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C Library Functions  - drotmg (3)

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NAME

drotmg(3f) - [BLAS:DOUBLE_BLAS_LEVEL1]

CONTENTS

Synopsis
Definition
Options
Authors
See Also

SYNOPSIS

subroutine drotmg(dd1,dd2,dx1,dy1,dparam)

      .. Scalar Arguments ..
      double precision,intent(inout) :: dd1,dd2,dx1
      double precision,intent(in)    :: dy1
      ..
      .. Array Arguments ..
      double precision,intent(out)   :: dparam(5)
      ..

DEFINITION

    CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS

THE SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)*> DY2)**T. WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..

       DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0

         (DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0)
       H=(          )    (          )    (          )    (          )
         (DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0).

LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22 RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)

    THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE

INEXACT. THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE OF DD1 AND DD2. ALL ACTUAL SCALING OF DATA IS DONE USING GAM.

OPTIONS

DD1

          DD1 is DOUBLE PRECISION

DD2

          DD2 is DOUBLE PRECISION

DX1

          DX1 is DOUBLE PRECISION

DY1

          DY1 is DOUBLE PRECISION

    DPARAM

DPARAM is DOUBLE PRECISION array, dimension (5) DPARAM(1)=DFLAG DPARAM(2)=DH11 DPARAM(3)=DH21 DPARAM(4)=DH12 DPARAM(5)=DH22

AUTHORS

o	Univ. of Tennessee
o	Univ. of California Berkeley
o	Univ. of Colorado Denver
o	NAG Ltd.

 date:November 2017

SEE ALSO

Online html documentation available at http://www.netlib.org/lapack/explore-html/

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Nemo Release 3.1

drotmg (3)

February 23, 2025

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