saxpy.c

来自「SuperLU 2.2版本。对大型、稀疏、非对称的线性系统的直接求解」· C语言 代码 · 共 95 行

/*  -- 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 saxpy_(integer *n, real *sa, real *sx, integer *incx, 
	real *sy, integer *incy)
{


    /* System generated locals */
    integer i__1;

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


/*     constant times a vector plus a vector.   
       uses unrolled loop for increments equal to one.   
       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 (*sa == 0.f) {
	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) {
	SY(iy) += *sa * SX(ix);
	ix += *incx;
	iy += *incy;
/* L10: */
    }
    return 0;

/*        code for both increments equal to 1   


          clean-up loop */

L20:
    m = *n % 4;
    if (m == 0) {
	goto L40;
    }
    i__1 = m;
    for (i = 1; i <= m; ++i) {
	SY(i) += *sa * SX(i);
/* L30: */
    }
    if (*n < 4) {
	return 0;
    }
L40:
    mp1 = m + 1;
    i__1 = *n;
    for (i = mp1; i <= *n; i += 4) {
	SY(i) += *sa * SX(i);
	SY(i + 1) += *sa * SX(i + 1);
	SY(i + 2) += *sa * SX(i + 2);
	SY(i + 3) += *sa * SX(i + 3);
/* L50: */
    }
    return 0;
} /* saxpy_ */