dswap.c (ulmBLAS/src/level1/dswap.c)

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#include <ulmblas.h>

void

ULMBLAS(dswap)(const int n,

               double    *x,

               const int incX,

               double    *y,

               const int incY)

{

//

//  Local scalars

//

    int    i, m;

    double tmp;

//

//  Quick return if possible

//

    if (n==0) {

        return;

    }

    if (incX==1 && incY==1) {

//

//      Code for both increments equal to 1

//

        m = n % 3;

        if (m!=0) {

            for (i=0; i<m; ++i) {

                tmp  =  x[i];

                x[i] = y[i];

                y[i] = tmp;

            }

            if (n<3) {

                return;

            }

        }

        for (i=m; i<n; i+=3) {

            tmp  =  x[i];

            x[i] = y[i];

            y[i] = tmp;

            tmp    =  x[i+1];

            x[i+1] = y[i+1];

            y[i+1] = tmp;

            tmp    =  x[i+2];

            x[i+2] = y[i+2];

            y[i+2] = tmp;

        }

    } else {

//

//      Code for unequal increments or equal increments not equal to 1

//

        if (incX<0) {

            x -= incX*(n-1);

        }

        if (incY<0) {

            y -= incY*(n-1);

        }

        for (i=0; i<n; ++i, x+=incX, y+=incY) {

            tmp = *x;

            *x  = *y;

            *y  = tmp;

        }

    }

}

void

F77BLAS(dswap)(const int *_n,

               double    *x,

               const int *_incX,

               double    *y,

               const int *_incY)

{

//

//  Dereference scalar parameters

//

    int n    = *_n;

    int incX = *_incX;

    int incY = *_incY;

    ULMBLAS(dswap)(n, x, incX, y, incY);

}