Re: Visual Studio C++ compiler empty functions - C / C++ / MFC Discussion Boards

lor7526-Mar-15 1:10

26-Mar-15 1:10

Hello,

i'm quite new to MFC programming and I would like if my software architecture can be simplified.

Let's suppose to have an MFC program where I put a member variable in CView class. This variable is set by a control put in a dialog window called by a menù.
I usually set a control variable in order to get the control value in order to avoid the GetdlgItem command.
The value of the control is used to set a member variable inside tha class of the dialog window and then when i close the dialog I copy the value of the dialog's variable into the main window variable

control variable -> member variable of the dialog window -> member variable of the main Cview window

With this scheme I Have to use 3 variables for each controls and this is quite expensive.
Can anyone suggest me a simpler way to get to synchronize the variable used by the main window with the value of a control inside a dialog window?

Best regards.

Re: Controls, variable and dialogs

David Crow26-Mar-15 3:26

David Crow

26-Mar-15 3:26

As I understand your problem, two variables are needed: one used by the dialog class, and the other used by the view class.

"One man's wage rise is another man's price increase." - Harold Wilson

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Re: Controls, variable and dialogs

lor7526-Mar-15 4:19

lor75

26-Mar-15 4:19

Yes, two variables. But I don't know if there is a better way to get the same result.

Re: Controls, variable and dialogs

Freak3030-Mar-15 1:22

Freak30

30-Mar-15 1:22

If you are worried about the memory needed to store several values twice, you could define a class or struct, create an object of it in your view class and pass the reference to this object to the dialog objects in their constructors. This way you only have 4 byte overhead per dialog.

The good thing about pessimism is, that you are always either right or pleasently surprised.

win32 - how avoid flickers?

Member 1154582425-Mar-15 11:50

Member 11545824

25-Mar-15 11:50

for avoid flickers i must do:
1 - use the WS_CLIPCHILDREN on parent window;
2 -

C++

case WM_ERASEBKGND:
                {
                    return (LRESULT) 1;
                }
                break;

seems be used only on parent window too.
the child controls are transparent:
(i use the button class for create a label. why?!? because be correctly transparent using the BS_OWNERDRAW style.)

C++

case WM_ERASEBKGND:
            {
                return (LRESULT)1;
            }
            break;

            case WM_CTLCOLORSTATIC:
            {
                return (LRESULT)GetStockObject(NULL_BRUSH);
            }
            break;
            case WM_PAINT:
            {
                PAINTSTRUCT test;
                BeginPaint(hwnd, &test);
                image imglabel(test.rcPaint.right-test.rcPaint.left,test.rcPaint.bottom - test.rcPaint.top);
                brush brshbackcolor(inst->clrBackColor);
                brshbackcolor.ToDC(imglabel);
                brush brshTransparent;

                FillRect(imglabel,&test.rcPaint,brshbackcolor);
                if(inst->imgtest.haveimage())
                    DrawHICONtoHDC(imglabel, inst->imgtest,1,1);
                SetBkMode(imglabel,TRANSPARENT);
                char *text=(char*)inst->strCaption.c_str();
                SetTextColor(imglabel,inst->clrTextColor );
                DrawTextEx(imglabel,text,-1,&test.rcPaint,DT_LEFT,NULL);
                if(inst->blnBorder==true)
                    DrawEdge(imglabel, &test.rcPaint,BDR_SUNKENINNER | BDR_RAISEDOUTER,BF_RECT);
                TransparentBlt(test.hdc,0,0,test.rcPaint.right,test.rcPaint.bottom,imglabel,0,0,test.rcPaint.right,test.rcPaint.bottom, inst->clrBackColor);
                //BitBlt(test.hdc,0,0,test.rcPaint.right,test.rcPaint.bottom,imglabel,0,0, SRCCOPY);
                EndPaint(hwnd, &test);
                return 0;
            }
            break;

and the how i readraw the window:

C++

RECT d;
                GetClientRect(hwnd,&d);
                RedrawWindow(hwnd,&d,nullptr,RDW_UPDATENOW | RDW_INVALIDATE | RDW_ERASENOW);

but when, with animation\timer, the next image is drawed above the older one, instead clean all control and then redraw it.
(i need avoid the flicker and draw the control correctly and not 1 image above other)
can anyone advice me?

