集合类性能似乎是SLOOOWWWWWW [英] collection class performance seems SLOOOWWWWWW

问题描述

我在这里有一小部分代码。当button1_Click时被称为b $ b的表现相当差（~0.5秒）。唯一的事情就是我

没有真正做任何事情！在C ++中，同样的事情需要~0秒才能执行!! b $ b执行!!列表< Pumpicle>比ArrayList更快，我在访问之前将List转换为数组。它似乎就像

拆开Pumpicle类的双打。任何想法??


PumpicleContainer pc = null;


private void Form1_Load（object sender，EventArgs e）

{

pc = new PumpicleContainer（）;


for（int i = 0; i< 10000; i ++）

{

pc.Add（new Pumpicle（））;

}


pc.ToArray（）;

}


公共课DaublePoint

{

公共双m_x;

public double m_y;

public double m_z;

};


public class Pumpicle

{

public DaublePoint m_pos;

public double m_mass;


public Pumpicle（）

{

m_pos = new DaublePoint（）;

}

};


类PumpicleContainer
{

public List< Pumpicle> m_pList = new List< Pumpicle>（）;


Pumpicle [] m_arr = null;


public void Add（Pumpicle p）

{

m_pList.Add（p）;

}


public void ToArray（）

{

m_arr = m_pList.ToArray（）;

}


public Pumpicle GetParticle（int i ）

{

返回m_arr [i];

}

}


private void button1_Click（object sender，EventArgs e）

{

pc.ToArray（）;


long start = System.DateTime.Now.Ticks;


int np = 0;

for（int idx = 0; idx< 20; idx ++）

{

np + = 22;

for（int i = -33; i< = 33; i ++）

{

for（int j = -33; j< = 33; j ++）

{

for（int l = 0; l< 5; l ++）

{

for（int ps = 0; ps< np; ps ++）

{

Pumpicle p = pc.GetParticle（ps）;


DaublePoint pt = pm _pos;

double x = pt.m_x;

double y = pt.m_y;

double z = pt.m_z;

}

}

}

}

}


long end = System.DateTime.Now.Ticks;


MessageBox.Show（" Finished =" +（（结束 - 开始）/ 1e7））;

}

解决方案

我注意到一对夫妇事情。


你通过那些嵌套的for循环进行了448900次迭代（而且我是

甚至不计算ps< np循环 - 谁知道这会增加什么呢。


你正在测量错误的时间。而不是

System.DateTime.Now.Ticks，在两个地方都使用System.DateTime.Now。然后

减去它们并到达TimeSpan，然后在

TimeSpan对象上调用elapsedMillis（）。你现在测量它的方式，如果碰巧越过第二个边界，你可能会遇到非常不一致的执行时间。


DateTime then = System .DateTime.Now;

//你的循环在这里。

DateTime now = System.DateTime.Now;

TimeSpan ts = now - then ;

Console.WriteLine（ts.TotalMilliseconds）;


Jeremiah

ia ******* @ bmtcordah.com 写道：

我在这里有一小部分代码。当button1_Click时被称为性能相当差（~0.5秒）。唯一的事就是我没有真正做任何事情！在C ++中，同样的事情需要大约0秒才能执行!!列表< Pumpicle>比ArrayList快，我在访问之前将List转换为数组。它似乎就像是取消了Pumpicle类中的双打。任何想法??

PumpicleContainer pc = null;

private void Form1_Load（object sender，EventArgs e）
{
pc = new PumpicleContainer（） ;

for（int i = 0; i< 10000; i ++）
{
pc.Add（new Pumpicle（））;
}
pc.ToArray（）;
}
公共课DaublePoint
{公共双m_x;
公共双m_y;
public double m_z;
};

公共类Pumpicle
公共DaublePoint m_pos;
公共双m_mass;

public Pumpicle（）
{
m_pos = new DaublePoint（）;
}
};

类PumpicleContainer
{
Pumpicle [] m_arr = null;

public void Add（Pumpicle p）
{
m_pList .Add（p）;
}

public void ToArray（）
{
m_arr = m_pList.ToArray（）;
}

公共Pumpicle GetParticle（int i）
{
返回m_arr [i];
}
}
私有void button1_Click（对象发送者） ，EventArgs e）
{
pc.ToArray（）;

long start = System.DateTime.Now.Ticks;

int np = 0 ;
for（int idx = 0; idx< 20; idx ++）
{
np + = 22;
for（int i = -33; i< = 33 ; i ++）
{
for（int j = -33; j< = 33; j ++）
{
for（int l = 0; l< 5; l ++ ）
{
for（int ps = 0; ps< np; ps ++）
{/> Pumpicle p = pc.GetParticle（ps）;
DaublePoint pt = p.m_pos;
double x = pt.m_x;
double y = pt.m_y;
double z = pt.m_z;
}
}
}
}

long end = System.DateTime.Now.Ticks;

