LAPACK  3.10.0
LAPACK: Linear Algebra PACKage
icamax.f
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1 *> \brief \b ICAMAX
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 ICAMAX(N,CX,INCX)
12 *
13 * .. Scalar Arguments ..
14 * INTEGER INCX,N
15 * ..
16 * .. Array Arguments ..
17 * COMPLEX CX(*)
18 * ..
19 *
20 *
21 *> \par Purpose:
22 * =============
23 *>
24 *> \verbatim
25 *>
26 *> ICAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)|
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] CX
39 *> \verbatim
40 *> CX is COMPLEX 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 CX
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 aux_blas
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 icamax(N,CX,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  COMPLEX cx(*)
81 * ..
82 *
83 * =====================================================================
84 *
85 * .. Local Scalars ..
86  REAL smax
87  INTEGER i,ix
88 * ..
89 * .. External Functions ..
90  REAL scabs1
91  EXTERNAL scabs1
92 * ..
93  icamax = 0
94  IF (n.LT.1 .OR. incx.LE.0) RETURN
95  icamax = 1
96  IF (n.EQ.1) RETURN
97  IF (incx.EQ.1) THEN
98 *
99 * code for increment equal to 1
100 *
101  smax = scabs1(cx(1))
102  DO i = 2,n
103  IF (scabs1(cx(i)).GT.smax) THEN
104  icamax = i
105  smax = scabs1(cx(i))
106  END IF
107  END DO
108  ELSE
109 *
110 * code for increment not equal to 1
111 *
112  ix = 1
113  smax = scabs1(cx(1))
114  ix = ix + incx
115  DO i = 2,n
116  IF (scabs1(cx(ix)).GT.smax) THEN
117  icamax = i
118  smax = scabs1(cx(ix))
119  END IF
120  ix = ix + incx
121  END DO
122  END IF
123  RETURN
124 *
125 * End of ICAMAX
126 *
127  END
integer function icamax(N, CX, INCX)
ICAMAX
Definition: icamax.f:71
real function scabs1(Z)
SCABS1
Definition: scabs1.f:46