LAPACK  3.4.0
LAPACK: Linear Algebra PACKage
Functions/Subroutines
slags2.f File Reference

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Functions/Subroutines

subroutine SLAGS2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
 SLAGS2

Function/Subroutine Documentation

subroutine SLAGS2 ( LOGICAL  UPPER,
REAL  A1,
REAL  A2,
REAL  A3,
REAL  B1,
REAL  B2,
REAL  B3,
REAL  CSU,
REAL  SNU,
REAL  CSV,
REAL  SNV,
REAL  CSQ,
REAL  SNQ 
)

SLAGS2

Download SLAGS2 + dependencies [TGZ] [ZIP] [TXT]
Purpose: 

 SLAGS2 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 REAL
[in]A2
          A2 is REAL
[in]A3
          A3 is REAL
          On entry, A1, A2 and A3 are elements of the input 2-by-2
          upper (lower) triangular matrix A.
[in]B1
          B1 is REAL
[in]B2
          B2 is REAL
[in]B3
          B3 is REAL
          On entry, B1, B2 and B3 are elements of the input 2-by-2
          upper (lower) triangular matrix B.
[out]CSU
          CSU is REAL
[out]SNU
          SNU is REAL
          The desired orthogonal matrix U.
[out]CSV
          CSV is REAL
[out]SNV
          SNV is REAL
          The desired orthogonal matrix V.
[out]CSQ
          CSQ is REAL
[out]SNQ
          SNQ is REAL
          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 slags2.f.

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