LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ drot()

subroutine drot ( integer  N,
double precision, dimension(*)  DX,
integer  INCX,
double precision, dimension(*)  DY,
integer  INCY,
double precision  C,
double precision  S 
)

DROT

Purpose:
    DROT applies a plane rotation.
Parameters
[in]N
          N is INTEGER
         number of elements in input vector(s)
[in,out]DX
          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
[in]INCX
          INCX is INTEGER
         storage spacing between elements of DX
[in,out]DY
          DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
[in]INCY
          INCY is INTEGER
         storage spacing between elements of DY
[in]C
          C is DOUBLE PRECISION
[in]S
          S is DOUBLE PRECISION
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Further Details:
     jack dongarra, linpack, 3/11/78.
     modified 12/3/93, array(1) declarations changed to array(*)

Definition at line 91 of file drot.f.

92 *
93 * -- Reference BLAS level1 routine --
94 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
95 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
96 *
97 * .. Scalar Arguments ..
98  DOUBLE PRECISION C,S
99  INTEGER INCX,INCY,N
100 * ..
101 * .. Array Arguments ..
102  DOUBLE PRECISION DX(*),DY(*)
103 * ..
104 *
105 * =====================================================================
106 *
107 * .. Local Scalars ..
108  DOUBLE PRECISION DTEMP
109  INTEGER I,IX,IY
110 * ..
111  IF (n.LE.0) RETURN
112  IF (incx.EQ.1 .AND. incy.EQ.1) THEN
113 *
114 * code for both increments equal to 1
115 *
116  DO i = 1,n
117  dtemp = c*dx(i) + s*dy(i)
118  dy(i) = c*dy(i) - s*dx(i)
119  dx(i) = dtemp
120  END DO
121  ELSE
122 *
123 * code for unequal increments or equal increments not equal
124 * to 1
125 *
126  ix = 1
127  iy = 1
128  IF (incx.LT.0) ix = (-n+1)*incx + 1
129  IF (incy.LT.0) iy = (-n+1)*incy + 1
130  DO i = 1,n
131  dtemp = c*dx(ix) + s*dy(iy)
132  dy(iy) = c*dy(iy) - s*dx(ix)
133  dx(ix) = dtemp
134  ix = ix + incx
135  iy = iy + incy
136  END DO
137  END IF
138  RETURN
139 *
140 * End of DROT
141 *
Here is the caller graph for this function: