Re: Which of these methods is more efficient? - C / C++ / MFC Discussion Boards

MikeUofPhx9-May-04 13:41

9-May-04 13:41

Much appreciated. I changed the comments to C syntax. It's true that I'm not doing proper captue yet (the else statements) but I was hoping to find a better way. Rather than change the while statement I just adapted the bottom so subscripts match. I'm going to see if there is some way I could ste this up with a switch statement. Any suggestions (especially for a better way of processing commands) are much appreciated.

<br />
/* Text Adventure-Console.cpp : Defines the entry point for the console application.*/<br />
<br />
#include <stdio.h><br />
#include <stdlib.h><br />
#include <string.h><br />
#include <mbstring.h><br />
#include <dos.h><br />
<br />
#define CR 0x0d<br />
#define ESC 0x1b<br />
#define TAB 0x09<br />
#define LF 0x0a<br />
#define BACKSPACE 0x08<br />
#define NULL 0<br />
#define TRUE 1<br />
#define FALSE 0<br />
#define LENGTH 80<br />
#define COLS 80<br />
#define VIDEO 0x10<br />
#define ROWS 25<br />
#define DELAY 250<br />
#define MROW 12<br />
<br />
void refresh(void);<br />
void process_command(void);<br />
void main_thing(void);<br />
void cls(void);<br />
<br />
/*Variables - global*/<br />
char user_command[250];<br />
char waitkey [10];<br />
char *pch;<br />
/*enum directions {/*<br />
<br />
/* Defenitions - global */<br />
struct map {<br />
	char *name;<br />
	char *description;<br />
	int north;<br />
	int south;<br />
	int west;<br />
	int east;<br />
	int up;<br />
	int down;<br />
	int other;<br />
}; /*Define the Map structure*/<br />
struct map my_map[22] = {<br />
	{"Location0", "Dummy Location", 0,0,0,0,0,0,0},<br />
	{"Location1", "Admissions", 2,0,10,17,0,0,0},<br />
	{"Location2", "Lovely Lounge", 3,1,5,4,0,0,0},<br />
	{"Location3", "Main Hallway", 20,2,6,13,0,0,0},<br />
	{"Location4", "TV Room", 0,0,2,19,0,0,0},<br />
	{"Location5", "Mess Hall", 6,0,12,2,0,0,0},<br />
	{"Location6", "Crafts Room", 0,5,11,3,0,0,0},<br />
	{"Location7", "Therapy Room", 0,0,0,20,0,0,0},<br />
	{"Location8", "Padded Cell", 0,0,20,0,0,0,0},<br />
	{"Location9", "Mike's Room", 0,0,16,0,0,0,0},<br />
	{"Location10", "Nurse's Station", 0,0,0,1,0,0,0},<br />
	{"Location11", "Group Therapy Room", 0,0,0,6,0,0,0},<br />
	{"Location12", "Fenced Patio", 0,0,0,5,0,0,0},<br />
	{"Location13", "Showers", 0,0,3,0,0,0,0},<br />
	{"Location14", "Violent Ward", 0,0,0,21,18,0,0},<br />
	{"Location15", "Honest Politician's Ward", 0,21,0,0,0,0,0},<br />
	{"Location16", "Depressed College Student's Ward", 0,0,21,9,0,0,0},<br />
	{"Location17", "Phone Booth", 0,0,1,0,0,0,0},<br />
	{"Location18", "Secret Ritual Room", 0,0,0,0,0,14,0},<br />
	{"Location19", "Psychiatrist's Lounge", 0,0,4,0,0,0,0},<br />
	{"Location20", "Hallway part 2", 21,3,7,8,0,0,0},<br />
	{"Location21", "Hallway part 3", 15,20,14,16,0,0,0}<br />
	}; /* Instantiate map structure with 19 "Rooms" as my map - 0 is a dummy*/<br />
<br />
/*Set current room*/<br />
int current_room = 1;<br />
<br />
int main(int argc, char* argv[])<br />
{	<br />
/*Displays current stuff*/<br />
	refresh();<br />
	process_command();<br />
<br />
<br />
	return 0;<br />
<br />
}<br />
<br />
void refresh(void)<br />
{<br />
/*Display current room*/<br />
cls();<br />
printf("*** Josh's fantastic escape from the C Sanitarium for burnt out Coderz ***\n");<br />
printf("\n\n");<br />
printf("LOCATION     : %s\n", my_map[current_room].name);<br />
printf("DESCRIPTION  : %s\n",my_map[current_room].description);<br />
printf("WHAT'S HERE  :\n");<br />
printf("VISIBLE EXITS:");<br />
<br />
/*What exits are visible?*/<br />
if (my_map[current_room].north >= 1)<br />
    {<br />
        printf("North ");<br />
    }<br />
<br />
if (my_map[current_room].south >= 1)<br />
    {<br />
        printf(" South ");<br />
    }<br />
if (my_map[current_room].west >= 1)<br />
