sswap.c

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/* interchanges two vectors
   uses unrolled loops for increments equal to 1.
   Ver.1.0, May,26,1988.                         */
 
#include "arith.h"
 
sswap(n,sx,isx,jsx,incx,sy,isy,jsy,incy)
int n,isx,jsx,incx,isy,jsy,incy;
MATRIX sx,sy;
{
    REAL stemp;
    int i,ix,iy,m;
 
    if(n <= 0)
        return;
 
    /* code for both increments equal to 1 */
 
    /* clean-up loop */
 
    m=n%3;
    if(m != 0){
        for(i=0; i<m; i++){
            stemp=sx[isx+i][jsx];
            sx[isx+i][jsx]=sy[isy+i][jsy];
            sy[isy+i][jsy]=stemp;
        }
        if(n < 3)
            return;
    }
 
    for(i=m; i<n; i += 3){
            stemp=sx[isx+i][jsx];
            sx[isx+i][jsx]=sy[isy+i][jsy];
            sy[isy+i][jsy]=stemp;
            stemp=sx[isx+i+1][jsx];
            sx[isx+i+1][jsx]=sy[isy+i+1][jsy];
            sy[isy+i+1][jsy]=stemp;
            stemp=sx[isx+i+2][jsx];
            sx[isx+i+2][jsx]=sy[isy+i+2][jsy];
            sy[isy+i+2][jsy]=stemp;
        }
}