LAPACK  3.5.0
LAPACK: Linear Algebra PACKage
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drotmg.f File Reference

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Functions/Subroutines

subroutine drotmg (DD1, DD2, DX1, DY1, DPARAM)
 DROTMG More...
 

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
[in,out]DD1
          DD1 is DOUBLE PRECISION
[in,out]DD2
          DD2 is DOUBLE PRECISION
[in,out]DX1
          DX1 is DOUBLE PRECISION
[in]DY1
          DY1 is DOUBLE PRECISION
[in,out]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.
Date
November 2011

Definition at line 91 of file drotmg.f.

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