C / C++ / MFC

30-Dec-07 8:09

You cannot use that operator, since the CPoint class hasn't it. BTW what you expect that such operator should do in your code?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Game loop

snir_ya30-Dec-07 4:03

snir_ya

30-Dec-07 4:03

Hi all,

I'm writing a game application with a main lobby where players can select a game which opens in a different frame window.

Players can open several games at a time so actually there's only one view that needs to be rendered at a time.

The game loop should respond to key and mouse events using directInput (directX). My question is where do i place the game loop? Should it be in the main application's run method? Should it answer onpaint messages on the currently active view?

Thanks in advnace.

Snir_ya.

Jeremy Falcon30-Dec-07 14:48

Jeremy Falcon

30-Dec-07 14:48

snir_ya wrote:
My question is where do i place the game loop?

This is an open ended question as we don't really know your plan. Are these individual games running in their own process space, in a new thread, or what?

Each game (assuming they are independent) should have its own main loop more times than not - even if they have to interact with one another via IPC or whatever.

Also, don't put your main game loop in WM_PAINT for D3D or DD. It should be independent of GDI operations and either ran in or called from within the process' main loop (e.g.; WinMain(), main(), etc.).

Jeremy Falcon
Oatmeal, It's What's for Dinner.[^]

Mark Salsbery30-Dec-07 14:50

Mark Salsbery

30-Dec-07 14:50

Jeremy Falcon wrote:
don't put your main game loop in WM_PAINT

mmmm...oatmeal...

Happy new year Jeremy!

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Jeremy Falcon30-Dec-07 14:55

Jeremy Falcon

30-Dec-07 14:55

Mark Salsbery wrote:
mmmm...oatmeal...

Mark Salsbery wrote:
Happy new year Jeremy!

You too man! Here's to another great year of procrastination! Laugh | :laugh:

Jeremy Falcon
Oatmeal, It's What's for Dinner.[^]

Mark Salsbery30-Dec-07 15:07

Mark Salsbery

30-Dec-07 15:07

Jeremy Falcon wrote:
Here's to another great year of procrastination!

I'm putting that off for a while...

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Double-Checked Locking pattern issue

snir_ya31-Dec-07 0:19

snir_ya

31-Dec-07 0:19

Cheers Jeremy and Mark - Happy new year to ya too.

George_George30-Dec-07 3:26

30-Dec-07 3:26

Hello gurus,

For the wellknown Double-Checked Locking pattern,

http://www.ddj.com/184405726?pgno=1

Step 1: Allocate memory to hold a Singleton object.
Step 2: Construct a Singleton object in the allocated memory.
Step 3: Make pInstance point to the allocated memory.

After reading for a couple of times, I still do not understand why some compiler will exchange step 2 and step 3 code? If there are any exception in step 2, the swap code will make pInstance point to an invalid memory address. Any ideas why compiler do the swap?

Singleton* Singleton::instance() {
    if (pInstance == 0) {
    Lock lock;
        if (pInstance == 0) {
        pInstance = // Step 3
        operator new(sizeof(Singleton)); // Step 1
        new (pInstance) Singleton; // Step 2
        }
    }
    return pInstance;
}

thanks in advance,
George

CPallini30-Dec-07 3:41

30-Dec-07 3:41

Generally speaking, whenever there isn't a formal specification about the exact implementation detail of a construct, a compiler developer may choose the implemenation he suppose best fullfilling the purpouse.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

George_George30-Dec-07 3:56

30-Dec-07 3:56

Thanks CPallini,

I can understand and agree with you that some compiler will swap and some will not -- implementation dependent. Smile | :)

My question is (I want to understand why it swaps in some compiler's implementation), according to the article, it seems that it describes why compiler swaps step 2 and step 3, but I can not understand the reason after reading it.

This is what the article says about they will describe the reason why compiler swaps the order, but I do not find and understand it. Do you have any ideas, guru? Smile | :)

(In section, 4 DCLP and Instruction Ordering)
--------------------
Why they might want to do that is a question
we’ll address in a moment. For now, let’s focus on what happens if they do.
--------------------

regards,
George

CPallini30-Dec-07 4:09

30-Dec-07 4:09

George_George wrote:
his is what the article says about they will describe the reason why compiler swaps the order, but I do not find and understand it. Do you have any ideas, guru?

Thank you, but, of course, I'm far of being a guru Smile | :)

.
Anyway, I think that authors circumstatiate their affirmation when talk about optimization, i.e. roughly speaking from sentence
Compilers might choose to execute statement...

to

... It should, therefore, not surprise you that they sometimes do.

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

George_George31-Dec-07 3:32

31-Dec-07 3:32

Hi CPallini,

Sorry for my stupid. Smile | :)

I do not quite catch your points below, why because of your points, step 2 and step 3 are swapped?

CPallini wrote:
Compilers might choose to execute statement...

to

... It should, therefore, not surprise you that they sometimes do

regards,
George

CPallini31-Dec-07 3:51

31-Dec-07 3:51

George_George wrote:
Sorry for my stupid.

Oh don't worry about your insistence, maybe I've a naive trust in article authors!
Big Grin | :-D

In the article they explains (in the paragraph I signaled to you) that some compilers may try to optimize code (hopefully for parallelization on the processor pipeline or on different processor cores) that way.

I observed too that, in general, if you don't place strict constraints on your specification then someone surely will realize the requirement in very unexpected way.
Big Grin | :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

George_George31-Dec-07 4:30

31-Dec-07 4:30

Thanks CPallini,

I have re-read the article you quoted. You are right, and this section is about how to utilize multi-processor's capability to make instructions work in parallel.

But, Smile | :)

My question is about instruction re-ordering, not executing in parallel. They are two things. Smile | :)

So, I do not think the section you quoted answers my question. Do you have any ideas why compiler reordering instructions? The only reason I could think of is reorder and make assignment earlier will save one register. I want to learn your points about this.

regards,
George

CPallini31-Dec-07 6:01

31-Dec-07 6:01

George_George wrote:
My question is about instruction re-ordering, not executing in parallel. They are two things.

Maybe (I'm, for sure, not an expert about) such a reordering gives the processor (or the processor cores) the chances to execute more machine code in parallel.

George_George wrote:
So, I do not think the section you quoted answers my question. Do you have any ideas why compiler reordering instructions? The only reason I could think of is reorder and make assignment earlier will save one register. I want to learn your points about this.

The reason can also be the above but, again, I'm not an expert about...

Anyway, remember one of my points: if you give those ( indeed, very smart) people some implementation freedom then you have to expect everything can happen (and the reason maybe well hidden: perhaps that reordering better adhere to their compiler architecture, who knows?)

Happy new year, best wishes, George
Big Grin | :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

George_George31-Dec-07 6:25

31-Dec-07 6:25

Thanks CPallini and the same to you,

Hope we can have a happy post/discussion in 2008 -- with you together. Smile | :)

regards,
George

Sure.

CPallini31-Dec-07 6:28