share/lapack/blas/fortran/dcopy.f

   1       subroutine  dcopy(n,dx,incx,dy,incy)
   2 c
   3 c     copies a vector, x, to a vector, y.
   4 c     uses unrolled loops for increments equal to 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(*)
   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
  15 c          not equal 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         dy(iy) = dx(ix)
  23         ix = ix + incx
  24         iy = iy + incy
  25    10 continue
  26       return
  27 c
  28 c        code for both increments equal to 1
  29 c
  30 c
  31 c        clean-up loop
  32 c
  33    20 m = mod(n,7)
  34       if( m .eq. 0 ) go to 40
  35       do 30 i = 1,m
  36         dy(i) = dx(i)
  37    30 continue
  38       if( n .lt. 7 ) return
  39    40 mp1 = m + 1
  40       do 50 i = mp1,n,7
  41         dy(i) = dx(i)
  42         dy(i + 1) = dx(i + 1)
  43         dy(i + 2) = dx(i + 2)
  44         dy(i + 3) = dx(i + 3)
  45         dy(i + 4) = dx(i + 4)
  46         dy(i + 5) = dx(i + 5)
  47         dy(i + 6) = dx(i + 6)
  48    50 continue
  49       return
  50       end