    {<br />
        printf(" West ");<br />
    }<br />
if (my_map[current_room].east >= 1)<br />
    {<br />
        printf(" East ");<br />
    }<br />
if (my_map[current_room].up >= 1)<br />
    {<br />
        printf(" Up ");<br />
    }<br />
if (my_map[current_room].down >= 1)<br />
    {<br />
        printf(" Down ");<br />
    }<br />
if (my_map[current_room].other >= 1)<br />
    {<br />
        printf(" Other ");<br />
    }<br />
	/*Gets command*/<br />
printf("\n");<br />
printf("\nWhat would you like to do?\n");<br />
<br />
fgets(user_command, sizeof(user_command), stdin);<br />
fflush(stdin);<br />
printf("\n");<br />
}<br />
void process_command(void)<br />
{<br />
	/*Process Command*/<br />
	/*Split in to words*/<br />
	char *words[11];<br />
	int wordnumber = 0;<br />
	char *pch;<br />
	pch = strtok (user_command, " ");<br />
	/*Load the first word*/<br />
	words[wordnumber]=pch;<br />
	/*Load each additional word into words[]*/<br />
	while ((pch != NULL) && (wordnumber < 10))// and word # is acceptable - add later//<br />
	{<br />
	 wordnumber++;<br />
	 words[wordnumber]=pch;<br />
	 pch = strtok (NULL, " ,.");<br />
	}<br />
	/*loop through*/<br />
	/*int count;*/<br />
	/* for(count=1;count<=wordnumber;count++)*/<br />
	/*{*/<br />
	/*Get last character, strcomp with enter, chomp*/<br />
	/*	printf("**%s**\n",words[count]);*/<br />
	/*}*/<br />
	/* */<br />
<br />
	int result;<br />
	char go[] = "go";<br />
	result = _strnicmp(words[1], go, 2 );<br />
<br />
	if (result==0)<br />
	{<br />
	/*go - what direction?*/<br />
	char north[] = "north";<br />
	char south[] = "south";<br />
	char west[] = "West";<br />
	char east[] = "east";<br />
	char up[] = "up";<br />
	char down[] = "down";<br />
	char other[] = "other";<br />
<br />
	int result;<br />
	result = _strnicmp(words[2], north, 5 );<br />
<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].north >= 1)<br />
			{<br />
				current_room = my_map[current_room].north;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		 }<br />
	 result = _strnicmp(words[2], south, 5 );<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].south>= 1)<br />
			{<br />
				current_room = my_map[current_room].south;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		 }<br />
	 result = _strnicmp(words[2], west, 4 );<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].west >= 1)<br />
			{<br />
				current_room = my_map[current_room].west;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		 }<br />
	 result = _strnicmp(words[2],east, 4 );<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].east >= 1)<br />
			{<br />
				current_room = my_map[current_room].east;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		 }<br />
	 result = _strnicmp(words[2], up, 2 );<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].up >= 1)<br />
			{<br />
				current_room = my_map[current_room].up;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		}<br />
	 result = _strnicmp(words[2], down, 4 );<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].down >= 1)<br />
			{<br />
				current_room = my_map[current_room].down;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		}<br />
	 result = _strnicmp(words[2], other, 5 );<br />
		if (result==0)<br />
		{<br />
		/*Legal move?*/<br />
			if (my_map[current_room].other>= 1)<br />
			{<br />
				current_room = my_map[current_room].north;<br />
				/*Update Display*/<br />
				main_thing();<br />
			}<br />
			else<br />
			{printf("Can't go there!\n");<br />
			}<br />
		 }<br />
	}<br />
char blow[]="blow";<br />
result = _strnicmp(words[1], blow, 4 );<br />
if (result==0)<br />
{<br />
	printf("you typed blow");<br />
}<br />
}<br />
void main_thing(void)<br />
{<br />
	refresh();<br />
	process_command();<br />
}<br />
void cls( void )<br />
{<br />
   system("cls");<br />
}<br />

