1DROTMG(1)                        BLAS routine                        DROTMG(1)
2
3
4

NAME

6       DROTMG  -  THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS  THE
7       SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)*
8

SYNOPSIS

10       SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)
11
12           DOUBLE                                PRECISION DD1,DD2,DX1,DY1
13
14           DOUBLE                                PRECISION DPARAM(5)
15

PURPOSE

17          CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
18          THE SECOND COMPONENT OF THE 2-VECTOR  (DSQRT(DD1)*DX1,DSQRT(DD2)*
19          DY2)**T.
20          WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
21
22          DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0
23
24            (DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0)
25          H=(          )    (          )    (          )    (          )
26            (DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0).
27          LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22
28          RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE
29          VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)
30
31          THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE
32          INEXACT.  THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE
33          OF DD1 AND DD2.  ALL ACTUAL SCALING OF DATA IS DONE USING GAM.
34
35
36

ARGUMENTS

38       DD1    (input/output) DOUBLE PRECISION
39
40       DD2    (input/output) DOUBLE PRECISION
41
42       DX1    (input/output) DOUBLE PRECISION
43
44       DY1    (input) DOUBLE PRECISION
45
46              DPARAM  (input/output)   DOUBLE  PRECISION  array,  dimension  5
47              DPARAM(1)=DFLAG   DPARAM(2)=DH11  DPARAM(3)=DH21  DPARAM(4)=DH12
48              DPARAM(5)=DH22
49
50
51
52BLAS routine                     February 2007                       DROTMG(1)