LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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dscal.f
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1*> \brief \b DSCAL
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 DSCAL(N,DA,DX,INCX)
12*
13* .. Scalar Arguments ..
14* DOUBLE PRECISION DA
15* INTEGER INCX,N
16* ..
17* .. Array Arguments ..
18* DOUBLE PRECISION DX(*)
19* ..
20*
21*
22*> \par Purpose:
23* =============
24*>
25*> \verbatim
26*>
27*> DSCAL scales a vector by a constant.
28*> uses unrolled loops for increment equal to 1.
29*> \endverbatim
30*
31* Arguments:
32* ==========
33*
34*> \param[in] N
35*> \verbatim
36*> N is INTEGER
37*> number of elements in input vector(s)
38*> \endverbatim
39*>
40*> \param[in] DA
41*> \verbatim
42*> DA is DOUBLE PRECISION
43*> On entry, DA specifies the scalar alpha.
44*> \endverbatim
45*>
46*> \param[in,out] DX
47*> \verbatim
48*> DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
49*> \endverbatim
50*>
51*> \param[in] INCX
52*> \verbatim
53*> INCX is INTEGER
54*> storage spacing between elements of DX
55*> \endverbatim
56*
57* Authors:
58* ========
59*
60*> \author Univ. of Tennessee
61*> \author Univ. of California Berkeley
62*> \author Univ. of Colorado Denver
63*> \author NAG Ltd.
64*
65*> \ingroup scal
66*
67*> \par Further Details:
68* =====================
69*>
70*> \verbatim
71*>
72*> jack dongarra, linpack, 3/11/78.
73*> modified 3/93 to return if incx .le. 0.
74*> modified 12/3/93, array(1) declarations changed to array(*)
75*> \endverbatim
76*>
77* =====================================================================
78 SUBROUTINE dscal(N,DA,DX,INCX)
79*
80* -- Reference BLAS level1 routine --
81* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
82* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
83*
84* .. Scalar Arguments ..
85 DOUBLE PRECISION DA
86 INTEGER INCX,N
87* ..
88* .. Array Arguments ..
89 DOUBLE PRECISION DX(*)
90* ..
91*
92* =====================================================================
93*
94* .. Local Scalars ..
95 INTEGER I,M,MP1,NINCX
96* .. Parameters ..
97 DOUBLE PRECISION ONE
98 parameter(one=1.0d+0)
99* ..
100* .. Intrinsic Functions ..
101 INTRINSIC mod
102* ..
103 IF (n.LE.0 .OR. incx.LE.0 .OR. da.EQ.one) RETURN
104 IF (incx.EQ.1) THEN
105*
106* code for increment equal to 1
107*
108*
109* clean-up loop
110*
111 m = mod(n,5)
112 IF (m.NE.0) THEN
113 DO i = 1,m
114 dx(i) = da*dx(i)
115 END DO
116 IF (n.LT.5) RETURN
117 END IF
118 mp1 = m + 1
119 DO i = mp1,n,5
120 dx(i) = da*dx(i)
121 dx(i+1) = da*dx(i+1)
122 dx(i+2) = da*dx(i+2)
123 dx(i+3) = da*dx(i+3)
124 dx(i+4) = da*dx(i+4)
125 END DO
126 ELSE
127*
128* code for increment not equal to 1
129*
130 nincx = n*incx
131 DO i = 1,nincx,incx
132 dx(i) = da*dx(i)
133 END DO
134 END IF
135 RETURN
136*
137* End of DSCAL
138*
139 END
subroutine dscal(n, da, dx, incx)
DSCAL
Definition dscal.f:79