Visual Studio C++ compiler empty functions

severin025-Mar-15 10:28

severin0

25-Mar-15 10:28

Does anyone know if the Visual Studio C++ compiler optimizes to eliminate calls to functions with empty definitions (nothing between the curly braces denoting the function's body)?
I am particularly interested in the 2010 and 2012 versions of the Visual Studio compiler.

Thank you.

Re: Visual Studio C++ compiler empty functions

Richard Andrew x6425-Mar-15 15:39

Richard Andrew x64

25-Mar-15 15:39

It would be easy enough for you to find this out for yourself. Create a small test program with such a function, and use Disassembly View to step through the code where the function is called.

OTOH, these are the two optimizations that I do know about:

1. It combines functions that have identical definitions, and
2. It eliminates functions that are never called

Both of these optimizations can be turned off in the Options dialog box.

The difficult we do right away...
...the impossible takes slightly longer.

Re: Visual Studio C++ compiler empty functions

Daniel Pfeffer25-Mar-15 23:00

Daniel Pfeffer

25-Mar-15 23:00

It depends on whether the method is virtual. It would theoretically be possible to eliminate all calls to empty non-virtual methods. A virtual method may be overridden by a derived class, so the compiler must perform the virtual call.

(There may be some cases where the compiler can prove that the virtual call refers to the base class. In this case, the compiler could optimize the call away.)

As Richard suggests, the best way to check this is to write a short test program.

If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.

--Winston Churchill

Re: Visual Studio C++ compiler empty functions

Maximilien26-Mar-15 4:38

Maximilien

26-Mar-15 4:38

Yes, the compiler will eliminate useless calls (maybe not in DEBUG mode, but surely in RELEASE mode).

today's compiler are a lot more smarter than you can imagine.

Is there a particular reason for this question?

I'd rather be phishing!

Unable to get WTS_SESSION_LOGON event notification. How to capture the event when user log on to the machine.?

mbatra3124-Mar-15 0:09

mbatra31

24-Mar-15 0:09

Hi,

I have an application which captures Lock, Unlock, Logoff and Logon events of Windows OS. I am able to get the notifications for Lock, Unlock and Logoff, but not getting any notification when user Logs on to the machine. I am using WTS_SESSION_LOGON event to capture the Log on event.

How to capture the event when user log on to the machine.

Any help will be appreciated.

Regards,

Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

prime_tang23-Mar-15 23:37

prime_tang

23-Mar-15 23:37

The following code is a basic algorithm for hamming distance calculation, but due to the design of my application, it requires many times to use this algorithm, in order to improve application efficiency, I want to improve the efficiency of this algorithm, is there any appropriate methods? Assembly language possible?

C++

unsigned dist(const unsigned char *vec1, const unsigned char *vec2, unsigned dim)
{
    const unsigned char popCountTable[] =
    {
        0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
        3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
    };
    unsigned dist_ = 0;
    for (unsigned i = 0; i != dim; ++i)
    {
        dist_ += popCountTable[vec1[i] ^ vec2[i]];
    }
    return dist_;
}

Re: Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

Richard MacCutchan24-Mar-15 3:40

Richard MacCutchan

24-Mar-15 3:40

You should try at http://www.codeproject.com/Forums/326859/Algorithms.aspx[^], but you will need to provide more details of what this algorithm is doing and why your implementation is slow.

Re: Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

Jochen Arndt24-Mar-15 4:14

Jochen Arndt

24-Mar-15 4:14

I don't see much optimisation options.
You are already using a lookup table and the code should not consume much time when dim is small. Rewriting it in assembler will be probably not faster because modern compilers will generate effective code (you may tell your compiler to generate an assembly output to check this).

When the code should be always executed on modern x86 CPUs, you may replace the popcount lookup with the __popcnt x86 instruction. For MS compilers see https://msdn.microsoft.com/library/bb385231.aspx[^].

[EDIT]
When using the popcnt instruction and your data are always a multiple of 2 or 4 (or 8 with 64-bit builds), you can reduce the number of loop executions by performing the operation with 16/32/64 bits.

