C ++很慢 [英] C++ is slow

问题描述

我有以下两个程序：


PROG I

void main（）

{

int * v = new int [NUM];

for（int i = 0; i< NUM; ++ i）

v [i] = i ;

}


PROG II

class rvector

{

私人：

int * vals;

size_t vsize;


public：

显式rvector （size_t vSize）{vals = new int [vsize]; }

~rvector（）{delete [] vals; }


int& operator []（size_t idx）{return vals [idx]; }

};


void main（）

{

rvector v（NUM）;

for（i = 0; i< NUM; ++ i）

v [i] = i;

}


我省略了一些非关联线，例如，定义NUM并包括标题

文件。


我编译并运行这些程序使用VC ++ 6.0。第二个程序

所需的时间约为第一个的6倍。发生了什么

在程序II中花了那么多时间？


-charles

I have the following two programs:

PROG I
void main()
{
int *v = new int[NUM];
for (int i = 0; i < NUM; ++i)
v[i] = i;
}

PROG II
class rvector
{
private:
int* vals;
size_t vsize;

public:
explicit rvector( size_t vSize ) { vals = new int[vsize]; }
~rvector() { delete [] vals; }

int& operator[] (size_t idx ) { return vals[idx]; }
};

void main()
{
rvector v(NUM);
for (i = 0; i < NUM; ++i)
v[i] = i;
}

I left out some non-germane lines, eg, defining NUM and including header
files.

I compiled and ran these programs using VC++ 6.0. The second program
required approx 6 times as much time to run as the first. What is happening
in program II that takes so much time?

-charles

推荐答案

" Charles Herman" < CH ***** @ no.spam>在消息中写道

news：PO62c.120645

"Charles Herman" <ch*****@no.spam> wrote in message
news:PO62c.120645

Xp.533671@attbi_s54 ...

Xp.533671@attbi_s54...

我有以下两个程序：

PROG I
void main（）


int main（）


如果使用任何东西除了''int''返回类型

for main，你有* no *保证你的程序

的行为。

{
int * v = new int [NUM];
for（int i = 0; i< NUM; ++ i）
v [i] = i;


你有内存泄漏。你需要释放你分配的内存

。

}

PROG II
class rvector
{
private：
int * vals;
size_t vsize;

public：
显式rvector（size_t vSize）{vals = new int [vsize]; }
~rvector（）{delete [] vals; }

int& operator []（size_t idx）{return vals [idx]; }
};

void main（）


再次。

{
rvector v（ NUM）;
for（i = 0; i< NUM; ++ i）
v [i] = i;
}

我遗漏了一些非绅士行，例如，定义NUM并包括头文件。


如果可能的话，你应该总是努力发布*可编辑的*代码。然后我们不必猜测其余部分，这通常是说明问题的原因。
我使用VC ++ 6.0编译并运行这些程序。第二个程序需要大约6倍的运行时间。什么是
在程序II中发生需要花费这么多时间？

I have the following two programs:

PROG I
void main()
int main()

If you use anything else besides ''int'' return type
for main, you have *no* guarantees about the behavior of
your program.
{
int *v = new int[NUM];
for (int i = 0; i < NUM; ++i)
v[i] = i;
You have a memory leak. You need to free the memory
you allocate.
}

PROG II
class rvector
{
private:
int* vals;
size_t vsize;

public:
explicit rvector( size_t vSize ) { vals = new int[vsize]; }
~rvector() { delete [] vals; }

int& operator[] (size_t idx ) { return vals[idx]; }
};

void main()
And again.
{
rvector v(NUM);
for (i = 0; i < NUM; ++i)
v[i] = i;
}

I left out some non-germane lines, eg, defining NUM and including header
files.
You should always strive to post *compilable* code if at all
possible. Then we needn''t guess at the rest, which is often
the cause of a stated problem.

I compiled and ran these programs using VC++ 6.0. The second program
required approx 6 times as much time to run as the first. What is happening in program II that takes so much time?

C ++语言是一组规范，一个抽象。

我没有'速度'，慢或快。显然你发现C ++的特定的实现*（VC ++ 6.0）太慢。


推荐的行动：


阅读您的文档以确保您正确使用该产品，

并找到它的各种模式操作。


如果VC ++被认为是不可接受的，请使用别的东西。


-Mike

The C++ language is a set of specifications, an abstraction.
I has no ''speed'', slow or fast. Apparently you find a particular
*implementation* of C++, (VC++6.0) "too slow".

Recommended actions:

Read your documentation to ensure you''re using the product correctly,
and find it''s various ''modes'' of operation.

If VC++ is deemed unacceptable, use something else.

-Mike

" Mike Wahler" ; < MK ****** @ mkwahler.net>在消息中写道

新闻：OT ****************** @ newsread2.news.pas.earth link.net ...

"Mike Wahler" <mk******@mkwahler.net> wrote in message
news:OT******************@newsread2.news.pas.earth link.net...

查尔斯赫尔曼 < CH ***** @ no.spam>在消息中写道
新闻：PO62c.120645

"Charles Herman" <ch*****@no.spam> wrote in message
news:PO62c.120645

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