sscal.c

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/* scales a vector by a constant.
   uses unrolled loops for increment equal to 1
   Ver.1.0, May,26,1988.                       */

#include "arith.h"

sscal(n,sa,sx,isx,jsx,incx)
int n,isx,jsx,incx;
REAL sa;
MATRIX sx;
{
    int i,m,nincx;

    if(n <= 0)
        return;

    if(incx != 1){

        /* code for increment not equal to 1 */

        nincx= n*incx;
        for(i=0; i<nincx; i += incx)
            sx[isx+i][jsx]= sa*sx[isx+i][jsx];
    }

    else{

        /* code for increment equal to 1 */

        /* clean-up loop */

        m=n%5;
        if(m != 0){
            for(i=0; i<m; i++)
                sx[isx+i][jsx]= sa*sx[isx+i][jsx];
            if(n < 5)
                return;
        }

        for(i=m; i<n; i += 5){
            sx[isx+i][jsx] = sa*sx[isx+i][jsx];
            sx[isx+i+1][jsx] = sa*sx[isx+i+1][jsx];
            sx[isx+i+2][jsx] = sa*sx[isx+i+2][jsx];
            sx[isx+i+3][jsx] = sa*sx[isx+i+3][jsx];
            sx[isx+i+4][jsx] = sa*sx[isx+i+4][jsx];
        }
    }
}