OLE DB 'IColumnsInfo2' problem

KalliMan8-May-04 13:06

KalliMan

8-May-04 13:06

Hello.
I'm writting application which Open an Access database via OLE DB.
And I want to receave all column metadata With 'IColumnsInfo2::GetRestrictedColumnInfo(...)' , but I cannot(or don't know how) implement IColumnsInfo2 with 'IColumnsRowset'.
i.e.
--------------------------------
IColumnsRowset** ppOLEColumnsInfo;
IColumnsInfo2** ppOLEColumnsInfo2;
.............
HRESULT hr = ppOLEColumnsInfo->QueryInterface(IID_IColumnsInfo2,(void**)ppOLEColumnsInfo2)
//and hr == E_NOINTERFACE
--------------------------------
............
If i try to add 'DBPROP_IColumnsInfo2' property while open 'IColumnRrcorset' with 'IOpenRowset::OpenRowset', result is 'DB_S_ERRORSOCCURRED'.
i.e.
--------------------------------
IOpenRowset** ppOLEOpenRowset;
IColumnsRowset** ppOLEColumnsInfo;
..........

DBPROPSET dbPropSet[1];
ULONG cDbPropCount = sizeof(dbPropSet)/sizeof DBPROPSET;

const ULONG cProperties = 1;
DBPROP rgProperties[cProperties];

pPropSet->rgProperties = rgProperties;
pPropSet->cProperties = cProperties;
pPropSet->guidPropertySet = DBPROPSET_ROWSET;

AddProperty(&rgProperties[1] ,DBPROP_IColumnsInfo2,VT_BOOL,VARIANT_TRUE,DBPROPOPTIONS_OPTIONAL);//doesn't work with DBPROPOPTIONS_REQUIRED, too
............
hr = pOLEOpenRowset->OpenRowset(NULL,&dbID,NULL,IID_IColumnsRowset,
1 ,&dbPropSet,(IUnknown **)&pOLEColumnsRowset );

//and hr == DB_S_ERRORSOCCURRED
//and dbPropSet.rgProperties.dwStatus == DBPROPSTATUS_NOTSUPPORTED
--------------------------------
So, how can i implement Rowset which can implement IDBColumnInfo2 ?

thanks at advice:
KalliMan

a

Which of these methods is more efficient?

Joe Smith IX8-May-04 12:48

Joe Smith IX

8-May-04 12:48

Hi all,

This might be a simple question, and you might say that both ways have their own pros and cons (and the pros and cons are so minor, that they are negligible, therefore they are virtually equally efficient). But sometimes I wonder if every single bit of memory and every cpu cycle count, which one is better?

Thanks for any input.

<br />
// myArray is an array of CMyObject<br />
// GetValue() simply returns an int member from CMyObject, no calculation<br />
// method 1<br />
// repetitive calls, but no additional local variable<br />
for(int i=0; i<myArray.GetSize(); i++)<br />
{<br />
if(myArray.GetAt(i).GetValue()==1) { Function1(); }<br />
else if(myArray.GetAt(i).GetValue()==2) { Function2(); } }<br />
else { Function3(); }<br />
}<br />
<br />
// method 2<br />
// no repetitive calls, but additional local variable<br />
for(int i=0; i<myArray.GetSize(); i++)<br />
{<br />
int nValue = myArray.GetAt(i).GetValue();<br />
if(nValue==1) { Function1(); }<br />
else if(nValue==2) { Function2(); }<br />
else { Function3(); }<br />
}<br />

Re: Which of these methods is more efficient?

Gary R. Wheeler8-May-04 13:39

Gary R. Wheeler

8-May-04 13:39

The answer is, it depends Roll eyes | :rolleyes:

.

If the value returned by myArray.GetAt(i).GetValue() is 1, then the two methods will probably have equivalent performance. The fact that you've got a named temporary variable in method 2 doesn't affect the performance, since the compiler generates a temporary variable to hold the return value in method 1.