Re: Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

C^hris L^osinger24-Mar-15 9:06

C^hris L^osinger

24-Mar-15 9:06

Google says: http://bmagic.sourceforge.net/bmsse2opt.html[^]

image processing toolkits | batch image processing

Re: Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

.Shoaib25-Mar-15 6:35

.Shoaib

25-Mar-15 6:35

I wouldn't recommend assembly, unless platform portability is not a concern. A relatively easier option would be to apply a Duff's device to this loop. Unrolling the loop can provide performance boost. However, unless this is, say DSP code that has to run over and over again its probably not worthwhile and the effects wont be noticable.

http://en.wikipedia.org/wiki/Duff%27s_device[^]

I would recommend to benchmark the code first to establish the base data for performance comparison.

Re: Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

jschell25-Mar-15 10:58

jschell

25-Mar-15 10:58

prime_tang wrote:
but due to the design of my application, it requires many times to use this algorithm

First step would of course be to find a design that doesn't require many uses.

That would have a far more significant impact on any speed up of the actual algorithm.

Re: Is there a way to accelerate the following algorithm for hamming distance calculation? By assembly language?

Stefan_Lang8-Apr-15 4:52

Stefan_Lang

8-Apr-15 4:52

I don't see much optimization potential in your function that a decent compiler won't apply already.

That said, the first question you should ask: is there an actual performance bottleneck? Have you measured the time your application takes, and is it really too slow for your purposes?

Second question: if there is a performance issue, which function is causing it? Maybe there are others called alongside this function that take more time and have more optimization potential? Typically, I/O is the slowest part of any application, so reducing I/O to the absolute minimum could already help.

You say it is called often, so the next question would be: can you reduce the number of calls? You said the number of calls is high due to your application design, this implies a different design would require less calls?

GOTOs are a bit like wire coat hangers: they tend to breed in the darkness, such that where there once were few, eventually there are many, and the program's architecture collapses beneath them. (Fran Poretto)

Link Error Which .lib to include

ForNow21-Mar-15 19:28

ForNow

21-Mar-15 19:28

Hi
I have a Console C project that has a number of DLL's

I got the following error when linking

Quote:
error LNK2001: unresolved external symbol _DllMainCRTStartup@12

I am linking it as 64 bit

How would I know what .lib to include by googling seemed it was MSVCRT.LIB
but that didn't resolve my problem

I remember once using dependency walker to resolve symbols but I think that was looking at .DLL to see what entry points were exposed

Thanks

Re: Link Error Which .lib to include

Richard MacCutchan21-Mar-15 23:58

Richard MacCutchan

21-Mar-15 23:58

Check the documentation for the DLL methods that you are calling. For example Google can find you https://www.google.com/search?q=DllMainCRTStartup[^].

Re: Link Error Which .lib to include

ForNow22-Mar-15 16:50

ForNow

22-Mar-15 16:50

Thank you again Richard the problem was in my win32.mak

I have amd64 cpu and for some reason win32 it was i386 thus generating @12 ordinal for

The DLL startup entry point

still trying to finish building

Re: Link Error Which .lib to include

Frankie-C23-Mar-15 0:36

Frankie-C

23-Mar-15 0:36

So I was right 64bits objs and 32bits linking... Smile | :)

Re: Link Error Which .lib to include

ForNow23-Mar-15 2:10

ForNow

23-Mar-15 2:10

Yes thanks

Re: Link Error Which .lib to include

Frankie-C22-Mar-15 0:19

Frankie-C

22-Mar-15 0:19

If you are linking for 64bits the entry point for dll should be _DllMainCRTStartup (undecorated entry point). If you get this error probably there is a error in linker switches because it seems that you are trying to use 64 bits objects in a 32bits link.
It is not very clear in which part of your project you're getting the error: compiling the console exe or one of the DLL?

modified 22-Mar-15 6:58am.

MALLOC FUNCTION IMPLEMENTATION

Member 1154244420-Mar-15 10:45

Member 11542444

20-Mar-15 10:45

SIR,
I want to define my own malloc function in c++ using new operator..

Re: MALLOC FUNCTION IMPLEMENTATION

PIEBALDconsult20-Mar-15 11:35

PIEBALDconsult

20-Mar-15 11:35

Thanks for the warning. Good luck.

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