Re: RealTime Priority? - C / C++ / MFC Discussion Boards

Manikandan12-Oct-04 23:40

12-Oct-04 23:40

I wanna set real time priority to my application.

At first a loader program runs myapp. Then I want to get the process id using exe name. With exe name i must be able to set its priority to REALTIME.

My concept may sound correct but i dont know how to program it. Anybody can help me;P

Re: RealTime Priority?

Arsalan Malik13-Oct-04 2:07

Arsalan Malik

13-Oct-04 2:07

SetThreadPriority(...)[^] Smile | :)

ARSALAN MALIK

Re: RealTime Priority?

Antony M Kancidrowski13-Oct-04 2:33

Antony M Kancidrowski

13-Oct-04 2:33

If you have control over the loader program you can use CreateProcess() to launch your application and use REALTIME_PRIORITY_CLASS in the creation flag.

Otherwise use SetPriorityClass()within your application to REALTIME_PRIORITY_CLASS - this will ensure that your application runs at Realtime priority always.

I would be carefull when creating programs that run at realtime as they *will* hog the processor and you can easily prevent other applications from responding.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fruity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

Re: RealTime Priority?

Manikandan13-Oct-04 5:22

Manikandan

13-Oct-04 5:22

I tried...but it doesn't work. I am in VC6. Does this stuffs work under VC6? In the loader program i am using the below code,

STARTUPINFO suInfo;
PROCESS_INFORMATION procInfo;
CString m_Process;
m_Process.Format(_T("%s\\my.exe"),curDir);

memset (&suInfo, 0, sizeof(suInfo));
suInfo.cb = sizeof(suInfo);

::CreateProcess(m_Process,
NULL, // can also be NULL
NULL,
NULL,
FALSE,
REALTIME_PRIORITY_CLASS,
NULL,
NULL,
&suInfo,
&procInfo);

if (procInfo.dwThreadId == NULL)
{
AfxMessageBox("nope");
}
else
{
::SetThreadPriority(&procInfo.dwThreadId,THREAD_PRIORITY_HIGHEST);
}

When I check in process viewer the class priority is "Very High", the thread priority remain "normal". Also when a thread runs in "my.exe" it's not given the highest priorities, i am free to access other programs.

Re: RealTime Priority?

Antony M Kancidrowski13-Oct-04 5:33

Antony M Kancidrowski

13-Oct-04 5:33

Manikandan wrote:
i am free to access other programs

You will always be able to access other programs even with Realtime priority set.

NOTE: Running under windows you can not set the application to have exclusive use of the processor.

I am puzzled, why would you want to do this?

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fruity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

Re: RealTime Priority?

Manikandan13-Oct-04 6:20

Manikandan

13-Oct-04 6:20

Hi Ant, my application is time sensitive. even mouse move will affect its normal operation. This is why i have to suspend other programs when my exe run a thread.

Actually i found a standalone program in the net that list out all the running programs (I give you the link asap). When i set the priority to real time (24). I found my program running fine while i cant even access the mouse.

But i want to do this programmatically.

Re: RealTime Priority?

Antony M Kancidrowski13-Oct-04 11:41

Antony M Kancidrowski

13-Oct-04 11:41

Manikandan wrote:
But i want to do this programmatically

I would have thought that my suggested launching would have worked. If I think of anything else you could try I will let you know.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fruity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

Re: RealTime Priority?

geo_m13-Oct-04 21:42

geo_m

13-Oct-04 21:42

Well, just a notice - Windows are not realtime OS, if you really need the RT features (for RT controlling a device or something like that) you better to go by some specialized RT OS or get some RT plugin for NT that replaces the standard scheduler.
Even if you set the process realtime priority and thread realtime priority the time scheduler can interrupt your process and will do it usually in the worsest possible time.

Re: RealTime Priority?

