1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
*> \brief \b SAXPY
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE SAXPY(N,SA,SX,INCX,SY,INCY)
*
* .. Scalar Arguments ..
* REAL SA
* INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
* REAL SX(*),SY(*)
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> SAXPY constant times a vector plus a vector.
*> uses unrolled loops for increments equal to one.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> number of elements in input vector(s)
*> \endverbatim
*>
*> \param[in] SA
*> \verbatim
*> SA is REAL
*> On entry, SA specifies the scalar alpha.
*> \endverbatim
*>
*> \param[in] SX
*> \verbatim
*> SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*> INCX is INTEGER
*> storage spacing between elements of SX
*> \endverbatim
*>
*> \param[in,out] SY
*> \verbatim
*> SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*> INCY is INTEGER
*> storage spacing between elements of SY
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup axpy
*
*> \par Further Details:
* =====================
*>
*> \verbatim
*>
*> jack dongarra, linpack, 3/11/78.
*> modified 12/3/93, array(1) declarations changed to array(*)
*> \endverbatim
*>
* =====================================================================
SUBROUTINE SAXPY(N,SA,SX,INCX,SY,INCY)
*
* -- Reference BLAS level1 routine --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
REAL SA
INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
REAL SX(*),SY(*)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I,IX,IY,M,MP1
* ..
* .. Intrinsic Functions ..
INTRINSIC MOD
* ..
IF (N.LE.0) RETURN
IF (SA.EQ.0.0) RETURN
IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
*
* code for both increments equal to 1
*
*
* clean-up loop
*
M = MOD(N,4)
IF (M.NE.0) THEN
DO I = 1,M
SY(I) = SY(I) + SA*SX(I)
END DO
END IF
IF (N.LT.4) RETURN
MP1 = M + 1
DO I = MP1,N,4
SY(I) = SY(I) + SA*SX(I)
SY(I+1) = SY(I+1) + SA*SX(I+1)
SY(I+2) = SY(I+2) + SA*SX(I+2)
SY(I+3) = SY(I+3) + SA*SX(I+3)
END DO
ELSE
*
* code for unequal increments or equal increments
* not equal to 1
*
IX = 1
IY = 1
IF (INCX.LT.0) IX = (-N+1)*INCX + 1
IF (INCY.LT.0) IY = (-N+1)*INCY + 1
DO I = 1,N
SY(IY) = SY(IY) + SA*SX(IX)
IX = IX + INCX
IY = IY + INCY
END DO
END IF
RETURN
*
* End of SAXPY
*
END
|
