DROTMG(1) BLAS routine DROTMG(1)NAME
DROTMG - CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH
ZEROS THE SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)*
SYNOPSIS
SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)
DOUBLE PRECISION DD1,DD2,DX1,DY1
DOUBLE PRECISION DPARAM(5)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.
ARGUMENTS
DD1 (input/output) DOUBLE PRECISION
DD2 (input/output) DOUBLE PRECISION
DX1 (input/output) DOUBLE PRECISION
DY1 (input) DOUBLE PRECISION
DPARAM (input/output) DOUBLE PRECISION array, dimension 5
DPARAM(1)=DFLAG DPARAM(2)=DH11 DPARAM(3)=DH21 DPARAM(4)=DH12
DPARAM(5)=DH22
BLAS routine November 2008 DROTMG(1)
