|
I am using the VC version, never gave it a thought. What other implementations have you worked with?
|
|
|
|
|
You are talking about arrays, but your sample uses std::list 
Maybe you should change your code to following:
std::list<int> FooList()
{
std::list<int> list;
for(int x = 0; x < 50; x++)
list.push_back(x);
return list;
}
Regards
Thomas
Finally with Sonork id: 100.10453 Thömmi
Disclaimer:
Because of heavy processing requirements, we are currently using some of your unused brain capacity for backup processing. Please ignore any hallucinations, voices or unusual dreams you may experience. Please avoid concentration-intensive tasks until further notice. Thank you.
|
|
|
|
|
There is no way in hell a container class could ever be as optimized as an unbounded, well defined array fill.
Here are some of the differences between your FooArray and FooList.
1. As someone else pointed out, you are using a list and not a vector. A vector would be a more valid test.
2. std::vector does bounds checking and reallocates the data buffer using a doubling algorithm. Your FooArray routine does no bounds checking and is limited to only 50 elements.
3. Passing the list (or vector) is just a bit slower. You can double the performance by passing in a destination list into the routine via a reference.
4. Only runing the routine once is not a valid test. In my tests in release mode, executing each routine 10000 times yielded this information:
list - 6770 ms
vector - 841 ms
array - 30 ms
With the optimization of passing the list and vector into the routine:
list - 3175 ms
vector - 811 ms
array - 30 ms
If you don't destruct the list or vector each loop iteration and just invoke .clear on them, the numbers are as follows:
list - 3090 ms
vector - 290 ms
array - 30 ms
The final optimization I can think of is pre allocating the vector to size 50. However, that change made no difference. The reason being that the clear routine just sets the size back to zero and doesn't deallocate the vector data. Thus, since after the first pass the vector is already sized to 50, invoking reserve to preallocate the vector to 50 does nothing. Which shows the cost of all the memory allocation in vector. 800+ ms to 300 by removing all the allocations. Thus, vector has 270 ms of bookkeeping overhead that FooArray doesn't have.
5. Most optimizers can not handle deeply nested inlining well. It is very easy to optimize the hell out of FooArray. However, the compiler has much more trouble optimizing FooList since the implementation is deeply nested and more complex.
Tim Smith
Descartes Systems Sciences, Inc.
|
|
|
|
|
Great comments.
I wanted to point out on #2 that bounds checking with vector only happens if you use .at(). For the regular [] index method, there is no bounds checking with vector.
CodeGuy
The WTL newsgroup: over 1100 members! Be a part of it. http://groups.yahoo.com/group/wtl
|
|
|
|
|
Ah, you are right. I didn't know that.
Tim Smith
Descartes Systems Sciences, Inc.
|
|
|
|
|
I appreciate your comments.
Tim Smith wrote:
There is no way in hell a container class could ever be as optimized as an unbounded, well defined array fill.
I never expected to be able to accomplish this, merely get a little closer in performance. Using a vector instead of list does that. Wrong container on my part.
Tim Smith wrote:
2. std::vector does bounds checking and reallocates the data buffer using a doubling algorithm. Your FooArray routine does no bounds checking and is limited to only 50 elements.
Of course FooArray is only limited to 50 and does no bounds checking. This was only a simple example. Don't take it so seriously.
Tim Smith wrote:
4. Only runing the routine once is not a valid test. In my tests in release mode, executing each routine 10000 times yielded this information:
Who says I ran the test only once? I didn't think it necessary to post the results of each test run, only one to give as an example.
|
|
|
|
|
My point was that lists and vectors provide a rich feature set which have to come at some cost. From your reply it is obvious to me now this was something that you already understood. In the past I have run into many people who didn't understand this and thus the reason for my point.
As far as running the test routines multiple times, I was just trying to figure out why in your test, the list was a magnitude slower than the list in my tests. Maybe it was causes by differences between VC STL and STLPort that I use. I was thinking that you didn't run the test routines enough times in a tight loop. Another cause could have been debug instead of release build.
Tim Smith
Descartes Systems Sciences, Inc.
|
|
|
|
|
Why are you comparing apples and oranges? You need to compare vectors with arrays.
A fair comparison would be the following:
std::vector<int> FooVector()
{
std::vector<int> v(50);
for (int i=0; i<50; i++)
v[i] = i;
return v;
}
Also, on VC++, Herb Sutter has proved that deque is actually faster than vector, so you might consider trying comparisons with that as well.
CodeGuy
The WTL newsgroup: over 1100 members! Be a part of it. http://groups.yahoo.com/group/wtl
|
|
|
|
|
Hmm, I am going to have to look into DeQue and see how it stores the data (thus getting an idea of how it impacts resources and such.)
If you had to describe the data storage of DeQue in 100 words or less, how would you describe it?
Tim Smith
Descartes Systems Sciences, Inc.
|
|
|
|
|
Deque = double-ended queue.
