HP MLIB User's Guide Vol. 1 7th Ed.

128 HP MLIB User’s Guide
SROTMG/DROTMG Construct modified Givens rotation
Usage VECLIB, VECLIB8:
REAL*4 d1, d2, x1, y1, param(5)
CALL SROTMG(d1, d2, x1, y1, param)
REAL*8 d1, d2, x1, y1, param(5)
CALL DROTMG(d1, d2, x1, y1, param)
Input d1 The scale factor for the “x” row.
d2 The scale factor for the “y” row.
x1 The first element of the “x” row.
y1 The first element of the “y” row. This is the element
that is annihilated by the rotation.
Output d1 The updated scale factor for the “x” row.
d2 The updated scale factor for the “y” row.
x1 The rotated first element of the “x” row.
param Array containing the matrix elements of the modified
Givens rotation matrix H and a flag indicating which
form the rotation matrix H takes and, therefore, which
elements of param are significant. param is usually an
argument to the companion subprogram SROTM or
DROTM.
param(1) specifies the form of the rotation matrix H, as
follows:
param(1) 2–= H
10
01
=
param 1() 1–= H
param 2() param 4()
param 3() param 5()
=
param 1() 0= H
1 param 4()
param 3() 1
=