Annotation of rpl/lapack/blas/izamax.f, revision 1.14
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: *
29: * Authors:
30: * ========
31: *
1.14 ! bertrand 32: *> \author Univ. of Tennessee
! 33: *> \author Univ. of California Berkeley
! 34: *> \author Univ. of Colorado Denver
! 35: *> \author NAG Ltd.
1.8 bertrand 36: *
1.14 ! bertrand 37: *> \date December 2016
1.8 bertrand 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: * =====================================================================
1.1 bertrand 52: INTEGER FUNCTION IZAMAX(N,ZX,INCX)
1.8 bertrand 53: *
1.14 ! bertrand 54: * -- Reference BLAS level1 routine (version 3.7.0) --
1.8 bertrand 55: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
56: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.14 ! bertrand 57: * December 2016
1.8 bertrand 58: *
1.1 bertrand 59: * .. Scalar Arguments ..
60: INTEGER INCX,N
61: * ..
62: * .. Array Arguments ..
1.8 bertrand 63: COMPLEX*16 ZX(*)
1.1 bertrand 64: * ..
65: *
66: * =====================================================================
67: *
68: * .. Local Scalars ..
1.7 bertrand 69: DOUBLE PRECISION DMAX
1.1 bertrand 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
1.7 bertrand 80: IF (INCX.EQ.1) THEN
1.1 bertrand 81: *
1.7 bertrand 82: * code for increment equal to 1
1.1 bertrand 83: *
1.7 bertrand 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
1.1 bertrand 92: *
1.7 bertrand 93: * code for increment not equal to 1
1.1 bertrand 94: *
1.7 bertrand 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
1.1 bertrand 106: RETURN
107: END
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