If the value returned by myArray.GetAt(i).GetValue() is >= 2, method 2 will probably execute faster. In method 1, the compiler will generate two calls to myArray.GetAt(i).GetValue(). Method 2 only uses a single call. The fact that the function call probably returns the same value is irrelevant, since the compiler can not make that assumption, and therefore must generate and execute code for two calls.

If myArray.GetAt(i).GetValue() does not have side effects, then it's safe to assign its value to a temporary and use that, as in method 2.

If myArray.GetAt(i).GetValue() does have side effects (successive calls with the same arguments do not return the same results), then you must use method 1.

Software Zen: delete this;

Re: Which of these methods is more efficient?

Prakash Nadar8-May-04 22:35

Prakash Nadar

8-May-04 22:35

...but i would like to add

for(int i=0; i<myArray.GetSize(); i++)

myArray.GetSize() is called in every loop, so there is another method call in every loop. you can avoid that by using a temp variable there if the count/loop is large.

I'll write a suicide note on a hundred dollar bill - Dire Straits

Re: Which of these methods is more efficient?

Paul Ranson9-May-04 1:15

Paul Ranson

9-May-04 1:15

Joe Smith IX wrote:

for(int i=0; i<myArray.GetSize(); i++)
{
   int nValue = myArray.GetAt(i).GetValue();
   if(nValue==1) { Function1(); }
   else if(nValue==2) { Function2(); }
   else { Function3(); }
}

How about,

int size = myArray.GetSize ();
for ( int i = 0; i < size; ++i )
{
   switch ( myArray.GetAt ( i ).GetValue ())
   {
      case 1 :
         Function1 () ;
         break ;
      case 2 :
         Function2 () ;
         break ;
      default :
         Function3 () ;
         break ;
   }
}

But if efficiency is relevant the whole structure needs examination.

Paul

Re: Which of these methods is more efficient?

Ravi Bhavnani9-May-04 4:29

Ravi Bhavnani

9-May-04 4:29

Method (1) is dangerous - it requires that GetValue() has no side-effects. This makes for code that's hard to maintain.

/ravi

My new year's resolution: 2048 x 1536
Home | Articles | Freeware | Music
ravib@ravib.com

Re: Which of these methods is more efficient?

Joe Woodbury9-May-04 7:59

Joe Woodbury

9-May-04 7:59

First, the line else if(myArray.GetAt(i).GetValue()==2) { Function2(); } } has an extra brace at the end.

In actual performance the two are identical since they compile to the same thing (at least in VC++ 7.1, but likely also in VC++ 6.0.)

Incidentally, using a switch statement is slightly slower. If there were additional cases, that could change.

[EDIT: At Tim correctly points out, my answer is correct only to the narrow stipulation given. Since GetValue() could involve more than the return of a simple value, it is best to get the value first then test it. The exception would be IF side effects are documented and each test depends on those side effects, though that would be a very odd solution indeed.]

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Re: Which of these methods is more efficient?

Tim Smith9-May-04 9:23

Tim Smith

9-May-04 9:23

What if the definition of GetValue is in another CPP module? Depending on the link time optimization, that code might not be hoisted into the main routine. Thus the multiple GetValue version would not result in the same code.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: Which of these methods is more efficient?

Joe Woodbury9-May-04 9:42

Joe Woodbury

9-May-04 9:42

That wasn't part of his stipulated conditions.

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Re: Which of these methods is more efficient?

Tim Smith9-May-04 13:47

Tim Smith

9-May-04 13:47

Nor was the implementation of the routine being inside the same cpp or made inline.

The only reason I bring this up is because you don't tell the full story. What you said is totally true but only under certain conditions.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Re: Which of these methods is more efficient?

Tim Smith9-May-04 9:27

Tim Smith

9-May-04 9:27

In general, you should use the second version.

When you have full knowledge of how GetValue is implemented, you can decide which is better. However, that makes caller dependent on the implementation of GetValue. If you ever need to change the implementation, any performance decisions might come back to haunt you. You really shouldn't be depending on GetValue being implemented as it is. Thus that makes the second version the better option.

You should always try to keep relationships between two classes limited to interface only and never the actual implementation. You can't always do this, but when you can, it is best that you do.

Tim Smith

I'm going to patent thought. I have yet to see any prior art.

