Annotation of rpl/lapack/blas/idamax.f, revision 1.10
1.8 bertrand 1: *> \brief \b IDAMAX
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 IDAMAX(N,DX,INCX)
12: *
13: * .. Scalar Arguments ..
14: * INTEGER INCX,N
15: * ..
16: * .. Array Arguments ..
17: * DOUBLE PRECISION DX(*)
18: * ..
19: *
20: *
21: *> \par Purpose:
22: * =============
23: *>
24: *> \verbatim
25: *>
26: *> IDAMAX 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, linpack, 3/11/78.
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 IDAMAX(N,DX,INCX)
1.8 bertrand 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: *
1.1 bertrand 59: * .. Scalar Arguments ..
60: INTEGER INCX,N
61: * ..
62: * .. Array Arguments ..
63: DOUBLE PRECISION DX(*)
64: * ..
65: *
66: * =====================================================================
67: *
68: * .. Local Scalars ..
69: DOUBLE PRECISION DMAX
70: INTEGER I,IX
71: * ..
72: * .. Intrinsic Functions ..
73: INTRINSIC DABS
74: * ..
75: IDAMAX = 0
76: IF (N.LT.1 .OR. INCX.LE.0) RETURN
77: IDAMAX = 1
78: IF (N.EQ.1) RETURN
1.7 bertrand 79: IF (INCX.EQ.1) THEN
1.1 bertrand 80: *
1.7 bertrand 81: * code for increment equal to 1
1.1 bertrand 82: *
1.7 bertrand 83: DMAX = DABS(DX(1))
84: DO I = 2,N
85: IF (DABS(DX(I)).GT.DMAX) THEN
86: IDAMAX = I
87: DMAX = DABS(DX(I))
88: END IF
89: END DO
90: ELSE
1.1 bertrand 91: *
1.7 bertrand 92: * code for increment not equal to 1
1.1 bertrand 93: *
1.7 bertrand 94: IX = 1
95: DMAX = DABS(DX(1))
96: IX = IX + INCX
97: DO I = 2,N
98: IF (DABS(DX(IX)).GT.DMAX) THEN
99: IDAMAX = I
100: DMAX = DABS(DX(IX))
101: END IF
102: IX = IX + INCX
103: END DO
104: END IF
1.1 bertrand 105: RETURN
106: END
CVSweb interface <joel.bertrand@systella.fr>