Manikandan13-Oct-04 21:51

Manikandan

13-Oct-04 21:51

hi thanks for you idea,

i did a google search with the string "Real Time plug in for NT" but i couldn't come across any windows compatible plug in's.

would you please refer me one Roll eyes | :rolleyes:

Re: RealTime Priority?

geo_m14-Oct-04 0:28

geo_m

14-Oct-04 0:28

just googled for "RealTime NT"
and got some results

Vectors vs Arrays

mcsherry12-Oct-04 23:03

mcsherry

12-Oct-04 23:03

Hi all,

Apologies if this has already been covered but I could find it anywhere.

The problem that I have is that a piece of software that I am working on used a lot of arrays and matrices (i.e. float* and float**), the problem that we where having was that the program was leaking memory like there was no tomorrow (about a meg every 10secs) and the program was crashing at 'innocent' parts of the code.
After spending quite a while trying to solve these errors I decided to go at it with a sledge hammer and change all of the arrays and matrices to STL vectors (i.e. vector for the arrays and a vector <vector> for the matrices). I've now finished making the changes and the program no longer leaks memory or crashes, however it now runs at about 50% slower. I've changed where the vectors are created so that they are only created once. This has improved things quite a lot however it is still noticibly slower about 10%, does anyone have any other easy optimisation methods that I can implement.

I've left the way that the program accesses the data the same using the [] and [][] brackets.

Any thoughts or suggestions will be gratefully received!
Andy

Re: Vectors vs Arrays

V.12-Oct-04 23:37

12-Oct-04 23:37

Hi,

If the type is known (in your case float) you could write your own vector class.
Do the maintance (new/delete) in there and use the good old (double if necessary) arrays.

Vector classes are always quite slow. If speed is primary you should use arrays.

hope this helps...

"If I don't see you in this world, I'll see you in the next one... and don't be late." ~ Jimi Hendrix

Re: Vectors vs Arrays

mcsherry12-Oct-04 23:47

mcsherry

12-Oct-04 23:47

cheers for your reply, I think I have now located where the bottle neck in the code is! basically we copy a BYTE array (about 23000 elements each time!) into another vector (of type unsigned char) about 20-25 times a second which is slowing the whole process down so I'm now currently looking at optimising the copying process

Re: Vectors vs Arrays

Mike Beckerleg13-Oct-04 0:05

Mike Beckerleg

13-Oct-04 0:05

One thing to do when copying into vectors is use reserve() first if you know how many ites you need to copy in. Saves a lot of time spent allocating and copying progressively bigger blocks of memory.

Mike

Re: Vectors vs Arrays

Kevin McFarlane13-Oct-04 6:36

Kevin McFarlane

13-Oct-04 6:36

V. wrote:
If speed is primary you should use arrays.

According to Stroustrup, vectors are as efficient as arrays. (See his web site.) So it must be a question of poor usage.

Kevin

Re: Vectors vs Arrays

Maximilien13-Oct-04 0:56

Maximilien

13-Oct-04 0:56

well, I think that if speed is important, you should go back and figure out why your application is leaking memory ... if using VC++ compile in debug mode, and use the DEBUG_NEW define macro to help you find where exactly is the leak; and/or use BoundChecker or some other 3rd party software helper to find te leaks.

you found ( from you other post ) that you copy a lot of arrays, maybe that's where you are leaking memory ...

remember that for each new there should be a delete and for each new [] there should be a delete []

Maximilien Lincourt
Your Head A Splode - Strong Bad

Re: Vectors vs Arrays

mcsherry13-Oct-04 2:40

mcsherry

13-Oct-04 2:40

thanks everyone for your suggestions, what I've done is build the release version and it 'appears' to be fast enough for our needs. I'm currently in the process of verifying this through the code.

Andy,

Re: Vectors vs Arrays

Kevin McFarlane13-Oct-04 6:37

Kevin McFarlane

13-Oct-04 6:37

According to Stroustrup, vectors are as efficient as arrays. (See his web site.) So it must be a question of poor usage.

Kevin

CString += CString :: doesn't do the trick?

V.12-Oct-04 22:39

12-Oct-04 22:39

Hi,
I want to read a line of text from file.
Therefore I use following code:

			<br />
do{<br />
fscanf(readfile, "%s", line);<br />
text += " ";<br />
text += line;<br />
}<br />
while(line.Find("\n") < 0);<br />

if I debug I can see that line will contain text until the next whitespace. So far so good, but it seems that text += line; doesn't add this value to text.

Does anybody know why?

tnx!

"If I don't see you in this world, I'll see you in the next one... and don't be late." ~ Jimi Hendrix

Re: CString += CString :: doesn't do the trick?

RChin12-Oct-04 23:21

RChin

12-Oct-04 23:21

Ignore my response below; I didn't see the CString title! D'Oh! | :doh:

The first thing that comes to mind why it would not visually append would be that line is not null terminated.
Also I think the debug watch window only displays string values up to a certain length, then its truncated. I know that this was so for VS6, not sure for VS.7

[EDIT]

That is because
text += " "cannot be used on string variables.
I am assuming that text is a character buffer. If this is the case try:

..
_tcscat(text,_T(" "));// you could also use strcat() for non-unicode progs.
_tcscat(text,line);
..

[/EDIT]

I Dream of Absolute Zero

Re: CString += CString :: doesn't do the trick?

V.12-Oct-04 23:32

12-Oct-04 23:32

RChin wrote:
text += " " cannot be used on string variables.

OMG | :OMG:

I didn't know that, it worked fine for me, I use it all the time?

line and text are both CStrings, the " " is appended, but the line variable isn't. I suppose this has something to do with the fscanf function, but nonetheless it seems very strange to me.

tnx for the reply though.

PS: I've tried text = text + line; and text.Append(line); too, but nothing... Confused | :confused:

"If I don't see you in this world, I'll see you in the next one... and don't be late." ~ Jimi Hendrix

Re: CString += CString :: doesn't do the trick?

David Crow13-Oct-04 3:39

David Crow

13-Oct-04 3:39

V. wrote:
fscanf(readfile, "%s", line);
...
while(line.Find("\n") < 0);

If line is a CString object, it cannot be used as the third parameter to fscanf().

Assuming you are wanting to read lines from the file, there are at least two methods that make more sense. The first is to use "%[^\n]" instead of "%s". This will read everything up to the '\n' character. The second is to create a CStdioFile object and use its ReadString() method.

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Re: CString += CString :: doesn't do the trick?

V.13-Oct-04 4:39

13-Oct-04 4:39

tnx, this seems to work fine now Smile | :)

"If I don't see you in this world, I'll see you in the next one... and don't be late." ~ Jimi Hendrix

Re: CString += CString :: doesn't do the trick?

Phil J Pearson14-Oct-04 5:15

Phil J Pearson

14-Oct-04 5:15

The problem lies in

fscanf(readfile, "%s", line);

You cannot pass a CString variable as the parameter to fscanf. In this case it needs a char *

You will have to use a char array, or perhaps line.GetBufferSerLength(?) (see MSDN)

In either case you'll have to have some idea of the expected line length and cope with the possibility of buffer overflow. Think about a complete redesign.

The opinions expressed in this communication do not necessarily represent those of the author (especially if you find them impolite, discourteous or inflammatory).

thread safe lazy singleton intialization

peterchen12-Oct-04 22:09

peterchen

12-Oct-04 22:09

Hi,

I have a problem to find a good pattern for Initializing some data once on demand, in a thread-safe manner.

My first (not thread-safe) stab at it would be:

void GetSomething(int index)
{
  static CSomethingTable table;  // initialized the first time we come in here - sweet!
  return table[index];
}

I can ry to put a critsect around the table intialization, but I regulary end up with the same problem.

Any takers?

we are here to help each other get through this thing, whatever it is Vonnegut jr.

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