1: *> \brief \b IZAMAX
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 IZAMAX(N,ZX,INCX)
12: *
13: * .. Scalar Arguments ..
14: * INTEGER INCX,N
15: * ..
16: * .. Array Arguments ..
17: * COMPLEX*16 ZX(*)
18: * ..
19: *
20: *
21: *> \par Purpose:
22: * =============
23: *>
24: *> \verbatim
25: *>
26: *> IZAMAX finds the index of element having max. absolute value.
27: *> \endverbatim
28: *
29: * Authors:
30: * ========
31: *
32: *> \author Univ. of Tennessee
33: *> \author Univ. of California Berkeley
34: *> \author Univ. of Colorado Denver
35: *> \author NAG Ltd.
36: *
37: *> \date November 2011
38: *
39: *> \ingroup aux_blas
40: *
41: *> \par Further Details:
42: * =====================
43: *>
44: *> \verbatim
45: *>
46: *> jack dongarra, 1/15/85.
47: *> modified 3/93 to return if incx .le. 0.
48: *> modified 12/3/93, array(1) declarations changed to array(*)
49: *> \endverbatim
50: *>
51: * =====================================================================
52: INTEGER FUNCTION IZAMAX(N,ZX,INCX)
53: *
54: * -- Reference BLAS level1 routine (version 3.4.0) --
55: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
56: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
57: * November 2011
58: *
59: * .. Scalar Arguments ..
60: INTEGER INCX,N
61: * ..
62: * .. Array Arguments ..
63: COMPLEX*16 ZX(*)
64: * ..
65: *
66: * =====================================================================
67: *
68: * .. Local Scalars ..
69: DOUBLE PRECISION DMAX
70: INTEGER I,IX
71: * ..
72: * .. External Functions ..
73: DOUBLE PRECISION DCABS1
74: EXTERNAL DCABS1
75: * ..
76: IZAMAX = 0
77: IF (N.LT.1 .OR. INCX.LE.0) RETURN
78: IZAMAX = 1
79: IF (N.EQ.1) RETURN
80: IF (INCX.EQ.1) THEN
81: *
82: * code for increment equal to 1
83: *
84: DMAX = DCABS1(ZX(1))
85: DO I = 2,N
86: IF (DCABS1(ZX(I)).GT.DMAX) THEN
87: IZAMAX = I
88: DMAX = DCABS1(ZX(I))
89: END IF
90: END DO
91: ELSE
92: *
93: * code for increment not equal to 1
94: *
95: IX = 1
96: DMAX = DCABS1(ZX(1))
97: IX = IX + INCX
98: DO I = 2,N
99: IF (DCABS1(ZX(IX)).GT.DMAX) THEN
100: IZAMAX = I
101: DMAX = DCABS1(ZX(IX))
102: END IF
103: IX = IX + INCX
104: END DO
105: END IF
106: RETURN
107: END
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