LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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idamax.f
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1*> \brief \b IDAMAX
2*
3* =========== DOCUMENTATION ===========
4*
5* Online html documentation available at
6* http://www.netlib.org/lapack/explore-html/
7*
8* Definition:
9* ===========
10*
11* INTEGER FUNCTION IDAMAX(N,DX,INCX)
12*
13* .. Scalar Arguments ..
14* INTEGER INCX,N
15* ..
16* .. Array Arguments ..
17* DOUBLE PRECISION DX(*)
18* ..
19*
20*
21*> \par Purpose:
22* =============
23*>
24*> \verbatim
25*>
26*> IDAMAX finds the index of the first element having maximum absolute value.
27*> \endverbatim
28*
29* Arguments:
30* ==========
31*
32*> \param[in] N
33*> \verbatim
34*> N is INTEGER
35*> number of elements in input vector(s)
36*> \endverbatim
37*>
38*> \param[in] DX
39*> \verbatim
40*> DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
41*> \endverbatim
42*>
43*> \param[in] INCX
44*> \verbatim
45*> INCX is INTEGER
46*> storage spacing between elements of DX
47*> \endverbatim
48*
49* Authors:
50* ========
51*
52*> \author Univ. of Tennessee
53*> \author Univ. of California Berkeley
54*> \author Univ. of Colorado Denver
55*> \author NAG Ltd.
56*
57*> \ingroup iamax
58*
59*> \par Further Details:
60* =====================
61*>
62*> \verbatim
63*>
64*> jack dongarra, linpack, 3/11/78.
65*> modified 3/93 to return if incx .le. 0.
66*> modified 12/3/93, array(1) declarations changed to array(*)
67*> \endverbatim
68*>
69* =====================================================================
70 INTEGER FUNCTION idamax(N,DX,INCX)
71*
72* -- Reference BLAS level1 routine --
73* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
74* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
75*
76* .. Scalar Arguments ..
77 INTEGER incx,n
78* ..
79* .. Array Arguments ..
80 DOUBLE PRECISION dx(*)
81* ..
82*
83* =====================================================================
84*
85* .. Local Scalars ..
86 DOUBLE PRECISION dmax
87 INTEGER i,ix
88* ..
89* .. Intrinsic Functions ..
90 INTRINSIC dabs
91* ..
92 idamax = 0
93 IF (n.LT.1 .OR. incx.LE.0) RETURN
94 idamax = 1
95 IF (n.EQ.1) RETURN
96 IF (incx.EQ.1) THEN
97*
98* code for increment equal to 1
99*
100 dmax = dabs(dx(1))
101 DO i = 2,n
102 IF (dabs(dx(i)).GT.dmax) THEN
103 idamax = i
104 dmax = dabs(dx(i))
105 END IF
106 END DO
107 ELSE
108*
109* code for increment not equal to 1
110*
111 ix = 1
112 dmax = dabs(dx(1))
113 ix = ix + incx
114 DO i = 2,n
115 IF (dabs(dx(ix)).GT.dmax) THEN
116 idamax = i
117 dmax = dabs(dx(ix))
118 END IF
119 ix = ix + incx
120 END DO
121 END IF
122 RETURN
123*
124* End of IDAMAX
125*
126 END
integer function idamax(n, dx, incx)
IDAMAX
Definition idamax.f:71