KTH framework for Nek5000 toolboxes; testing version  0.0.1
dswap.f
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1  subroutine dswap (n,dx,incx,dy,incy)
2 c
3 c interchanges two vectors.
4 c uses unrolled loops for increments equal one.
5 c jack dongarra, linpack, 3/11/78.
6 c modified 12/3/93, array(1) declarations changed to array(*)
7 c
8  double precision dx(*),dy(*),dtemp
9  integer i,incx,incy,ix,iy,m,mp1,n
10 c
11  if(n.le.0)return
12  if(incx.eq.1.and.incy.eq.1)go to 20
13 c
14 c code for unequal increments or equal increments not equal
15 c to 1
16 c
17  ix = 1
18  iy = 1
19  if(incx.lt.0)ix = (-n+1)*incx + 1
20  if(incy.lt.0)iy = (-n+1)*incy + 1
21  do 10 i = 1,n
22  dtemp = dx(ix)
23  dx(ix) = dy(iy)
24  dy(iy) = dtemp
25  ix = ix + incx
26  iy = iy + incy
27  10 continue
28  return
29 c
30 c code for both increments equal to 1
31 c
32 c
33 c clean-up loop
34 c
35  20 m = mod(n,3)
36  if( m .eq. 0 ) go to 40
37  do 30 i = 1,m
38  dtemp = dx(i)
39  dx(i) = dy(i)
40  dy(i) = dtemp
41  30 continue
42  if( n .lt. 3 ) return
43  40 mp1 = m + 1
44  do 50 i = mp1,n,3
45  dtemp = dx(i)
46  dx(i) = dy(i)
47  dy(i) = dtemp
48  dtemp = dx(i + 1)
49  dx(i + 1) = dy(i + 1)
50  dy(i + 1) = dtemp
51  dtemp = dx(i + 2)
52  dx(i + 2) = dy(i + 2)
53  dy(i + 2) = dtemp
54  50 continue
55  return
56  end
dswap
subroutine dswap(n, dx, incx, dy, incy)
Definition: dswap.f:2