LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ dasum()

double precision function dasum ( integer  N,
double precision, dimension(*)  DX,
integer  INCX 
)

DASUM

Purpose:
    DASUM takes the sum of the absolute values.
Parameters
[in]N
          N is INTEGER
         number of elements in input vector(s)
[in]DX
          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
[in]INCX
          INCX is INTEGER
         storage spacing between elements of DX
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
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 70 of file dasum.f.

71 *
72 * -- Reference BLAS level1 routine --
73 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
74 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
75 *
76 * .. Scalar Arguments ..
77  INTEGER INCX,N
78 * ..
79 * .. Array Arguments ..
80  DOUBLE PRECISION DX(*)
81 * ..
82 *
83 * =====================================================================
84 *
85 * .. Local Scalars ..
86  DOUBLE PRECISION DTEMP
87  INTEGER I,M,MP1,NINCX
88 * ..
89 * .. Intrinsic Functions ..
90  INTRINSIC dabs,mod
91 * ..
92  dasum = 0.0d0
93  dtemp = 0.0d0
94  IF (n.LE.0 .OR. incx.LE.0) RETURN
95  IF (incx.EQ.1) THEN
96 * code for increment equal to 1
97 *
98 *
99 * clean-up loop
100 *
101  m = mod(n,6)
102  IF (m.NE.0) THEN
103  DO i = 1,m
104  dtemp = dtemp + dabs(dx(i))
105  END DO
106  IF (n.LT.6) THEN
107  dasum = dtemp
108  RETURN
109  END IF
110  END IF
111  mp1 = m + 1
112  DO i = mp1,n,6
113  dtemp = dtemp + dabs(dx(i)) + dabs(dx(i+1)) +
114  $ dabs(dx(i+2)) + dabs(dx(i+3)) +
115  $ dabs(dx(i+4)) + dabs(dx(i+5))
116  END DO
117  ELSE
118 *
119 * code for increment not equal to 1
120 *
121  nincx = n*incx
122  DO i = 1,nincx,incx
123  dtemp = dtemp + dabs(dx(i))
124  END DO
125  END IF
126  dasum = dtemp
127  RETURN
128 *
129 * End of DASUM
130 *
double precision function dasum(N, DX, INCX)
DASUM
Definition: dasum.f:71
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