LAPACK  3.10.0
LAPACK: Linear Algebra PACKage
sdot.f
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1 *> \brief \b SDOT
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 * Definition:
9 * ===========
10 *
11 * REAL FUNCTION SDOT(N,SX,INCX,SY,INCY)
12 *
13 * .. Scalar Arguments ..
14 * INTEGER INCX,INCY,N
15 * ..
16 * .. Array Arguments ..
17 * REAL SX(*),SY(*)
18 * ..
19 *
20 *
21 *> \par Purpose:
22 * =============
23 *>
24 *> \verbatim
25 *>
26 *> SDOT forms the dot product of two vectors.
27 *> uses unrolled loops for increments equal to one.
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] SX
40 *> \verbatim
41 *> SX is REAL 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 SX
48 *> \endverbatim
49 *>
50 *> \param[in] SY
51 *> \verbatim
52 *> SY is REAL 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 SY
59 *> \endverbatim
60 *
61 * Authors:
62 * ========
63 *
64 *> \author Univ. of Tennessee
65 *> \author Univ. of California Berkeley
66 *> \author Univ. of Colorado Denver
67 *> \author NAG Ltd.
68 *
69 *> \ingroup single_blas_level1
70 *
71 *> \par Further Details:
72 * =====================
73 *>
74 *> \verbatim
75 *>
76 *> jack dongarra, linpack, 3/11/78.
77 *> modified 12/3/93, array(1) declarations changed to array(*)
78 *> \endverbatim
79 *>
80 * =====================================================================
81  REAL function sdot(n,sx,incx,sy,incy)
82 *
83 * -- Reference BLAS level1 routine --
84 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
85 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
86 *
87 * .. Scalar Arguments ..
88  INTEGER incx,incy,n
89 * ..
90 * .. Array Arguments ..
91  REAL sx(*),sy(*)
92 * ..
93 *
94 * =====================================================================
95 *
96 * .. Local Scalars ..
97  REAL stemp
98  INTEGER i,ix,iy,m,mp1
99 * ..
100 * .. Intrinsic Functions ..
101  INTRINSIC mod
102 * ..
103  stemp = 0.0e0
104  sdot = 0.0e0
105  IF (n.LE.0) RETURN
106  IF (incx.EQ.1 .AND. incy.EQ.1) THEN
107 *
108 * code for both increments equal to 1
109 *
110 *
111 * clean-up loop
112 *
113  m = mod(n,5)
114  IF (m.NE.0) THEN
115  DO i = 1,m
116  stemp = stemp + sx(i)*sy(i)
117  END DO
118  IF (n.LT.5) THEN
119  sdot=stemp
120  RETURN
121  END IF
122  END IF
123  mp1 = m + 1
124  DO i = mp1,n,5
125  stemp = stemp + sx(i)*sy(i) + sx(i+1)*sy(i+1) +
126  $ sx(i+2)*sy(i+2) + sx(i+3)*sy(i+3) + sx(i+4)*sy(i+4)
127  END DO
128  ELSE
129 *
130 * code for unequal increments or equal increments
131 * not equal to 1
132 *
133  ix = 1
134  iy = 1
135  IF (incx.LT.0) ix = (-n+1)*incx + 1
136  IF (incy.LT.0) iy = (-n+1)*incy + 1
137  DO i = 1,n
138  stemp = stemp + sx(ix)*sy(iy)
139  ix = ix + incx
140  iy = iy + incy
141  END DO
142  END IF
143  sdot = stemp
144  RETURN
145 *
146 * End of SDOT
147 *
148  END
real function sdot(N, SX, INCX, SY, INCY)
SDOT
Definition: sdot.f:82