share/lapack/blas/fortran/drot.f

   1       subroutine  drot (n,dx,incx,dy,incy,c,s)
   2 c
   3 c     applies a plane rotation.
   4 c     jack dongarra, linpack, 3/11/78.
   5 c     modified 12/3/93, array(1) declarations changed to array(*)
   6 c
   7       double precision dx(*),dy(*),dtemp,c,s
   8       integer i,incx,incy,ix,iy,n
   9 c
  10       if(n.le.0)return
  11       if(incx.eq.1.and.incy.eq.1)go to 20
  12 c
  13 c       code for unequal increments or equal increments not equal
  14 c         to 1
  15 c
  16       ix = 1
  17       iy = 1
  18       if(incx.lt.0)ix = (-n+1)*incx + 1
  19       if(incy.lt.0)iy = (-n+1)*incy + 1
  20       do 10 i = 1,n
  21         dtemp = c*dx(ix) + s*dy(iy)
  22         dy(iy) = c*dy(iy) - s*dx(ix)
  23         dx(ix) = dtemp
  24         ix = ix + incx
  25         iy = iy + incy
  26    10 continue
  27       return
  28 c
  29 c       code for both increments equal to 1
  30 c
  31    20 do 30 i = 1,n
  32         dtemp = c*dx(i) + s*dy(i)
  33         dy(i) = c*dy(i) - s*dx(i)
  34         dx(i) = dtemp
  35    30 continue
  36       return
  37       end