1: *> \brief \b DASUM
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: * Definition:
9: * ===========
10: *
11: * DOUBLE PRECISION FUNCTION DASUM(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: *> DASUM takes the sum of the absolute values.
27: *> \endverbatim
28: *
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] DX
39: *> \verbatim
40: *> DX is DOUBLE PRECISION 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 DX
47: *> \endverbatim
48: *
49: * Authors:
50: * ========
51: *
52: *> \author Univ. of Tennessee
53: *> \author Univ. of California Berkeley
54: *> \author Univ. of Colorado Denver
55: *> \author NAG Ltd.
56: *
57: *> \date November 2017
58: *
59: *> \ingroup double_blas_level1
60: *
61: *> \par Further Details:
62: * =====================
63: *>
64: *> \verbatim
65: *>
66: *> jack dongarra, linpack, 3/11/78.
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: * =====================================================================
72: DOUBLE PRECISION FUNCTION DASUM(N,DX,INCX)
73: *
74: * -- Reference BLAS level1 routine (version 3.8.0) --
75: * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
76: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
77: * November 2017
78: *
79: * .. Scalar Arguments ..
80: INTEGER INCX,N
81: * ..
82: * .. Array Arguments ..
83: DOUBLE PRECISION DX(*)
84: * ..
85: *
86: * =====================================================================
87: *
88: * .. Local Scalars ..
89: DOUBLE PRECISION DTEMP
90: INTEGER I,M,MP1,NINCX
91: * ..
92: * .. Intrinsic Functions ..
93: INTRINSIC DABS,MOD
94: * ..
95: DASUM = 0.0d0
96: DTEMP = 0.0d0
97: IF (N.LE.0 .OR. INCX.LE.0) RETURN
98: IF (INCX.EQ.1) THEN
99: * code for increment equal to 1
100: *
101: *
102: * clean-up loop
103: *
104: M = MOD(N,6)
105: IF (M.NE.0) THEN
106: DO I = 1,M
107: DTEMP = DTEMP + DABS(DX(I))
108: END DO
109: IF (N.LT.6) THEN
110: DASUM = DTEMP
111: RETURN
112: END IF
113: END IF
114: MP1 = M + 1
115: DO I = MP1,N,6
116: DTEMP = DTEMP + DABS(DX(I)) + DABS(DX(I+1)) +
117: $ DABS(DX(I+2)) + DABS(DX(I+3)) +
118: $ DABS(DX(I+4)) + DABS(DX(I+5))
119: END DO
120: ELSE
121: *
122: * code for increment not equal to 1
123: *
124: NINCX = N*INCX
125: DO I = 1,NINCX,INCX
126: DTEMP = DTEMP + DABS(DX(I))
127: END DO
128: END IF
129: DASUM = DTEMP
130: RETURN
131: END
CVSweb interface <joel.bertrand@systella.fr>