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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 computes 2-by-2 orthogonal matrices U, V, and Q, and applies them to matrices A and B such that the rows of the transformed A and B are parallel.

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 computes 2-by-2 orthogonal matrices U, V, and Q, and applies them to matrices A and B such that the rows of the transformed A and B are parallel.

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:

September 2012

Definition at line 152 of file dlags2.f.

Author

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Tue Sep 25 2012 Version 3.4.2