Annotation of rpl/lapack/blas/izamax.f, revision 1.18
1.8 bertrand 1: *> \brief \b IZAMAX
2: *
3: * =========== DOCUMENTATION ===========
4: *
1.14 bertrand 5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
1.8 bertrand 7: *
8: * Definition:
9: * ===========
10: *
11: * INTEGER FUNCTION IZAMAX(N,ZX,INCX)
1.14 bertrand 12: *
1.8 bertrand 13: * .. Scalar Arguments ..
14: * INTEGER INCX,N
15: * ..
16: * .. Array Arguments ..
17: * COMPLEX*16 ZX(*)
18: * ..
1.14 bertrand 19: *
1.8 bertrand 20: *
21: *> \par Purpose:
22: * =============
23: *>
24: *> \verbatim
25: *>
1.12 bertrand 26: *> IZAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)|
1.8 bertrand 27: *> \endverbatim
28: *
1.15 bertrand 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] ZX
39: *> \verbatim
40: *> ZX is COMPLEX*16 array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
41: *> \endverbatim
42: *>
43: *> \param[in] INCX
44: *> \verbatim
45: *> INCX is INTEGER
1.17 bertrand 46: *> storage spacing between elements of ZX
1.15 bertrand 47: *> \endverbatim
48: *
1.8 bertrand 49: * Authors:
50: * ========
51: *
1.14 bertrand 52: *> \author Univ. of Tennessee
53: *> \author Univ. of California Berkeley
54: *> \author Univ. of Colorado Denver
55: *> \author NAG Ltd.
1.8 bertrand 56: *
57: *> \ingroup aux_blas
58: *
59: *> \par Further Details:
60: * =====================
61: *>
62: *> \verbatim
63: *>
64: *> jack dongarra, 1/15/85.
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: * =====================================================================
1.1 bertrand 70: INTEGER FUNCTION IZAMAX(N,ZX,INCX)
1.8 bertrand 71: *
1.18 ! bertrand 72: * -- Reference BLAS level1 routine --
1.8 bertrand 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: *
1.1 bertrand 76: * .. Scalar Arguments ..
77: INTEGER INCX,N
78: * ..
79: * .. Array Arguments ..
1.8 bertrand 80: COMPLEX*16 ZX(*)
1.1 bertrand 81: * ..
82: *
83: * =====================================================================
84: *
85: * .. Local Scalars ..
1.7 bertrand 86: DOUBLE PRECISION DMAX
1.1 bertrand 87: INTEGER I,IX
88: * ..
89: * .. External Functions ..
90: DOUBLE PRECISION DCABS1
91: EXTERNAL DCABS1
92: * ..
93: IZAMAX = 0
94: IF (N.LT.1 .OR. INCX.LE.0) RETURN
95: IZAMAX = 1
96: IF (N.EQ.1) RETURN
1.7 bertrand 97: IF (INCX.EQ.1) THEN
1.1 bertrand 98: *
1.7 bertrand 99: * code for increment equal to 1
1.1 bertrand 100: *
1.7 bertrand 101: DMAX = DCABS1(ZX(1))
102: DO I = 2,N
103: IF (DCABS1(ZX(I)).GT.DMAX) THEN
104: IZAMAX = I
105: DMAX = DCABS1(ZX(I))
106: END IF
107: END DO
108: ELSE
1.1 bertrand 109: *
1.7 bertrand 110: * code for increment not equal to 1
1.1 bertrand 111: *
1.7 bertrand 112: IX = 1
113: DMAX = DCABS1(ZX(1))
114: IX = IX + INCX
115: DO I = 2,N
116: IF (DCABS1(ZX(IX)).GT.DMAX) THEN
117: IZAMAX = I
118: DMAX = DCABS1(ZX(IX))
119: END IF
120: IX = IX + INCX
121: END DO
122: END IF
1.1 bertrand 123: RETURN
1.18 ! bertrand 124: *
! 125: * End of IZAMAX
! 126: *
1.1 bertrand 127: END
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