LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ sdot()

real function sdot ( integer  N,
real, dimension(*)  SX,
integer  INCX,
real, dimension(*)  SY,
integer  INCY 
)

SDOT

Purpose:
    SDOT forms the dot product of two vectors.
    uses unrolled loops for increments equal to one.
Parameters
[in]N
          N is INTEGER
         number of elements in input vector(s)
[in]SX
          SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
[in]INCX
          INCX is INTEGER
         storage spacing between elements of SX
[in]SY
          SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
[in]INCY
          INCY is INTEGER
         storage spacing between elements of SY
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Further Details:
     jack dongarra, linpack, 3/11/78.
     modified 12/3/93, array(1) declarations changed to array(*)

Definition at line 81 of file sdot.f.

82 *
83 * -- Reference BLAS level1 routine --
84 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
85 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
86 *
87 * .. Scalar Arguments ..
88  INTEGER INCX,INCY,N
89 * ..
90 * .. Array Arguments ..
91  REAL SX(*),SY(*)
92 * ..
93 *
94 * =====================================================================
95 *
96 * .. Local Scalars ..
97  REAL STEMP
98  INTEGER I,IX,IY,M,MP1
99 * ..
100 * .. Intrinsic Functions ..
101  INTRINSIC mod
102 * ..
103  stemp = 0.0e0
104  sdot = 0.0e0
105  IF (n.LE.0) RETURN
106  IF (incx.EQ.1 .AND. incy.EQ.1) THEN
107 *
108 * code for both increments equal to 1
109 *
110 *
111 * clean-up loop
112 *
113  m = mod(n,5)
114  IF (m.NE.0) THEN
115  DO i = 1,m
116  stemp = stemp + sx(i)*sy(i)
117  END DO
118  IF (n.LT.5) THEN
119  sdot=stemp
120  RETURN
121  END IF
122  END IF
123  mp1 = m + 1
124  DO i = mp1,n,5
125  stemp = stemp + sx(i)*sy(i) + sx(i+1)*sy(i+1) +
126  $ sx(i+2)*sy(i+2) + sx(i+3)*sy(i+3) + sx(i+4)*sy(i+4)
127  END DO
128  ELSE
129 *
130 * code for unequal increments or equal increments
131 * not equal to 1
132 *
133  ix = 1
134  iy = 1
135  IF (incx.LT.0) ix = (-n+1)*incx + 1
136  IF (incy.LT.0) iy = (-n+1)*incy + 1
137  DO i = 1,n
138  stemp = stemp + sx(ix)*sy(iy)
139  ix = ix + incx
140  iy = iy + incy
141  END DO
142  END IF
143  sdot = stemp
144  RETURN
145 *
146 * End of SDOT
147 *
real function sdot(N, SX, INCX, SY, INCY)
SDOT
Definition: sdot.f:82
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