MessageBox。显示（" Finished =" +（（结束 - 开始）/ 1e7））;
}

ia ******* @ bmtcordah.com 写道：

唯一的事情是我不是在做任何事情！在C ++中，同样的事情需要大约0秒才能执行!!
int np = 0;
for（int idx = 0; idx< 20; idx ++）
{
np + = 22;
for（int i = -33; i< = 33; i ++）
{
for（int j = -33; j< = 33; j ++）
{
for（int l = 0; l< 5; l ++）
{
for（int ps = 0; ps< np; ps ++）
{/> Pumpicle p = pc.GetParticle（ps） ;

DaublePoint pt = p.m_pos;
double x = pt.m_x;
double y = pt.m_y;
double z = pt.m_z; < $
}
}


对这样的比较非常非常小心！你是对的：

代码没有做任何有用的事情。 C ++编译器可能足够聪明

来检测只有最外层循环有任何持久效果：它

改变np。如果编译器足够聪明，知道

pc.GetParticle（ps）没有副作用，那么它可能只是简单地消除内部循环

。


你确定在C ++ pc.GetParticle中被称为

次数吗？或者它根本就没有被调用过吗？


然后它可能只是C ++编译器生成更好的代码。但是，你不能仅仅通过这样的基准来判断

而无需进一步检查。

< ia * ******@bmtcordah.com> écritdansle message de news：
11**********************@i40g2000cwc.googlegroups。 com ...


|我这里有一小部分代码。当button1_Click时是

|称性能相当差（~0.5秒）。唯一的事就是我是

|没有真正做任何事情！在C ++中，同样的事情需要~0秒才能获得
|执行！！。列表< Pumpicle>比ArrayList快，我转换

|访问前列表到数组。它似乎就像

|从Pumpicle类拆箱双打。任何想法??


1.为什么在访问之前将列表转换为数组？这需要时间!!


2.你没有取消任何东西，因为你持有双打和检索

双打。


而不是你的PumpicleContainer类，只需使用List< Pumpicle>因为它是没有任何包装类的
，看看是否有任何区别。


Joanna


-

Joanna Carter [TeamB]

顾问软件工程师

I have a small sellection of code here. When the "button1_Click" is
called the performance is quite poor (~ 0.5 sec). Only thing is I am
not really doing anything!! In C++ the same thing takes ~ 0 seconds to
execute!!. The List<Pumpicle> is faster than ArrayList and I convert
the List to an array before access. It just seems to be something like
unboxing the doubles out of the Pumpicle class. Any ideas??

PumpicleContainer pc = null;

private void Form1_Load(object sender, EventArgs e)
{
pc = new PumpicleContainer();

for (int i = 0; i < 10000; i++)
{
pc.Add(new Pumpicle());
}

pc.ToArray();
}

public class DaublePoint
{
public double m_x;
public double m_y;
public double m_z;
};

public class Pumpicle
{
public DaublePoint m_pos;
public double m_mass;

public Pumpicle()
{
m_pos = new DaublePoint();
}
};

class PumpicleContainer
{
public List<Pumpicle> m_pList = new List<Pumpicle>();

Pumpicle[] m_arr = null;

public void Add(Pumpicle p)
{
m_pList.Add(p);
}

public void ToArray()
{
m_arr = m_pList.ToArray();
}

public Pumpicle GetParticle(int i)
{
return m_arr[i];
}
}

private void button1_Click(object sender, EventArgs e)
{
pc.ToArray();

long start = System.DateTime.Now.Ticks;

int np = 0;
for (int idx = 0; idx < 20; idx++)
{
np += 22;
for (int i = -33; i <= 33; i++)
{
for (int j = -33; j <= 33; j++)
{
for (int l = 0; l < 5; l++)
{
for (int ps = 0; ps < np; ps++)
{
Pumpicle p = pc.GetParticle(ps);

DaublePoint pt = p.m_pos;
double x = pt.m_x;
double y = pt.m_y;
double z = pt.m_z;
}
}
}
}
}

long end = System.DateTime.Now.Ticks;

MessageBox.Show("Finished = " + ((end - start) / 1e7));
}

解决方案

I notice a couple of things.

you''re doing 448900 iterations through those nested for loops (and I''m
not even counting the ps < np loop - who knows what that adds on).

