SROTM(3)

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

NAME
srotm - Apply a modified Givens transformation.

LIBRARY
SLATEC (BLAS)

CATEGORY
D1A8

TYPE
SINGLE PRECISION (SROTM-S, DROTM-D)

KEYWORDS
BLAS, LINEAR ALGEBRA, MODIFIED GIVENS ROTATION, VECTOR

AUTHOR
Lawson, C. L., (JPL) Hanson, R. J., (SNLA) Kincaid, D. R., (U. of Texas) Krogh, F. T., (JPL)

DESCRIPTION
B L A S Subprogram Description of Parameters --Input-- N number of elements in input vector(s) SX single precision vector with N elements INCX storage spacing between elements of SX SY single precision vector with N elements INCY storage spacing between elements of SY SPARAM 5-element vector. SPARAM(1) is SFLAG described below. Locations 2-5 of SPARAM contain elements of the transformation matrix H described below. --Output-- SX rotated vector (unchanged if N .LE. 0) SY rotated vector (unchanged if N .LE. 0) Apply the modified Givens transformation, H, to the 2 by N matrix (SX**T) (SY**T) , where **T indicates transpose. The elements of SX are in SX(LX+I*INCX), I = 0 to N-1, where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and similarly for SY 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.

REFERENCES
C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T. Krogh, Basic linear algebra subprograms for Fortran usage, Algorithm No. 539, Transactions on Mathematical Software 5, 3 (September 1979), pp. 308-323.

ROUTINES CALLED
(NONE)

REVISION HISTORY (YYMMDD)
791001 DATE WRITTEN
861211 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
920310 Corrected definition of LX in DESCRIPTION. (WRB)
920501 Reformatted the REFERENCES section. (WRB)