LAPACK  3.6.0 LAPACK: Linear Algebra PACKage
isamax.f File Reference

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Functions/Subroutines

integer function isamax (N, SX, INCX)
ISAMAX More...

Function/Subroutine Documentation

 integer function isamax ( integer N, real, dimension(*) SX, integer INCX )

ISAMAX

Purpose:
`    ISAMAX finds the index of the first element having maximum absolute value.`
Date
November 2015
Further Details:
```     jack dongarra, linpack, 3/11/78.
modified 3/93 to return if incx .le. 0.
modified 12/3/93, array(1) declarations changed to array(*)```

Definition at line 53 of file isamax.f.

53 *
54 * -- Reference BLAS level1 routine (version 3.6.0) --
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 2015
58 *
59 * .. Scalar Arguments ..
60  INTEGER incx,n
61 * ..
62 * .. Array Arguments ..
63  REAL sx(*)
64 * ..
65 *
66 * =====================================================================
67 *
68 * .. Local Scalars ..
69  REAL smax
70  INTEGER i,ix
71 * ..
72 * .. Intrinsic Functions ..
73  INTRINSIC abs
74 * ..
75  isamax = 0
76  IF (n.LT.1 .OR. incx.LE.0) RETURN
77  isamax = 1
78  IF (n.EQ.1) RETURN
79  IF (incx.EQ.1) THEN
80 *
81 * code for increment equal to 1
82 *
83  smax = abs(sx(1))
84  DO i = 2,n
85  IF (abs(sx(i)).GT.smax) THEN
86  isamax = i
87  smax = abs(sx(i))
88  END IF
89  END DO
90  ELSE
91 *
92 * code for increment not equal to 1
93 *
94  ix = 1
95  smax = abs(sx(1))
96  ix = ix + incx
97  DO i = 2,n
98  IF (abs(sx(ix)).GT.smax) THEN
99  isamax = i
100  smax = abs(sx(ix))
101  END IF
102  ix = ix + incx
103  END DO
104  END IF
105  RETURN
integer function isamax(N, SX, INCX)
ISAMAX
Definition: isamax.f:53

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