You''re measuring time incorrectly. instead of
System.DateTime.Now.Ticks, use System.DateTime.Now in both places. Then
subtract them and arrive at a TimeSpan, then call elapsedMillis() on the
TimeSpan object. The way you measure it now, if you happen to cross a
second boundary, you could wind up with very inconsistent execution times.

DateTime then = System.DateTime.Now;
// your loop here.
DateTime now = System.DateTime.Now;
TimeSpan ts = now - then;
Console.WriteLine(ts.TotalMilliseconds);

Jeremiah

ia*******@bmtcordah.com wrote:

I have a small sellection of code here. When the "button1_Click" is
called the performance is quite poor (~ 0.5 sec). Only thing is I am
not really doing anything!! In C++ the same thing takes ~ 0 seconds to
execute!!. The List<Pumpicle> is faster than ArrayList and I convert
the List to an array before access. It just seems to be something like
unboxing the doubles out of the Pumpicle class. Any ideas??

PumpicleContainer pc = null;

private void Form1_Load(object sender, EventArgs e)
{
pc = new PumpicleContainer();

for (int i = 0; i < 10000; i++)
{
pc.Add(new Pumpicle());
}

pc.ToArray();
}

public class DaublePoint
{
public double m_x;
public double m_y;
public double m_z;
};

public class Pumpicle
{
public DaublePoint m_pos;
public double m_mass;

public Pumpicle()
{
m_pos = new DaublePoint();
}
};

class PumpicleContainer
{
public List<Pumpicle> m_pList = new List<Pumpicle>();

Pumpicle[] m_arr = null;

public void Add(Pumpicle p)
{
m_pList.Add(p);
}

public void ToArray()
{
m_arr = m_pList.ToArray();
}

public Pumpicle GetParticle(int i)
{
return m_arr[i];
}
}

private void button1_Click(object sender, EventArgs e)
{
pc.ToArray();

long start = System.DateTime.Now.Ticks;

int np = 0;
for (int idx = 0; idx < 20; idx++)
{
np += 22;
for (int i = -33; i <= 33; i++)
{
for (int j = -33; j <= 33; j++)
{
for (int l = 0; l < 5; l++)
{
for (int ps = 0; ps < np; ps++)
{
Pumpicle p = pc.GetParticle(ps);

DaublePoint pt = p.m_pos;
double x = pt.m_x;
double y = pt.m_y;
double z = pt.m_z;
}
}
}
}
}

long end = System.DateTime.Now.Ticks;

MessageBox.Show("Finished = " + ((end - start) / 1e7));
}

ia*******@bmtcordah.com wrote:

Only thing is I am not really doing anything!! In C++ the same thing takes ~ 0 seconds to execute!!. int np = 0;
for (int idx = 0; idx < 20; idx++)
{
np += 22;
for (int i = -33; i <= 33; i++)
{
for (int j = -33; j <= 33; j++)
{
for (int l = 0; l < 5; l++)
{
for (int ps = 0; ps < np; ps++)
{
Pumpicle p = pc.GetParticle(ps);

DaublePoint pt = p.m_pos;
double x = pt.m_x;
double y = pt.m_y;
double z = pt.m_z;
}
}
}
}
}

Be very, very careful about comparisons like this! You are right: the
code isn''t doing anything useful. The C++ compiler may be smart enough
to detect that only the outermost loop has any lasting effect: it
changes np. If the compiler is clever enough to know that
pc.GetParticle(ps) has no side-effects, then it may simply eliminate
the inner loops altogether.

Are you sure that in C++ pc.GetParticle is being called the number of
times you expect? Or is it never called at all?

Then again it may simply be that the C++ compiler produces much better
code. However, you can''t tell just from doing a benchmark like this
without further checks.

<ia*******@bmtcordah.com> a écrit dans le message de news:
11**********************@i40g2000cwc.googlegroups. com...

|I have a small sellection of code here. When the "button1_Click" is
| called the performance is quite poor (~ 0.5 sec). Only thing is I am
| not really doing anything!! In C++ the same thing takes ~ 0 seconds to
| execute!!. The List<Pumpicle> is faster than ArrayList and I convert
| the List to an array before access. It just seems to be something like
| unboxing the doubles out of the Pumpicle class. Any ideas??

1. Why convert the list to an array before access ? this takes time !!

2. You are not unboxing anything as you are holding doubles and retrieving
doubles.

Instead of your PumpicleContainer class, just use a List<Pumpicle> as it is
without any wrapper class and see if that makes any difference.

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer

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