LAPACK  3.5.0
LAPACK: Linear Algebra PACKage
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sasum.f
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1 *> \brief \b SASUM
2 *
3 * =========== DOCUMENTATION ===========
4 *
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
7 *
8 * Definition:
9 * ===========
10 *
11 * REAL FUNCTION SASUM(N,SX,INCX)
12 *
13 * .. Scalar Arguments ..
14 * INTEGER INCX,N
15 * ..
16 * .. Array Arguments ..
17 * REAL SX(*)
18 * ..
19 *
20 *
21 *> \par Purpose:
22 * =============
23 *>
24 *> \verbatim
25 *>
26 *> SASUM takes the sum of the absolute values.
27 *> uses unrolled loops for increment equal to one.
28 *> \endverbatim
29 *
30 * Authors:
31 * ========
32 *
33 *> \author Univ. of Tennessee
34 *> \author Univ. of California Berkeley
35 *> \author Univ. of Colorado Denver
36 *> \author NAG Ltd.
37 *
38 *> \date November 2011
39 *
40 *> \ingroup single_blas_level1
41 *
42 *> \par Further Details:
43 * =====================
44 *>
45 *> \verbatim
46 *>
47 *> jack dongarra, linpack, 3/11/78.
48 *> modified 3/93 to return if incx .le. 0.
49 *> modified 12/3/93, array(1) declarations changed to array(*)
50 *> \endverbatim
51 *>
52 * =====================================================================
53  REAL FUNCTION sasum(N,SX,INCX)
54 *
55 * -- Reference BLAS level1 routine (version 3.4.0) --
56 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
57 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
58 * November 2011
59 *
60 * .. Scalar Arguments ..
61  INTEGER incx,n
62 * ..
63 * .. Array Arguments ..
64  REAL sx(*)
65 * ..
66 *
67 * =====================================================================
68 *
69 * .. Local Scalars ..
70  REAL stemp
71  INTEGER i,m,mp1,nincx
72 * ..
73 * .. Intrinsic Functions ..
74  INTRINSIC abs,mod
75 * ..
76  sasum = 0.0e0
77  stemp = 0.0e0
78  IF (n.LE.0 .OR. incx.LE.0) RETURN
79  IF (incx.EQ.1) THEN
80 * code for increment equal to 1
81 *
82 *
83 * clean-up loop
84 *
85  m = mod(n,6)
86  IF (m.NE.0) THEN
87  DO i = 1,m
88  stemp = stemp + abs(sx(i))
89  END DO
90  IF (n.LT.6) THEN
91  sasum = stemp
92  RETURN
93  END IF
94  END IF
95  mp1 = m + 1
96  DO i = mp1,n,6
97  stemp = stemp + abs(sx(i)) + abs(sx(i+1)) +
98  $ abs(sx(i+2)) + abs(sx(i+3)) +
99  $ abs(sx(i+4)) + abs(sx(i+5))
100  END DO
101  ELSE
102 *
103 * code for increment not equal to 1
104 *
105  nincx = n*incx
106  DO i = 1,nincx,incx
107  stemp = stemp + abs(sx(i))
108  END DO
109  END IF
110  sasum = stemp
111  RETURN
112  END