dlags2.f man page

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

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dlags2(3) is an alias of dlags2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK