请教：优化这个函数里的代码，高手请进~~

[genieyyt]

注重效率，在汇编层面上哪怕能减少一行，也给分~~
typedef struct { /* Line Information */
long x1; /* start point */
long y1;
long x2; /* end point */
long y2;
double ki; /* slope */
double y0; /* y clip */
long sx; /* on sort line */
long rx;
long f; /* line course flag */
/* 0 : Even/Odd rule */
/* 1 : Non-Zero winding rule */
} LineInfo ;
/********************************************************************

Class : CALC
Method : calculateCrossing
Arg1 : 1st line information pointer
Arg2 : 2nd line information pointer
Arg3 : Y Coordinate on Crossing
Return : true:crossing/false:not crossing

********************************************************************/

bool
CALC::calculateCrossing(LineInfo *line1,LineInfo *line2,long *cross_y)
{
long y;
double f_ki,f_y,tmp_y;
int flag = 0;
bool ret;

ret = false; /* not crossing */
if (line1->y1 == line2->y1)
if (line1->x1 == line2->x1) return(ret);
if (line1->y1 == line2->y2)
if (line1->x1 == line2->x2) return(ret);
if (line1->y2 == line2->y1)
if (line1->x2 == line2->x1) return(ret);
if (line1->y2 == line2->y2)
if (line1->x2 == line2->x2) return(ret);

if((line1->y1 == line1->y2) || (line2->y1 == line2->y2)) {
/* y1 == y2 then horizontal */
return(ret);
}

f_ki = line2->ki - line1->ki;
if(f_ki != 0) { /* == 0 then parallel */
if(line1->ki == 0) {
f_y = line1->x1 * line2->ki + line2->y0;
} else if(line2->ki == 0) {
f_y = line2->x1 * line1->ki + line1->y0;
} else {
tmp_y = (line2->ki * line1->y0) - (line1->ki * line2->y0);
f_y = tmp_y / f_ki;
if ((f_y * f_ki) != tmp_y)
flag = 1; /* float devision diff */
}
y = (long)f_y; /* y-axis down */
if ((double)y != f_y) y++; /* y-axis up */
else if (flag) y++;

if(((line1->y1 < y) && (y < line1->y2))
&& ((line2->y1 < y) && (y < line2->y2))) {
/* in y-axis */

ret = true; /* crossing */
*cross_y = y ;
}
}

return(ret);
}

[genieyyt]

补充一下环境
HOSTTYPE=powermac
VENDOR=apple
MACHTYPE=powerpc
编译器优化选项 -O2

[iambic]

拿中文解释下你这是算啥的。

[yshuise]

第一：初略看了一下，if else 需要调整
第二：加inline关键字

[herman~~]

学习

[nullah]

up

[genieyyt]

[Quote=引用 11 楼 iambic 的回复:]
拿中文解释下你这是算啥的。
[/Quote]
在2维坐标平面
给出2条线（起点终点斜率），
判断相交不相交，相交算2线的交点y值

[zh_zhen]

1.多用加减和位运算，少用乘除；
2.多用整数运算，少用浮点运算；
3.浮点运算不当用==、！等运算符；
4.代码长短和运行效率没有必然关系。

[Allen_zhang]

你这个是算两条直线有没有交点吧？

不过这个可能有问题
因为这样算会有数学误差的

[genieyyt]

代码没对整齐，在贴遍代码
typedef struct { /* Line Information */
long x1; /* start point */
long y1;
long x2; /* end point */
long y2;
double ki; /* slope */
double y0; /* y clip */
long sx; /* on sort line */
long rx;
long f; /* line course flag */
/* 0 : Even/Odd rule */
/* 1 : Non-Zero winding rule */
} LineInfo ;
/********************************************************************

Class : CALC
Method : calculateCrossing
Arg1 : 1st line information pointer
Arg2 : 2nd line information pointer
Arg3 : Y Coordinate on Crossing
Return : true:crossing/false:not crossing

