drotm (l) - Linux Manuals

drotm: APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX (DX**T) , WHERE **T INDICATES TRANSPOSE

NAME

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

SYNOPSIS

SUBROUTINE DROTM(N,DX,INCX,DY,INCY,DPARAM)

    

INTEGER INCX,INCY,N

    

DOUBLE PRECISION DPARAM(5),DX(1),DY(1)

PURPOSE

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

DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE
LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY.
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).
SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM.

ARGUMENTS

N (input) INTEGER

number of elements in input vector(s)

DX (input/output) DOUBLE PRECISION array, dimension N

double precision vector with 5 elements

INCX (input) INTEGER

storage spacing between elements of DX

DY (input/output) DOUBLE PRECISION array, dimension N

double precision vector with N elements

INCY (input) INTEGER

storage spacing between elements of DY

DPARAM (input/output) DOUBLE PRECISION array, dimension 5 DPARAM(1)=DFLAG DPARAM(2)=DH11 DPARAM(3)=DH21 DPARAM(4)=DH12 DPARAM(5)=DH22