NAME¶

SROTM - APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX (SX**T) , WHERE **T INDICATES TRANSPOSE

SYNOPSIS¶

SUBROUTINE SROTM(N,SX,INCX,SY,INCY,SPARAM)

INTEGER INCX,INCY,N REAL SPARAM(5),SX(1),SY(1)

PURPOSE¶

APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX
(DX**T)

SX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
LX = (-INCX)*N, AND SIMILARLY FOR SY USING USING LY AND INCY.
WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..

SFLAG=-1.E0 SFLAG=0.E0 SFLAG=1.E0 SFLAG=-2.E0

(SH11 SH12) (1.E0 SH12) (SH11 1.E0) (1.E0 0.E0)
H=( ) ( ) ( ) ( )
(SH21 SH22), (SH21 1.E0), (-1.E0 SH22), (0.E0 1.E0).
SEE SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM.

ARGUMENTS¶

N (input) INTEGER

number of elements in input vector(s)

SX (input/output) REAL array, dimension N

double precision vector with 5 elements

INCX (input) INTEGER

storage spacing between elements of SX

SY (input/output) REAL array, dimension N

double precision vector with N elements

INCY (input) INTEGER

storage spacing between elements of SY

SPARAM (input/output) REAL array, dimension 5 SPARAM(1)=SFLAG SPARAM(2)=SH11 SPARAM(3)=SH21 SPARAM(4)=SH12 SPARAM(5)=SH22