********************************************************************/

bool
CALC::calculateCrossing(LineInfo *line1,LineInfo *line2,long *cross_y)
{
long y;
double f_ki,f_y,tmp_y;
int flag = 0;
bool ret;

ret = false; /* not crossing */
if (line1->y1 == line2->y1)
if (line1->x1 == line2->x1) return(ret);
if (line1->y1 == line2->y2)
if (line1->x1 == line2->x2) return(ret);
if (line1->y2 == line2->y1)
if (line1->x2 == line2->x1) return(ret);
if (line1->y2 == line2->y2)
if (line1->x2 == line2->x2) return(ret);

if((line1->y1 == line1->y2) || (line2->y1 == line2->y2)) {
/* y1 == y2 then horizontal */
return(ret);
}

f_ki = line2->ki - line1->ki;
if(f_ki != 0) { /* == 0 then parallel */
if(line1->ki == 0) {
f_y = line1->x1 * line2->ki + line2->y0;
} else if(line2->ki == 0) {
f_y = line2->x1 * line1->ki + line1->y0;
} else {
tmp_y = (line2->ki * line1->y0) - (line1->ki * line2->y0);
f_y = tmp_y / f_ki;
if ((f_y * f_ki) != tmp_y)
flag = 1; /* float devision diff */
}
y = (long)f_y; /* y-axis down */
if ((double)y != f_y) y++; /* y-axis up */
else if (flag) y++;

if(((line1->y1 < y) && (y < line1->y2))
&& ((line2->y1 < y) && (y < line2->y2))) {
/* in y-axis */

ret = true; /* crossing */
*cross_y = y ;
}
}

return(ret);
}

[taodm]

换一台最强劲的计算机，程序性能立即提高30%。

[tanmeining]

typedef struct {                                /* Line Information                    */ 
        long    x1;                            /* start point                          */ 
        long    y1; 
        long    x2;                            /* end point                            */ 
        long    y2; 
        double  ki;                            /* slope                                */ 
        double  y0;                            /* y clip                              */ 
        long    sx;                            /* on sort line                        */ 
        long    rx; 
        long    f;                              /* line course flag                    */ 
                                                /* 0 : Even/Odd rule                    */ 
                                                /* 1 : Non-Zero winding rule            */ 
} LineInfo ; 
/******************************************************************** 

        Class  : CALC 
        Method  : calculateCrossing 
        Arg1    : 1st line information pointer 
        Arg2    : 2nd line information pointer 
        Arg3    : Y Coordinate on Crossing 
        Return  : true:crossing/false:not crossing 

********************************************************************/ 

bool 
CALC::calculateCrossing(LineInfo *line1,LineInfo *line2,long *cross_y) 
{ 
    long        y; 
    double      f_ki,f_y,tmp_y; 
    int    flag = 0; 
    bool        ret = false; //modefied
    
    //ret = false;                                                                /* not crossing                */     
    if((line1->y1 == line1->y2) || (line2->y1 == line2->y2)) 
    { 
                                                                                /* y1 == y2 then horizontal    */ 
        return(ret); 
    } 
     
    if (line1->y1 == line2->y1)
    { 
        if (line1->x1 == line2->x1)
           return(ret); 
    }else
    if (line1->y1 == line2->y2)
    { 
        if (line1->x1 == line2->x2)
           return(ret); 
    }else
    if (line1->y2 == line2->y1)
    { 
        if (line1->x2 == line2->x1)
           return(ret); 
    }else
    if (line1->y2 == line2->y2) 
    {
        if (line1->x2 == line2->x2)
           return(ret); 
    }
    
