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dlags2.f(3) LAPACK dlags2.f(3)

NAME

dlags2.f -

SYNOPSIS

Functions/Subroutines


subroutine dlags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
 
DLAGS2

Function/Subroutine Documentation

subroutine dlags2 (logicalUPPER, double precisionA1, double precisionA2, double precisionA3, double precisionB1, double precisionB2, double precisionB3, double precisionCSU, double precisionSNU, double precisionCSV, double precisionSNV, double precisionCSQ, double precisionSNQ)

DLAGS2
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:
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 DOUBLE PRECISION
 
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 DOUBLE PRECISION
 
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 DOUBLE PRECISION
          The desired orthogonal matrix U.
 
CSV 
          CSV is DOUBLE PRECISION
 
SNV 
          SNV is DOUBLE PRECISION
          The desired orthogonal matrix V.
 
CSQ 
          CSQ is DOUBLE PRECISION
 
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.

Author

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