 LAPACK  3.6.1 LAPACK: Linear Algebra PACKage
 double precision function ddot ( integer N, double precision, dimension(*) DX, integer INCX, double precision, dimension(*) DY, integer INCY )

DDOT

Purpose:
```    DDOT forms the dot product of two vectors.
uses unrolled loops for increments equal to one.```
Date
November 2011
Further Details:
```     jack dongarra, linpack, 3/11/78.
modified 12/3/93, array(1) declarations changed to array(*)```

Definition at line 53 of file ddot.f.

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 *
59 * .. Scalar Arguments ..
60  INTEGER incx,incy,n
61 * ..
62 * .. Array Arguments ..
63  DOUBLE PRECISION dx(*),dy(*)
64 * ..
65 *
66 * =====================================================================
67 *
68 * .. Local Scalars ..
69  DOUBLE PRECISION dtemp
70  INTEGER i,ix,iy,m,mp1
71 * ..
72 * .. Intrinsic Functions ..
73  INTRINSIC mod
74 * ..
75  ddot = 0.0d0
76  dtemp = 0.0d0
77  IF (n.LE.0) RETURN
78  IF (incx.EQ.1 .AND. incy.EQ.1) THEN
79 *
80 * code for both increments equal to 1
81 *
82 *
83 * clean-up loop
84 *
85  m = mod(n,5)
86  IF (m.NE.0) THEN
87  DO i = 1,m
88  dtemp = dtemp + dx(i)*dy(i)
89  END DO
90  IF (n.LT.5) THEN
91  ddot=dtemp
92  RETURN
93  END IF
94  END IF
95  mp1 = m + 1
96  DO i = mp1,n,5
97  dtemp = dtemp + dx(i)*dy(i) + dx(i+1)*dy(i+1) +
98  \$ dx(i+2)*dy(i+2) + dx(i+3)*dy(i+3) + dx(i+4)*dy(i+4)
99  END DO
100  ELSE
101 *
102 * code for unequal increments or equal increments
103 * not equal to 1
104 *
105  ix = 1
106  iy = 1
107  IF (incx.LT.0) ix = (-n+1)*incx + 1
108  IF (incy.LT.0) iy = (-n+1)*incy + 1
109  DO i = 1,n
110  dtemp = dtemp + dx(ix)*dy(iy)
111  ix = ix + incx
112  iy = iy + incy
113  END DO
114  END IF
115  ddot = dtemp
116  RETURN
double precision function ddot(N, DX, INCX, DY, INCY)
DDOT
Definition: ddot.f:53

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