ( x  x  )
                           ( B2 B3 )     ( 0  x  )

 The rows of the transformed A and B are parallel, where

   U = (  CSU  SNU ), V = (  CSV SNV ), Q = (  CSQ   SNQ )
       ( -SNU  CSU )      ( -SNV CSV )      ( -SNQ   CSQ )

 Z**T denotes the transpose of Z.
Parameters:
[in]UPPER
          UPPER is LOGICAL
          = .TRUE.: the input matrices A and B are upper triangular.
          = .FALSE.: the input matrices A and B are lower triangular.
[in]A1
          A1 is DOUBLE PRECISION
[in]A2
          A2 is DOUBLE PRECISION
[in]A3
          A3 is DOUBLE PRECISION
          On entry, A1, A2 and A3 are elements of the input 2-by-2
          upper (lower) triangular matrix A.
[in]B1
          B1 is DOUBLE PRECISION
[in]B2
          B2 is DOUBLE PRECISION
[in]B3
          B3 is DOUBLE PRECISION
          On entry, B1, B2 and B3 are elements of the input 2-by-2
          upper (lower) triangular matrix B.
[out]CSU
          CSU is DOUBLE PRECISION
[out]SNU
          SNU is DOUBLE PRECISION
          The desired orthogonal matrix U.
[out]CSV
          CSV is DOUBLE PRECISION
[out]SNV
          SNV is DOUBLE PRECISION
          The desired orthogonal matrix V.
[out]CSQ
          CSQ is DOUBLE PRECISION
[out]SNQ
          SNQ is DOUBLE PRECISION
          The desired orthogonal matrix Q.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011

Definition at line 152 of file dlags2.f.

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