#include "f2c.h"

/*#include "blaswrap.h"*/

/* Subroutine */ int dswap_(integer *n, doublereal *dx, integer *incx, 

	doublereal *dy, integer *incy)

{

    /* System generated locals */

    integer i__1;

    /* Local variables */

    integer i__, m, ix, iy, mp1;

    doublereal dtemp;

/*     .. Scalar Arguments .. */

/*     .. */

/*     .. Array Arguments .. */

/*     .. */

/*  Purpose */

/*  ======= */

/*     interchanges two vectors. */

/*     uses unrolled loops for increments equal one. */

/*     jack dongarra, linpack, 3/11/78. */

/*     modified 12/3/93, array(1) declarations changed to array(*) */

/*     .. Local Scalars .. */

/*     .. */

/*     .. Intrinsic Functions .. */

/*     .. */

    /* Parameter adjustments */

    --dy;

    --dx;

    /* Function Body */

    if (*n <= 0) {

	return 0;

    }

    if (*incx == 1 && *incy == 1) {

	goto L20;

    }

/*       code for unequal increments or equal increments not equal */

/*         to 1 */

    ix = 1;

    iy = 1;

    if (*incx < 0) {

	ix = (-(*n) + 1) * *incx + 1;

    }

    if (*incy < 0) {

	iy = (-(*n) + 1) * *incy + 1;

    }

    i__1 = *n;

    for (i__ = 1; i__ <= i__1; ++i__) {

	dtemp = dx[ix];

	dx[ix] = dy[iy];

	dy[iy] = dtemp;

	ix += *incx;

	iy += *incy;

/* L10: */

    }

    return 0;

/*       code for both increments equal to 1 */

/*       clean-up loop */

L20:

    m = *n % 3;

    if (m == 0) {

	goto L40;

    }

    i__1 = m;

    for (i__ = 1; i__ <= i__1; ++i__) {

	dtemp = dx[i__];

	dx[i__] = dy[i__];

	dy[i__] = dtemp;

/* L30: */

    }

    if (*n < 3) {

	return 0;

    }

L40:

    mp1 = m + 1;

    i__1 = *n;

    for (i__ = mp1; i__ <= i__1; i__ += 3) {

	dtemp = dx[i__];

	dx[i__] = dy[i__];

	dy[i__] = dtemp;

	dtemp = dx[i__ + 1];

	dx[i__ + 1] = dy[i__ + 1];

	dy[i__ + 1] = dtemp;

	dtemp = dx[i__ + 2];

	dx[i__ + 2] = dy[i__ + 2];

	dy[i__ + 2] = dtemp;

/* L50: */

    }

    return 0;

} /* dswap_ */