NAME

BLAS/SRC/drotmg.f

SYNOPSIS

Functions/Subroutines

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

Function/Subroutine Documentation

subroutine drotmg (double precision dd1, double precision dd2, double precision dx1, double precision dy1, double precision, dimension(5) dparam)

DROTMG

Purpose:



    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.

Parameters

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

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 89 of file drotmg.f.

Author

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