C / C++ / MFC

jhwurmbach wrote:

You see, std::map is quite helpful here, providing you with elegant and easy to read code.

int * histogram = new int[256 * 256 * 256];
memset(histogram, 0, 256 * 256 * 256 * sizeof(int));

for (int x=0;x< w;x++) 
  for (int y=0;y< h;y++)
  {
    histogram[(int)RGB(pixel.Red, pixel.Green, pixel.Blue)]++;
    pixel++;
  }

Chris Losinger wrote:

maybe, but it will be very very slow

jhwurmbach wrote:

May or may not.

jhwurmbach wrote:

You are newing 28MB in one piece here

jhwurmbach wrote:

AND you are still limited to 8-bit per color.

typedef std::map< int, int> HistoMapT ;

const int w = 1000;
const int h = 1000;

BYTE *p = = new BYTE[w * h * 3];

// init to a gradient (also ran init'd to 0s)
for (int x=0;x< w;x++)
{
	for (int y=0;y< h;y++)
	{
		p[x * 3 + y * w * 3 + 0] = x % 256;
		p[x * 3 + y * w * 3 + 1] = y % 256;
		p[x * 3 + y * w * 3 + 2] = (x + y) % 256;
	}
}


{
	CTimer c("Map"); // TRACE's time elapsed from construction to destruction
	BYTE * pix = p;
	HistoMapT theMap;

	for (int x=0;x< w;x++)
	{
		for (int y=0;y< h;y++)
		{
			int color_number = RGB(pix[0], pix[1], pix[2]);
			HistoMapT::iterator theIterator = theMap.find(color_number);
			int value = 1;
				
			if (theIterator != theMap.end() ) 
			{
				value += (*theIterator).second;
			}
			theMap.insert(std::pair< int, int>(color_number, value));

			pix+=3;
		}
	}
}

{	
	CTimer c("C");
	BYTE * pix = p;
	int *histo = new int[256 * 256 * 256];
	memset(histo, 0, 256 * 256 * 256 * 4);
	for (int x=0;x< w;x++)
	{
		for (int y=0;y< h;y++)
		{
			histo[RGB(pix[0], pix[1], pix[2])]++;
			pix+=3;
		}
	}

	delete [] histo;
}

delete [] p;

Chris Losinger wrote:

64MB. [...]Your map will potentially require many times more than that.

Chris Losinger wrote:

true. it's an easy enough problem to fix.

Chris Losinger wrote:

i ran the timing tests

jhwurmbach wrote:

From your test-code I got 56msec vs. 85 msec for the map.

jhwurmbach wrote:

Thats factor 1.5
I'm still unimpressed.

Chris Losinger wrote:

debug or release

Chris Losinger wrote:

if only my customers were so ambivalent about performance!

// _Template.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "Windows.h"
#include "MMSystem.h"
#pragma comment( lib, "winmm")

#include <tchar.h>
#include <iostream>
#include <map>
#include <hash_map>

#undef max
#undef min

static const int TARGET_RESOLUTION = 1;// 1-millisecond target resolution

int _tmain(int argc, _TCHAR* argv[])
{
	typedef std::map<int, int> HistoMapT ;
	typedef stdext::hash_map< int, int> HashHistoMapT;
	typedef std::pair<int, int> Int_PairT;

	const int w = 1000;
	const int h = 1000;

	//Init Multimedia timer
	TIMECAPS tc = {0};
	UINT     wTimerRes = 5; //default

	if( ::timeGetDevCaps( &tc, sizeof(TIMECAPS)) != TIMERR_NOERROR) 
	{
		std::cout << "Timer Error";
		return system("pause");
	}

	wTimerRes = std::min( std::max( tc.wPeriodMin, (UINT)TARGET_RESOLUTION), tc.wPeriodMax);
	::timeBeginPeriod( wTimerRes); 

	// init to a gradient (also ran init'd to 0s)
	BYTE *p = new BYTE[w * h * 3];
	for (int x=0; x< w;x++)
	{
		for (int y=0;y< h;y++)
		{
			p[x * 3 + y * w * 3 + 0] = w % 256;
			p[x * 3 + y * w * 3 + 1] = h % 256;
			p[x * 3 + y * w * 3 + 2] = (w + h) % 256;
		}
	}

	//Timing of std::map
	const UINT before1 = ::timeGetTime();
	{
		BYTE * pix = p;
		HistoMapT theMap;

		for (int x=0;x< w;x++)
		{
			for (int y=0;y< h;y++)
			{
				const int color_number = RGB(pix[0], pix[1], pix[2]);
				HistoMapT::iterator theIterator = theMap.find(color_number);
				int value = 1;
				if (theIterator != theMap.end() ) 
				{
					value += (*theIterator).second;
				}
				theMap.insert(Int_PairT(color_number, value));

				pix+=3;
			}
		}
	}
	const UINT after1 = ::timeGetTime();

	//Timing of stdext::hash_map
	const UINT before2 = ::timeGetTime();
	{
		BYTE * pix = p;
		HashHistoMapT theMap;

		for (int x=0;x< w;x++)
		{
			for (int y=0;y< h;y++)
			{
				const int color_number = RGB(pix[0], pix[1], pix[2]);
				HashHistoMapT::iterator theIterator = theMap.find(color_number);
				int value = 1;
				if (theIterator != theMap.end() ) 
				{
					value += (*theIterator).second;
				}
				theMap.insert(Int_PairT(color_number, value));

				pix+=3;
			}
		}
	}
	const UINT after2 = ::timeGetTime();

	//Timing of C-Array
	const UINT before3 = ::timeGetTime();
	{	
		BYTE * pix = p;
		int *histo = new int[256 * 256 * 256];
		memset(histo, 0, 256 * 256 * 256 * sizeof(histo[0]));
		for (int x=0;x< w;x++)
		{
			for (int y=0;y< h;y++)
			{
				histo[RGB(pix[0], pix[1], pix[2])]++;
				pix+=3;
			}
		}

		delete [] histo;
	}
	const UINT after3 = ::timeGetTime();

	delete [] p;

	::timeEndPeriod( wTimerRes);
	std::cout << "Elapsed timing map: " << (after1 - before1) << " msec." << std::endl;
	std::cout << "Elapsed timing hash_map: " << (after2 - before2) << " msec." << std::endl;
	std::cout << "Elapsed timing C-Code: " << (after3 - before3) << " msec." << std::endl;

	return system("pause");
}

Chris Losinger wrote:

Elapsed timing map: 1002 msec.
Elapsed timing hash_map: 1887 msec.
Elapsed timing C-Code: 120 msec.
Press any key to continue . . .

jhwurmbach wrote:

Are you still in Debug?

CWnd *pWnd  = CWnd::FindWindow(_T("WMPlayerApp"),NULL);
CMenu *pMenu =  pWnd->GetMenu();
if (pMenu != NULL && pMenu->GetMenuItemCount() > 0) // make sure there is a menu
{
CMenu * pSubMenu = pMenu->GetSubMenu (0); // Gets the submenu at nItem (starts at 0)
if (pSubMenu != (CMenu *)NULL) // make sure there is a submenu
{
pSubMenu->EnableMenuItem (nMenuItemID, MF_GRAYED|MF_BYCOMMAND); // disables the menuitem
}
}

Sethuraman.K wrote:

For example, Inside a Dialog i have 3 edit controls. If i want to update all 3 controls, i will call UpdateData(True). If, i want to update only a particular contol value(i.e. i don't want to update remaining 2 controls value). how is it possible?


Sethuraman.K