Annotation of rpl/lapack/blas/izamax.f, revision 1.15
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
! 46: *> storage spacing between elements of SX
! 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: *
1.15 ! bertrand 57: *> \date November 2017
1.8 bertrand 58: *
59: *> \ingroup aux_blas
60: *
61: *> \par Further Details:
62: * =====================
63: *>
64: *> \verbatim
65: *>
66: *> jack dongarra, 1/15/85.
67: *> modified 3/93 to return if incx .le. 0.
68: *> modified 12/3/93, array(1) declarations changed to array(*)
69: *> \endverbatim
70: *>
71: * =====================================================================
1.1 bertrand 72: INTEGER FUNCTION IZAMAX(N,ZX,INCX)
1.8 bertrand 73: *
1.15 ! bertrand 74: * -- Reference BLAS level1 routine (version 3.8.0) --
1.8 bertrand 75: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
76: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.15 ! bertrand 77: * November 2017
1.8 bertrand 78: *
1.1 bertrand 79: * .. Scalar Arguments ..
80: INTEGER INCX,N
81: * ..
82: * .. Array Arguments ..
1.8 bertrand 83: COMPLEX*16 ZX(*)
1.1 bertrand 84: * ..
85: *
86: * =====================================================================
87: *
88: * .. Local Scalars ..
1.7 bertrand 89: DOUBLE PRECISION DMAX
1.1 bertrand 90: INTEGER I,IX
91: * ..
92: * .. External Functions ..
93: DOUBLE PRECISION DCABS1
94: EXTERNAL DCABS1
95: * ..
96: IZAMAX = 0
97: IF (N.LT.1 .OR. INCX.LE.0) RETURN
98: IZAMAX = 1
99: IF (N.EQ.1) RETURN
1.7 bertrand 100: IF (INCX.EQ.1) THEN
1.1 bertrand 101: *
1.7 bertrand 102: * code for increment equal to 1
1.1 bertrand 103: *
1.7 bertrand 104: DMAX = DCABS1(ZX(1))
105: DO I = 2,N
106: IF (DCABS1(ZX(I)).GT.DMAX) THEN
107: IZAMAX = I
108: DMAX = DCABS1(ZX(I))
109: END IF
110: END DO
111: ELSE
1.1 bertrand 112: *
1.7 bertrand 113: * code for increment not equal to 1
1.1 bertrand 114: *
1.7 bertrand 115: IX = 1
116: DMAX = DCABS1(ZX(1))
117: IX = IX + INCX
118: DO I = 2,N
119: IF (DCABS1(ZX(IX)).GT.DMAX) THEN
120: IZAMAX = I
121: DMAX = DCABS1(ZX(IX))
122: END IF
123: IX = IX + INCX
124: END DO
125: END IF
1.1 bertrand 126: RETURN
127: END
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