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- subroutine sswapf (n,sx,incx,sy,incy)
- c
- c interchanges two vectors.
- c uses unrolled loops for increments equal to 1.
- c jack dongarra, linpack, 3/11/78.
- c modified 12/3/93, array(1) declarations changed to array(*)
- c
- real sx(*),sy(*),stemp
- integer i,incx,incy,ix,iy,m,mp1,n
- c
- if(n.le.0)return
- if(incx.eq.1.and.incy.eq.1)go to 20
- c
- c code for unequal increments or equal increments not equal
- c to 1
- c
- ix = 1
- iy = 1
- if(incx.lt.0)ix = (-n+1)*incx + 1
- if(incy.lt.0)iy = (-n+1)*incy + 1
- do 10 i = 1,n
- stemp = sx(ix)
- sx(ix) = sy(iy)
- sy(iy) = stemp
- ix = ix + incx
- iy = iy + incy
- 10 continue
- return
- c
- c code for both increments equal to 1
- c
- c
- c clean-up loop
- c
- 20 m = mod(n,3)
- if( m .eq. 0 ) go to 40
- do 30 i = 1,m
- stemp = sx(i)
- sx(i) = sy(i)
- sy(i) = stemp
- 30 continue
- if( n .lt. 3 ) return
- 40 mp1 = m + 1
- do 50 i = mp1,n,3
- stemp = sx(i)
- sx(i) = sy(i)
- sy(i) = stemp
- stemp = sx(i + 1)
- sx(i + 1) = sy(i + 1)
- sy(i + 1) = stemp
- stemp = sx(i + 2)
- sx(i + 2) = sy(i + 2)
- sy(i + 2) = stemp
- 50 continue
- return
- end
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