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Annotation of researchv10no/cmd/view2d/num/sswap.f, revision 1.1.1.1

1.1       root        1:       subroutine sswap (n,sx,incx,sy,incy)
                      2: c
                      3: c     interchanges two vectors.
                      4: c     uses unrolled loops for increments equal to 1.
                      5: c     jack dongarra, linpack, 3/11/78.
                      6: c
                      7:       real sx(1),sy(1),stemp
                      8:       integer i,incx,incy,ix,iy,m,mp1,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:         stemp = sx(ix)
                     22:         sx(ix) = sy(iy)
                     23:         sy(iy) = stemp
                     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: c
                     32: c       clean-up loop
                     33: c
                     34:    20 m = mod(n,3)
                     35:       if( m .eq. 0 ) go to 40
                     36:       do 30 i = 1,m
                     37:         stemp = sx(i)
                     38:         sx(i) = sy(i)
                     39:         sy(i) = stemp
                     40:    30 continue
                     41:       if( n .lt. 3 ) return
                     42:    40 mp1 = m + 1
                     43:       do 50 i = mp1,n,3
                     44:         stemp = sx(i)
                     45:         sx(i) = sy(i)
                     46:         sy(i) = stemp
                     47:         stemp = sx(i + 1)
                     48:         sx(i + 1) = sy(i + 1)
                     49:         sy(i + 1) = stemp
                     50:         stemp = sx(i + 2)
                     51:         sx(i + 2) = sy(i + 2)
                     52:         sy(i + 2) = stemp
                     53:    50 continue
                     54:       return
                     55:       end

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