Using MFC Source Code Question

nm_1148-May-04 8:26

nm_114

8-May-04 8:26

Is it free to use the MFC source code however you want, or is that off limits. I don't want to use MFC, but I would like to use bits and pieces of it, like CRect etc. Is this legal, or is it violating any copyrights?

Re: Using MFC Source Code Question

Joe Woodbury8-May-04 8:41

Joe Woodbury

8-May-04 8:41

It's completely legal on the condition that you don't use it to write, and I presume sell, a class library or otherwise represent the code as your own.

Microsoft also requests that you don't compile the new results with the same name as the current MFC libraries.

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

RPC: Problem in sending data

ahsan_a8-May-04 8:17

ahsan_a

8-May-04 8:17

Hi All,

I am trying to send data from my client to my server through an RPC call in Unix C. I am getting following error:

ServerNameHere: RPC: Unable to send; errno = Bad file number; Illegal file descriptor

I am unaware of nitty gritties of RPC, can anyone help?
I need urgent help. Thanks in advance for any help provided.

Just to elloborate on problem, this error normally comes when I try sending some data 2nd time. I am sending different data each time(taken by user input) in a loop.
Regards,
Ahsan

Re: RPC: Problem in sending data

ahsan_a8-May-04 12:03

ahsan_a

8-May-04 12:03

Knock Knock...
Anybody home? Someone please answer.

Re: RPC: Problem in sending data

Gary R. Wheeler8-May-04 13:42

Gary R. Wheeler

8-May-04 13:42

This is a Visual C++ forum on a site with an almost exclusive Microsoft bias. You're not likely to get help with a UNIX RPC problem here, I'm afraid.

Software Zen: delete this;

Access WindowProc in MFC?

Anonymous8-May-04 7:04

Anonymous

8-May-04 7:04

I am a newb to programming, so I use the MFC wizard in VC++ 2003. I would like to have access to the WindowProc function (the function that recieves all the messages), but it is locked. Does anyone know how I could edit the WindowProc function? Anyone that could help, that would be great.

Void

soul.ripper8-May-04 7:03

soul.ripper

8-May-04 7:03

I need stop the program,

<br />
<br />
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {<br />
	if (stricmp(lpCmdLine, "-noautorun") == 0) {<br />
		autorun(); <br />
i cant juse break; <br />
    <br />
	}else if (lpCmdLine == NULL || _tcslen(lpCmdLine) == 0) {<br />
<br />
    MessageBox(NULL, _T("No switch specified"), g_pszCaption, MB_OK | MB_ICONEXCLAMATION);<br />
    return 0;<br />
  }<br />
<br />
void autorun(){<br />
if void autorun() ends, <br />
the program needs to stop running <br />
<br />
i cant juse return 0;<br />
<br />
// terminate the program:<br />
  return 0;<br />
}<br />
error C2562: 'autorun' : 'void' function returning a value<br />
<br />

thanx for helping me

Greets Jeroen Big Grin | :-D

Re: Void

Ryan McDermott8-May-04 7:08

Ryan McDermott

8-May-04 7:08

Obviously voids can't return a value but I think you could use ExitProcess API or maybe TerminateProcess API. Try this link

-Ryan M.

Re: Void

soul.ripper8-May-04 8:17

soul.ripper

8-May-04 8:17

Thanx ryan M.

<br />
void autorun () {<br />
<br />
// terminate the program:<br />
ExitProcess(0); <br />
}}<br />

Jeroen .b

Re: Void

toxcct9-May-04 10:27

toxcct

9-May-04 10:27

don't exit() function work too ?

TOXCCT >>> GEII power

Re: Void

sps-itsec468-May-04 22:34

sps-itsec46

8-May-04 22:34

Sorry, I don't know if this autorun()-function is something special, but if you have a function which has void as return type you can just use the instruction return; to end the function (without any value) or just leave out the return instruction completely.

Hope it helps...

Regards, mYkel

Re: Void

soul.ripper9-May-04 7:09

soul.ripper

9-May-04 7:09

no i cant use return;
or leave out the return instruction
it gives errors with other functions

ExitProcess(0); works good

Greets jeroen

thanx for your time Big Grin | :-D

Re: Void

Anonymous9-May-04 9:30

Anonymous

9-May-04 9:30

ehm... yes you can!

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.