LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
zrot.f
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1 *> \brief \b ZROT applies a plane rotation with real cosine and complex sine to a pair of complex vectors.
2 *
3 * =========== DOCUMENTATION ===========
4 *
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17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
22 *
23 * .. Scalar Arguments ..
24 * INTEGER INCX, INCY, N
25 * DOUBLE PRECISION C
26 * COMPLEX*16 S
27 * ..
28 * .. Array Arguments ..
29 * COMPLEX*16 CX( * ), CY( * )
30 * ..
31 *
32 *
33 *> \par Purpose:
34 * =============
35 *>
36 *> \verbatim
37 *>
38 *> ZROT applies a plane rotation, where the cos (C) is real and the
39 *> sin (S) is complex, and the vectors CX and CY are complex.
40 *> \endverbatim
41 *
42 * Arguments:
43 * ==========
44 *
45 *> \param[in] N
46 *> \verbatim
47 *> N is INTEGER
48 *> The number of elements in the vectors CX and CY.
49 *> \endverbatim
50 *>
51 *> \param[in,out] CX
52 *> \verbatim
53 *> CX is COMPLEX*16 array, dimension (N)
54 *> On input, the vector X.
55 *> On output, CX is overwritten with C*X + S*Y.
56 *> \endverbatim
57 *>
58 *> \param[in] INCX
59 *> \verbatim
60 *> INCX is INTEGER
61 *> The increment between successive values of CY. INCX <> 0.
62 *> \endverbatim
63 *>
64 *> \param[in,out] CY
65 *> \verbatim
66 *> CY is COMPLEX*16 array, dimension (N)
67 *> On input, the vector Y.
68 *> On output, CY is overwritten with -CONJG(S)*X + C*Y.
69 *> \endverbatim
70 *>
71 *> \param[in] INCY
72 *> \verbatim
73 *> INCY is INTEGER
74 *> The increment between successive values of CY. INCX <> 0.
75 *> \endverbatim
76 *>
77 *> \param[in] C
78 *> \verbatim
79 *> C is DOUBLE PRECISION
80 *> \endverbatim
81 *>
82 *> \param[in] S
83 *> \verbatim
84 *> S is COMPLEX*16
85 *> C and S define a rotation
86 *> [ C S ]
87 *> [ -conjg(S) C ]
88 *> where C*C + S*CONJG(S) = 1.0.
89 *> \endverbatim
90 *
91 * Authors:
92 * ========
93 *
94 *> \author Univ. of Tennessee
95 *> \author Univ. of California Berkeley
96 *> \author Univ. of Colorado Denver
97 *> \author NAG Ltd.
98 *
99 *> \date September 2012
100 *
101 *> \ingroup complex16OTHERauxiliary
102 *
103 * =====================================================================
104  SUBROUTINE zrot( N, CX, INCX, CY, INCY, C, S )
105 *
106 * -- LAPACK auxiliary routine (version 3.4.2) --
107 * -- LAPACK is a software package provided by Univ. of Tennessee, --
108 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
109 * September 2012
110 *
111 * .. Scalar Arguments ..
112  INTEGER INCX, INCY, N
113  DOUBLE PRECISION C
114  COMPLEX*16 S
115 * ..
116 * .. Array Arguments ..
117  COMPLEX*16 CX( * ), CY( * )
118 * ..
119 *
120 * =====================================================================
121 *
122 * .. Local Scalars ..
123  INTEGER I, IX, IY
124  COMPLEX*16 STEMP
125 * ..
126 * .. Intrinsic Functions ..
127  INTRINSIC dconjg
128 * ..
129 * .. Executable Statements ..
130 *
131  IF( n.LE.0 )
132  \$ RETURN
133  IF( incx.EQ.1 .AND. incy.EQ.1 )
134  \$ GO TO 20
135 *
136 * Code for unequal increments or equal increments not equal to 1
137 *
138  ix = 1
139  iy = 1
140  IF( incx.LT.0 )
141  \$ ix = ( -n+1 )*incx + 1
142  IF( incy.LT.0 )
143  \$ iy = ( -n+1 )*incy + 1
144  DO 10 i = 1, n
145  stemp = c*cx( ix ) + s*cy( iy )
146  cy( iy ) = c*cy( iy ) - dconjg( s )*cx( ix )
147  cx( ix ) = stemp
148  ix = ix + incx
149  iy = iy + incy
150  10 CONTINUE
151  RETURN
152 *
153 * Code for both increments equal to 1
154 *
155  20 CONTINUE
156  DO 30 i = 1, n
157  stemp = c*cx( i ) + s*cy( i )
158  cy( i ) = c*cy( i ) - dconjg( s )*cx( i )
159  cx( i ) = stemp
160  30 CONTINUE
161  RETURN
162  END
subroutine zrot(N, CX, INCX, CY, INCY, C, S)
ZROT applies a plane rotation with real cosine and complex sine to a pair of complex vectors...
Definition: zrot.f:105