    f_ki = line2->ki - line1->ki; 
    if(f_ki) 
    {                                                            /* == 0 then parallel          */ 
        if(!line1->ki)
        { 
                f_y = line1->x1 * line2->ki + line2->y0;
        }else 
        if(!line2->ki)
        { 
                f_y = line2->x1 * line1->ki + line1->y0;
        }else
        { 
                tmp_y = (line2->ki * line1->y0) - (line1->ki * line2->y0); 
                f_y = tmp_y / f_ki;
                if ((f_y * f_ki) != tmp_y) 
                        flag = 1;                                              /* float devision diff          */ 
        } 
        y = (long)f_y;                                                          /* y-axis down                  */ 
        if ((double)y != f_y)  
        {
            ++y;                                            /* y-axis up                    */ 
        }else
        if (flag)
        {
            ++y; 
        }

        if(((line1->y1 < y) && (y < line1->y2)) 
                        && ((line2->y1 < y) && (y < line2->y2)))
        { 
                                                                                /* in y-axis                    */ 
    
                ret = true;                                                    /* crossing                    */ 
                *cross_y = y;
        } 
    } 
    
    return(ret);
}    

[hemiya]

/*
    if (line1->y1 == line2->y1) 
        if (line1->x1 == line2->x1) return(ret); 
    if (line1->y1 == line2->y2) 
        if (line1->x1 == line2->x2) return(ret); 
    if (line1->y2 == line2->y1) 
        if (line1->x2 == line2->x1) return(ret); 
    if (line1->y2 == line2->y2) 
        if (line1->x2 == line2->x2) return(ret); 
    
    if((line1->y1 == line1->y2) || (line2->y1 == line2->y2)) { 
                                                                                /* y1 == y2 then horizontal    */ 
        return(ret); 
    }
*/
    if (((line1->y1 == line2->y1) && (line1->x1 == line2->x1)) || 
        ((line1->y1 == line2->y2) && (line1->x1 == line2->x2)) ||
        ((line1->y2 == line2->y1) && (line1->x2 == line2->x1)) ||
        ((line1->y2 == line2->y2) && (line1->x2 == line2->x2)) ||
        ((line1->y1 == line1->y2) || (line2->y1 == line2->y2)))
        return (ret);

[tanmeining]

其他的具体算法,不懂你那是做什么的,所以不敢动。
同时觉得仅仅缩减10+行左右的汇编代码并不能将效率提高多少,建议搂主还是在循环中着手试下...
比如for循环i++之类的改成++i这样子,还有就是算法方面再考虑考虑是否有更精简的.

[tanmeining]

[Quote=引用 4 楼 hemiya 的回复:]
C/C++ code
/*
if (line1->y1 == line2->y1)
if (line1->x1 == line2->x1) return(ret);
if (line1->y1 == line2->y2)
if (line1->x1 == line2->x2) return(ret);
if (line1->y2 == line2->y1)
if (line1->x2 == line2->x1) return(ret);
if (line1->y2 == line2->y2)
if (line1->x2 == line2->x2) return(ret);

if((line1->y1 == line1->y2) || (…
[/Quote]

顶,我还看成了if (line1->y1 == line2->y1) 则line1->x1 = line2->x1,郁闷,太粗心了...

[xiaoyisnail]

if/else块把最可能的情况写在前面，可以减少很多判断的次数

[hemiya]

建议楼主行注释不要写c风格的
/*....*/
要写c++风格的
//....
看我4楼的回复就明白了.

[waizqfor]

[Quote=引用 4 楼 hemiya 的回复:]
C/C++ code
/*
if (line1->y1 == line2->y1)
if (line1->x1 == line2->x1) return(ret);
if (line1->y1 == line2->y2)
if (line1->x1 == line2->x2) return(ret);
if (line1->y2 == line2->y1)
if (line1->x2 == line2->x1) return(ret);
if (line1->y2 == line2->y2)
if (line1->x2 == line2->x2) return(ret);

if((line1->y1 == line1->y2) || (…
[/Quote]
简单的优化也就像这样了 还有就是同类变量最好写在一起 减少不必要的代码行数