1: *> \brief \b IZMAX1 finds the index of the vector element whose real part has maximum absolute value.
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download IZMAX1 + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/izmax1.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/izmax1.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/izmax1.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * INTEGER FUNCTION IZMAX1( N, CX, INCX )
22: *
23: * .. Scalar Arguments ..
24: * INTEGER INCX, N
25: * ..
26: * .. Array Arguments ..
27: * COMPLEX*16 CX( * )
28: * ..
29: *
30: *
31: *> \par Purpose:
32: * =============
33: *>
34: *> \verbatim
35: *>
36: *> IZMAX1 finds the index of the element whose real part has maximum
37: *> absolute value.
38: *>
39: *> Based on IZAMAX from Level 1 BLAS.
40: *> The change is to use the 'genuine' absolute value.
41: *> \endverbatim
42: *
43: * Arguments:
44: * ==========
45: *
46: *> \param[in] N
47: *> \verbatim
48: *> N is INTEGER
49: *> The number of elements in the vector CX.
50: *> \endverbatim
51: *>
52: *> \param[in] CX
53: *> \verbatim
54: *> CX is COMPLEX*16 array, dimension (N)
55: *> The vector whose elements will be summed.
56: *> \endverbatim
57: *>
58: *> \param[in] INCX
59: *> \verbatim
60: *> INCX is INTEGER
61: *> The spacing between successive values of CX. INCX >= 1.
62: *> \endverbatim
63: *
64: * Authors:
65: * ========
66: *
67: *> \author Univ. of Tennessee
68: *> \author Univ. of California Berkeley
69: *> \author Univ. of Colorado Denver
70: *> \author NAG Ltd.
71: *
72: *> \date September 2012
73: *
74: *> \ingroup complex16OTHERauxiliary
75: *
76: *> \par Contributors:
77: * ==================
78: *>
79: *> Nick Higham for use with ZLACON.
80: *
81: * =====================================================================
82: INTEGER FUNCTION IZMAX1( N, CX, INCX )
83: *
84: * -- LAPACK auxiliary routine (version 3.4.2) --
85: * -- LAPACK is a software package provided by Univ. of Tennessee, --
86: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
87: * September 2012
88: *
89: * .. Scalar Arguments ..
90: INTEGER INCX, N
91: * ..
92: * .. Array Arguments ..
93: COMPLEX*16 CX( * )
94: * ..
95: *
96: * =====================================================================
97: *
98: * .. Local Scalars ..
99: INTEGER I, IX
100: DOUBLE PRECISION SMAX
101: COMPLEX*16 ZDUM
102: * ..
103: * .. Intrinsic Functions ..
104: INTRINSIC ABS
105: * ..
106: * .. Statement Functions ..
107: DOUBLE PRECISION CABS1
108: * ..
109: * .. Statement Function definitions ..
110: *
111: * NEXT LINE IS THE ONLY MODIFICATION.
112: CABS1( ZDUM ) = ABS( ZDUM )
113: * ..
114: * .. Executable Statements ..
115: *
116: IZMAX1 = 0
117: IF( N.LT.1 )
118: $ RETURN
119: IZMAX1 = 1
120: IF( N.EQ.1 )
121: $ RETURN
122: IF( INCX.EQ.1 )
123: $ GO TO 30
124: *
125: * CODE FOR INCREMENT NOT EQUAL TO 1
126: *
127: IX = 1
128: SMAX = CABS1( CX( 1 ) )
129: IX = IX + INCX
130: DO 20 I = 2, N
131: IF( CABS1( CX( IX ) ).LE.SMAX )
132: $ GO TO 10
133: IZMAX1 = I
134: SMAX = CABS1( CX( IX ) )
135: 10 CONTINUE
136: IX = IX + INCX
137: 20 CONTINUE
138: RETURN
139: *
140: * CODE FOR INCREMENT EQUAL TO 1
141: *
142: 30 CONTINUE
143: SMAX = CABS1( CX( 1 ) )
144: DO 40 I = 2, N
145: IF( CABS1( CX( I ) ).LE.SMAX )
146: $ GO TO 40
147: IZMAX1 = I
148: SMAX = CABS1( CX( I ) )
149: 40 CONTINUE
150: RETURN
151: *
152: * End of IZMAX1
153: *
154: END
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