LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
 subroutine srotm ( integer N, real, dimension(*) SX, integer INCX, real, dimension(*) SY, integer INCY, real, dimension(5) SPARAM )

SROTM

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

(SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN
(SX**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.```
Parameters
 [in] N ``` N is INTEGER number of elements in input vector(s)``` [in,out] SX ``` SX is REAL array, dimension N double precision vector with N elements``` [in] INCX ``` INCX is INTEGER storage spacing between elements of SX``` [in,out] SY ``` SY is REAL array, dimension N double precision vector with N elements``` [in] INCY ``` INCY is INTEGER storage spacing between elements of SY``` [in,out] SPARAM ``` SPARAM is REAL array, dimension 5 SPARAM(1)=SFLAG SPARAM(2)=SH11 SPARAM(3)=SH21 SPARAM(4)=SH12 SPARAM(5)=SH22```
Date
November 2011

Definition at line 101 of file srotm.f.

101 *
102 * -- Reference BLAS level1 routine (version 3.4.0) --
103 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
104 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
105 * November 2011
106 *
107 * .. Scalar Arguments ..
108  INTEGER incx,incy,n
109 * ..
110 * .. Array Arguments ..
111  REAL sparam(5),sx(*),sy(*)
112 * ..
113 *
114 * =====================================================================
115 *
116 * .. Local Scalars ..
117  REAL sflag,sh11,sh12,sh21,sh22,two,w,z,zero
118  INTEGER i,kx,ky,nsteps
119 * ..
120 * .. Data statements ..
121  DATA zero,two/0.e0,2.e0/
122 * ..
123 *
124  sflag = sparam(1)
125  IF (n.LE.0 .OR. (sflag+two.EQ.zero)) RETURN
126  IF (incx.EQ.incy.AND.incx.GT.0) THEN
127 *
128  nsteps = n*incx
129  IF (sflag.LT.zero) THEN
130  sh11 = sparam(2)
131  sh12 = sparam(4)
132  sh21 = sparam(3)
133  sh22 = sparam(5)
134  DO i = 1,nsteps,incx
135  w = sx(i)
136  z = sy(i)
137  sx(i) = w*sh11 + z*sh12
138  sy(i) = w*sh21 + z*sh22
139  END DO
140  ELSE IF (sflag.EQ.zero) THEN
141  sh12 = sparam(4)
142  sh21 = sparam(3)
143  DO i = 1,nsteps,incx
144  w = sx(i)
145  z = sy(i)
146  sx(i) = w + z*sh12
147  sy(i) = w*sh21 + z
148  END DO
149  ELSE
150  sh11 = sparam(2)
151  sh22 = sparam(5)
152  DO i = 1,nsteps,incx
153  w = sx(i)
154  z = sy(i)
155  sx(i) = w*sh11 + z
156  sy(i) = -w + sh22*z
157  END DO
158  END IF
159  ELSE
160  kx = 1
161  ky = 1
162  IF (incx.LT.0) kx = 1 + (1-n)*incx
163  IF (incy.LT.0) ky = 1 + (1-n)*incy
164 *
165  IF (sflag.LT.zero) THEN
166  sh11 = sparam(2)
167  sh12 = sparam(4)
168  sh21 = sparam(3)
169  sh22 = sparam(5)
170  DO i = 1,n
171  w = sx(kx)
172  z = sy(ky)
173  sx(kx) = w*sh11 + z*sh12
174  sy(ky) = w*sh21 + z*sh22
175  kx = kx + incx
176  ky = ky + incy
177  END DO
178  ELSE IF (sflag.EQ.zero) THEN
179  sh12 = sparam(4)
180  sh21 = sparam(3)
181  DO i = 1,n
182  w = sx(kx)
183  z = sy(ky)
184  sx(kx) = w + z*sh12
185  sy(ky) = w*sh21 + z
186  kx = kx + incx
187  ky = ky + incy
188  END DO
189  ELSE
190  sh11 = sparam(2)
191  sh22 = sparam(5)
192  DO i = 1,n
193  w = sx(kx)
194  z = sy(ky)
195  sx(kx) = w*sh11 + z
196  sy(ky) = -w + sh22*z
197  kx = kx + incx
198  ky = ky + incy
199  END DO
200  END IF
201  END IF
202  RETURN

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