LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
 subroutine drotm ( integer N, double precision, dimension(*) DX, integer INCX, double precision, dimension(*) DY, integer INCY, double precision, dimension(5) DPARAM )

DROTM

Purpose:
```    APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX

(DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN
(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.```
Parameters
 [in] N ``` N is INTEGER number of elements in input vector(s)``` [in,out] DX ``` DX is DOUBLE PRECISION array, dimension N double precision vector with N elements``` [in] INCX ``` INCX is INTEGER storage spacing between elements of DX``` [in,out] DY ``` DY is DOUBLE PRECISION array, dimension N double precision vector with N elements``` [in] INCY ``` INCY is INTEGER storage spacing between elements of DY``` [in,out] DPARAM ``` DPARAM is DOUBLE PRECISION array, dimension 5 DPARAM(1)=DFLAG DPARAM(2)=DH11 DPARAM(3)=DH21 DPARAM(4)=DH12 DPARAM(5)=DH22```
Date
November 2011

Definition at line 100 of file drotm.f.

100 *
101 * -- Reference BLAS level1 routine (version 3.4.0) --
102 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
103 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
104 * November 2011
105 *
106 * .. Scalar Arguments ..
107  INTEGER incx,incy,n
108 * ..
109 * .. Array Arguments ..
110  DOUBLE PRECISION dparam(5),dx(*),dy(*)
111 * ..
112 *
113 * =====================================================================
114 *
115 * .. Local Scalars ..
116  DOUBLE PRECISION dflag,dh11,dh12,dh21,dh22,two,w,z,zero
117  INTEGER i,kx,ky,nsteps
118 * ..
119 * .. Data statements ..
120  DATA zero,two/0.d0,2.d0/
121 * ..
122 *
123  dflag = dparam(1)
124  IF (n.LE.0 .OR. (dflag+two.EQ.zero)) RETURN
125  IF (incx.EQ.incy.AND.incx.GT.0) THEN
126 *
127  nsteps = n*incx
128  IF (dflag.LT.zero) THEN
129  dh11 = dparam(2)
130  dh12 = dparam(4)
131  dh21 = dparam(3)
132  dh22 = dparam(5)
133  DO i = 1,nsteps,incx
134  w = dx(i)
135  z = dy(i)
136  dx(i) = w*dh11 + z*dh12
137  dy(i) = w*dh21 + z*dh22
138  END DO
139  ELSE IF (dflag.EQ.zero) THEN
140  dh12 = dparam(4)
141  dh21 = dparam(3)
142  DO i = 1,nsteps,incx
143  w = dx(i)
144  z = dy(i)
145  dx(i) = w + z*dh12
146  dy(i) = w*dh21 + z
147  END DO
148  ELSE
149  dh11 = dparam(2)
150  dh22 = dparam(5)
151  DO i = 1,nsteps,incx
152  w = dx(i)
153  z = dy(i)
154  dx(i) = w*dh11 + z
155  dy(i) = -w + dh22*z
156  END DO
157  END IF
158  ELSE
159  kx = 1
160  ky = 1
161  IF (incx.LT.0) kx = 1 + (1-n)*incx
162  IF (incy.LT.0) ky = 1 + (1-n)*incy
163 *
164  IF (dflag.LT.zero) THEN
165  dh11 = dparam(2)
166  dh12 = dparam(4)
167  dh21 = dparam(3)
168  dh22 = dparam(5)
169  DO i = 1,n
170  w = dx(kx)
171  z = dy(ky)
172  dx(kx) = w*dh11 + z*dh12
173  dy(ky) = w*dh21 + z*dh22
174  kx = kx + incx
175  ky = ky + incy
176  END DO
177  ELSE IF (dflag.EQ.zero) THEN
178  dh12 = dparam(4)
179  dh21 = dparam(3)
180  DO i = 1,n
181  w = dx(kx)
182  z = dy(ky)
183  dx(kx) = w + z*dh12
184  dy(ky) = w*dh21 + z
185  kx = kx + incx
186  ky = ky + incy
187  END DO
188  ELSE
189  dh11 = dparam(2)
190  dh22 = dparam(5)
191  DO i = 1,n
192  w = dx(kx)
193  z = dy(ky)
194  dx(kx) = w*dh11 + z
195  dy(ky) = -w + dh22*z
196  kx = kx + incx
197  ky = ky + incy
198  END DO
199  END IF
200  END IF
201  RETURN

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