1: *> \brief \b DROT
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: * Definition:
9: * ===========
10: *
11: * SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
12: *
13: * .. Scalar Arguments ..
14: * DOUBLE PRECISION C,S
15: * INTEGER INCX,INCY,N
16: * ..
17: * .. Array Arguments ..
18: * DOUBLE PRECISION DX(*),DY(*)
19: * ..
20: *
21: *
22: *> \par Purpose:
23: * =============
24: *>
25: *> \verbatim
26: *>
27: *> DROT applies a plane rotation.
28: *> \endverbatim
29: *
30: * Arguments:
31: * ==========
32: *
33: *> \param[in] N
34: *> \verbatim
35: *> N is INTEGER
36: *> number of elements in input vector(s)
37: *> \endverbatim
38: *>
39: *> \param[in,out] DX
40: *> \verbatim
41: *> DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
42: *> \endverbatim
43: *>
44: *> \param[in] INCX
45: *> \verbatim
46: *> INCX is INTEGER
47: *> storage spacing between elements of DX
48: *> \endverbatim
49: *>
50: *> \param[in,out] DY
51: *> \verbatim
52: *> DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
53: *> \endverbatim
54: *>
55: *> \param[in] INCY
56: *> \verbatim
57: *> INCY is INTEGER
58: *> storage spacing between elements of DY
59: *> \endverbatim
60: *>
61: *> \param[in] C
62: *> \verbatim
63: *> C is DOUBLE PRECISION
64: *> \endverbatim
65: *>
66: *> \param[in] S
67: *> \verbatim
68: *> S is DOUBLE PRECISION
69: *> \endverbatim
70: *
71: * Authors:
72: * ========
73: *
74: *> \author Univ. of Tennessee
75: *> \author Univ. of California Berkeley
76: *> \author Univ. of Colorado Denver
77: *> \author NAG Ltd.
78: *
79: *> \date November 2017
80: *
81: *> \ingroup double_blas_level1
82: *
83: *> \par Further Details:
84: * =====================
85: *>
86: *> \verbatim
87: *>
88: *> jack dongarra, linpack, 3/11/78.
89: *> modified 12/3/93, array(1) declarations changed to array(*)
90: *> \endverbatim
91: *>
92: * =====================================================================
93: SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
94: *
95: * -- Reference BLAS level1 routine (version 3.8.0) --
96: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
97: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
98: * November 2017
99: *
100: * .. Scalar Arguments ..
101: DOUBLE PRECISION C,S
102: INTEGER INCX,INCY,N
103: * ..
104: * .. Array Arguments ..
105: DOUBLE PRECISION DX(*),DY(*)
106: * ..
107: *
108: * =====================================================================
109: *
110: * .. Local Scalars ..
111: DOUBLE PRECISION DTEMP
112: INTEGER I,IX,IY
113: * ..
114: IF (N.LE.0) RETURN
115: IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
116: *
117: * code for both increments equal to 1
118: *
119: DO I = 1,N
120: DTEMP = C*DX(I) + S*DY(I)
121: DY(I) = C*DY(I) - S*DX(I)
122: DX(I) = DTEMP
123: END DO
124: ELSE
125: *
126: * code for unequal increments or equal increments not equal
127: * to 1
128: *
129: IX = 1
130: IY = 1
131: IF (INCX.LT.0) IX = (-N+1)*INCX + 1
132: IF (INCY.LT.0) IY = (-N+1)*INCY + 1
133: DO I = 1,N
134: DTEMP = C*DX(IX) + S*DY(IY)
135: DY(IY) = C*DY(IY) - S*DX(IX)
136: DX(IX) = DTEMP
137: IX = IX + INCX
138: IY = IY + INCY
139: END DO
140: END IF
141: RETURN
142: END
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