sswap.c

来自「NIST Handwriting OCR Testbed」· C语言 代码 · 共 110 行

/*
* ======================================================================
* NIST Guide to Available Math Software.
* Fullsource for module SSWAP.C from package CBLAS.
* Retrieved from NETLIB on Tue Mar 14 10:50:48 2000.
* ======================================================================
*/

/*  -- translated by f2c (version 19940927).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include <f2c.h>

/* Subroutine */ int sswap_(integer *n, real *sx, integer *incx, real *sy, 
	integer *incy)
{


    /* System generated locals */
    integer i__1;

    /* Local variables */
    static integer i, m;
    static real stemp;
    static integer ix, iy, mp1;


/*     interchanges two vectors.   
       uses unrolled loops for increments equal to 1.   
       jack dongarra, linpack, 3/11/78.   
       modified 12/3/93, array(1) declarations changed to array(*)   


    
   Parameter adjustments   
       Function Body */
#define SY(I) sy[(I)-1]
#define SX(I) sx[(I)-1]


    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 <= *n; ++i) {
	stemp = SX(ix);
	SX(ix) = SY(iy);
	SY(iy) = stemp;
	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 <= m; ++i) {
	stemp = SX(i);
	SX(i) = SY(i);
	SY(i) = stemp;
/* L30: */
    }
    if (*n < 3) {
	return 0;
    }
L40:
    mp1 = m + 1;
    i__1 = *n;
    for (i = mp1; i <= *n; i += 3) {
	stemp = SX(i);
	SX(i) = SY(i);
	SY(i) = stemp;
	stemp = SX(i + 1);
	SX(i + 1) = SY(i + 1);
	SY(i + 1) = stemp;
	stemp = SX(i + 2);
	SX(i + 2) = SY(i + 2);
	SY(i + 2) = stemp;
/* L50: */
    }
    return 0;
} /* sswap_ */