It has the same basic functionality as vector, except it also has push_front function, for pushing data onto the front of the queue.
If you are interested in the Sutter article, it can be found at
http://www.gotw.ca/gotw/054.htm
CodeGuy
The WTL newsgroup: over 1100 members! Be a part of it. http://groups.yahoo.com/group/wtl
|
|
|
|
|
Ah, my first best guess was that deque was using some form of buckets. 
It did look like his article didn't show that deques were faster than vectors, unless you used vectors in manners that specifically designed to perform better with deque (head inserts and deletes).
BUT, one thing I did like about deque is that it will generally have less wasted memory.
Tim Smith
Descartes Systems Sciences, Inc.
|
|
|
|
|
You're exactly right -- I didn't read the article closely enough. The performance advantages only come into play when you said: head inserts and deletes, which may not be necessary for most typical vector operations. Looking more closely, I guess his point was that deque was a better general-purpose container than a vector.
Thanks for keeping me straight.
CodeGuy
The WTL newsgroup: over 1100 members! Be a part of it. http://groups.yahoo.com/group/wtl
|
|
|
|
|
Thanks, I guess wrong choice of containers on my part.
|
|
|
|
|
I am trying to get a picture control to work in win 95.
This is the code that loads the code:
HBITMAP hbm = (HBITMAP)::LoadImage(AfxGetApp()->m_hInstance, MAKEINTRESOURCE(m_nBitmap), IMAGE_BITMAP, 0, 0, LR_LOADTRANSPARENT);
m_nBitmap is a UINT value containing the resource ID. It works in Windows XP but in 95 it just doesn't show a pic. Is there something wrong with the code?
- Matt Newman
- Matt Newman
-Sonork ID: 100.11179:BestSnowman
|
|
|
|
|
Check the resolution in Win95. If your controls size is smaller than a picture, it won't show it
Same code working fine in Win2000 and 98
Philip Patrick
"Two beer or not two beer?" <shakesbeer>
Web-site: www.saintopatrick.com
|
|
|
|
|
Yep some of the pictures were differnt sizes. Fixed that.
- Matt Newman
- Matt Newman
-Sonork ID: 100.11179:BestSnowman
|
|
|
|
|
Does anyone knows where can I get a program like api guide. What it does is that it shows all the Visual C++ api samples & coding for each single api. 
|
|
|
|
|
Buy Win32 API super bible by Richard Simon [it has a CD with it that has all the source code examples]
Nish
Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut
|
|
|
|
|
The Platform SDK does a good job of providing samples for Microsoft Windows APIs.
Michael 
|
|
|
|
|
I was wondering if there is anyway to format text (actually all I need to do is cat text) in an edit box.
For example:
I have a read-only edit box that is supposed to display text entered into other edit controls. Using SetWindowText(), I am able to successfully populate the read-only edit box with text from 1 of the other edit boxes. But when I try to use SetWindowText() with the others, it writes over all the previous text from the other controls, obviously. I attempted to use a Rich edit control, but for some strange reason, the code compiles fine but the executable just won't run. As soon as I took the Rich Edit out of the program, it ran fine. I don't really need all the "bells and whistles" that a Rich Edit control provides, I just need to be able to concatenate text in a simple edit control.
Jeez, this didn't come out too understandable. Sounded better in my head, don't know of anyway else to describe it though.
I hope someone can help.
Thanks in advance!
Digital Khaos
"Every problem has a solution"
|
|
|
|
|
First you setsel with the length of the text in the edit box as both beginning and end, then you replacesel with the text you want to concatenate.
Christian
I have come to clean zee pooollll. - Michael Martin Dec 30, 2001
Sonork ID 100.10002:MeanManOzI live in Bob's HungOut now
|
|
|
|
|
When I put microsoft software into the CD drive, the CD automatically starts spinning and something will pop up so I can begin installing the software.
When I put my software into a CD drive, nothing happens. How do I make the CD automatically execute the setup.exe?
Please, any response any one can give me will be greatly appreciated.
Sincerely,
Danielle (an overworked graduate student)
|
|
|
|
|
You need to make an autorun.ini. I don't remember the exact sytax of the file off the top of my head, but if you take one of those CD's that does it and look at the file, it's very obvious.
Are you sure you want it to run setup automatically? A lot of those CD's have an autorun.exe that is simply a menu that can execute the setup. That way it doesn't start to install every time you put the CD in.
Programming in binary is as easy as 01 10 11.
|
|
|
|
|
Greven wrote:
You need to make an autorun.ini
Actually it is autorun.inf
Nish
Sonork ID 100.9786 voidmain
www.busterboy.org
If you don't find me on CP, I'll be at Bob's HungOut
|
|
|
|
|
From the MSDN:
The minimalist AUTORUN.INF file only needs to contain three lines of text:
[autorun]
open=filename.exe
icon=filename.ico
Best Regards
Carlos Antollini.
Sonork ID 100.10529 cantollini
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
