C 如何改进功能?
我有一个程序,计算2到26的幂和结果数的根 程序的源代码包含在几个文件中,我使用makefile和C 如何改进功能?,c,optimization,gprof,C,Optimization,Gprof,我有一个程序,计算2到26的幂和结果数的根 程序的源代码包含在几个文件中,我使用makefile和-pg标志编译它。我通过gprof./main运行它,结果得到: Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls s/call s/call name 51.95
-pg
标志编译它。我通过gprof./main运行它,结果得到:
Each sample counts as 0.01 seconds.
% cumulative self self total
time seconds seconds calls s/call s/call name
51.95 1.73 1.73 52 0.03 0.03 very_smart_add
32.73 2.82 1.09 67108863 0.00 0.00 give_me_sum
11.71 3.21 0.39 13 0.03 0.16 the_middle_of
3.60 3.33 0.12 26 0.00 0.05 give_me_product
0.00 3.33 0.00 13 0.00 0.13 the_middle_of2
0.00 3.33 0.00 1 0.00 1.21 give_me_power
0.00 3.33 0.00 1 0.00 2.12 square_root
我想提高最耗时的功能,但我不知道如何做到这一点。在这种情况下可以做什么
文件:
第1.c部分
:
long long give_me_product(long long a, long long b);
long long give_me_power(long long a, long long b)
{
long long ret = 1;
while (b--)
{
ret = give_me_product(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b);
long long give_me_product(long long a, long long b)
{
long long ret = 0;
while (b--)
{
ret = give_me_sum(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b)
{
long long ret = 0;
while (a--)
{
ret++;
}
return ret + b;
while (b--)
{
ret++;
}
return ret;
}
#define EPS 0.0000000001
#define STEP 1.0
/* This function adds two numbers. */
double very_smart_add(double a, double b)
{
while (b >= STEP)
{
a += STEP;
b -= STEP;
}
a += b;
return a;
}
double the_middle_of2(double a, double b)
{
double l = a, r = b;
double check, m;
while (1)
{
m = very_smart_add(l, r)/2;
check = very_smart_add(m, m);
if (check > very_smart_add(a, b) + EPS)
r = m;
else if (check < very_smart_add(a, b) - EPS)
l = m;
else
return m;
}
}
double the_middle_of(double a, double b)
{
double r = 0;
double s = a + b;
while (r + r < s)
{
r += 1.0;
}
return the_middle_of2(r - 1.0, s - (r - 1.0));
}
double square_root(double x)
{
double l = 0, r = x;
double check, m;
while (1)
{
m = the_middle_of(l, r);
check = m * m;
if (check > x + EPS)
r = m;
else if (check < x - EPS)
l = m;
else
return m;
}
}
第2.c部分
:
long long give_me_product(long long a, long long b);
long long give_me_power(long long a, long long b)
{
long long ret = 1;
while (b--)
{
ret = give_me_product(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b);
long long give_me_product(long long a, long long b)
{
long long ret = 0;
while (b--)
{
ret = give_me_sum(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b)
{
long long ret = 0;
while (a--)
{
ret++;
}
return ret + b;
while (b--)
{
ret++;
}
return ret;
}
#define EPS 0.0000000001
#define STEP 1.0
/* This function adds two numbers. */
double very_smart_add(double a, double b)
{
while (b >= STEP)
{
a += STEP;
b -= STEP;
}
a += b;
return a;
}
double the_middle_of2(double a, double b)
{
double l = a, r = b;
double check, m;
while (1)
{
m = very_smart_add(l, r)/2;
check = very_smart_add(m, m);
if (check > very_smart_add(a, b) + EPS)
r = m;
else if (check < very_smart_add(a, b) - EPS)
l = m;
else
return m;
}
}
double the_middle_of(double a, double b)
{
double r = 0;
double s = a + b;
while (r + r < s)
{
r += 1.0;
}
return the_middle_of2(r - 1.0, s - (r - 1.0));
}
double square_root(double x)
{
double l = 0, r = x;
double check, m;
while (1)
{
m = the_middle_of(l, r);
check = m * m;
if (check > x + EPS)
r = m;
else if (check < x - EPS)
l = m;
else
return m;
}
}
第3.c部分
:
long long give_me_product(long long a, long long b);
long long give_me_power(long long a, long long b)
{
long long ret = 1;
while (b--)
{
ret = give_me_product(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b);
long long give_me_product(long long a, long long b)
{
long long ret = 0;
while (b--)
{
ret = give_me_sum(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b)
{
long long ret = 0;
while (a--)
{
ret++;
}
return ret + b;
while (b--)
{
ret++;
}
return ret;
}
#define EPS 0.0000000001
#define STEP 1.0
/* This function adds two numbers. */
double very_smart_add(double a, double b)
{
while (b >= STEP)
{
a += STEP;
b -= STEP;
}
a += b;
return a;
}
double the_middle_of2(double a, double b)
{
double l = a, r = b;
double check, m;
while (1)
{
m = very_smart_add(l, r)/2;
check = very_smart_add(m, m);
if (check > very_smart_add(a, b) + EPS)
r = m;
else if (check < very_smart_add(a, b) - EPS)
l = m;
else
return m;
}
}
double the_middle_of(double a, double b)
{
double r = 0;
double s = a + b;
while (r + r < s)
{
r += 1.0;
}
return the_middle_of2(r - 1.0, s - (r - 1.0));
}
double square_root(double x)
{
double l = 0, r = x;
double check, m;
while (1)
{
m = the_middle_of(l, r);
check = m * m;
if (check > x + EPS)
r = m;
else if (check < x - EPS)
l = m;
else
return m;
}
}
sqrt.c
:
long long give_me_product(long long a, long long b);
long long give_me_power(long long a, long long b)
{
long long ret = 1;
while (b--)
{
ret = give_me_product(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b);
long long give_me_product(long long a, long long b)
{
long long ret = 0;
while (b--)
{
ret = give_me_sum(a, ret);
}
return ret;
}
long long give_me_sum(long long a, long long b)
{
long long ret = 0;
while (a--)
{
ret++;
}
return ret + b;
while (b--)
{
ret++;
}
return ret;
}
#define EPS 0.0000000001
#define STEP 1.0
/* This function adds two numbers. */
double very_smart_add(double a, double b)
{
while (b >= STEP)
{
a += STEP;
b -= STEP;
}
a += b;
return a;
}
double the_middle_of2(double a, double b)
{
double l = a, r = b;
double check, m;
while (1)
{
m = very_smart_add(l, r)/2;
check = very_smart_add(m, m);
if (check > very_smart_add(a, b) + EPS)
r = m;
else if (check < very_smart_add(a, b) - EPS)
l = m;
else
return m;
}
}
double the_middle_of(double a, double b)
{
double r = 0;
double s = a + b;
while (r + r < s)
{
r += 1.0;
}
return the_middle_of2(r - 1.0, s - (r - 1.0));
}
double square_root(double x)
{
double l = 0, r = x;
double check, m;
while (1)
{
m = the_middle_of(l, r);
check = m * m;
if (check > x + EPS)
r = m;
else if (check < x - EPS)
l = m;
else
return m;
}
}
#定义每股收益0.0000000001
#定义步骤1.0
/*此函数用于添加两个数字*/
双倍非常智能添加(双倍a,双倍b)
{
while(b>=步)
{
a+=阶跃;
b-=阶跃;
}
a+=b;
返回a;
}
双倍于2的中间(双倍a,双倍b)
{
双l=a,r=b;
重复检查,m;
而(1)
{
m=非常聪明的加(l,r)/2;
检查=非常智能添加(m,m);
如果(检查>非常聪明添加(a,b)+EPS)
r=m;
否则如果(检查x+EPS)
r=m;
否则如果(检查
看起来像是一个家庭作业,但我将提供一个简化加法的方法-消除不必要的while循环,并可能检测溢出
将此移动到社区wiki
long long give_me_sum(long long a, long long b) {
#if NEED_TO_PREVENT_UNDEFINED_BEHAVIOR
if (a >= 0) {
if (b > LLONG_MAX - a) return LLONG_MAX;
} else {
if (b < LLONG_MIN - a) return LLONG_MIN;
}
#endif
return a + b;
}
long long give_me_sum(long long a,long long b){
#如果需要防止未定义的行为
如果(a>=0){
如果(b>LLONG_MAX-a)返回LLONG_MAX;
}否则{
如果(b
你给我力量
功能为O(n)。您可以将其优化为O(logn)
TL/DR,但是sqrt(2^26)=2您的个人资料说very_-smart\u-add
是时间汇,所以我会从这里开始,也许会解释它的聪明之处。此外,very_-smart\u-add()
不是很聪明。@krzyhub这是这个案例的改进:return 8192代码>.2^13=8192,而2