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

Chapter 2 Basic Vector Operations 123
Apply modified Givens rotation SROTM/DROTM
Name SROTM/DROTM
Apply modified Givens rotation
Purpose Given a modified Givens rotation matrix H = {h
ij
} as constructed by SROTMG
or DROTMG, and real vectors x and y of length n, these subprograms apply the
modified rotation
Refer to the description of the companion subprograms SROTMG and
DROTMG for more details about the modified Givens rotation.
The vectors can be stored in one-dimensional arrays or in either rows or
columns of two-dimensional arrays, and the indexing through the arrays can be
either forward or backward.
Usage VECLIB:
INTEGER*4 n, incx, incy
REAL*4 x(lenx), y(leny), param(5)
CALL SROTM(n, x, incx, y, incy, param)
INTEGER*4 n, incx, incy
REAL*8 x(lenx), y(leny), param(5)
CALL DROTM(n, x, incx, y, incy, param)
VECLIB8:
INTEGER*8 n, incx, incy
REAL*4 x(lenx), y(leny), param(5)
CALL SROTM(n, x, incx, y, incy, param)
INTEGER*8 n, incx, incy
REAL*8 x(lenx), y(leny), param(5)
CALL DROTM(n, x, incx, y, incy, param)
Input n Number of elements of vectors x and y to be used. If
n ≤ 0, the subprograms do not reference x or y.
x Array of length lenx = (n−1)×|incx|+1 containing the
n-vector x.
incx Increment for the array x, incx ≠ 0:
incx > 0 x is stored forward in array x; that is,
x
i
is stored in x((i−1)×incx+1).
x
i
y
i
h
11
h
12
h
21
h
22
←
x
i
y
i
⋅ for i 1 … n.,,=