Re: What is the maximum acceptable size of an array?

From: sean hayes <seanowenhayes_at_yahoo.es>
Date: Tue, 10 Jul 2007 17:12:23 +0200 (CEST)

Hi all,

can any one tell me how to get off of this mailing list?

regards

Sean

John Zoidberg <zohn.joidberg_at_gmail.com> escribió: And why does it not happen in programs compiled with gcc/g++?  What's the exact stack size of ROOT?  

 I used static allocation on purpose since it usually causes less problems than dynamic allocation.  I guess I was wrong. ^^'  

On 7/9/07, Victor Perevoztchikov <perev_at_bnl.gov> wrote: Hi John,  sure it is related to stack size. When it is not compiled, then this array created by new.  If you will do instead of
   char a[MAX];
char *a = new char[MAX];
 and at the end delete [] a
 it will work allways correctly
 Victor      

  Victor M. Perevoztchikov perev_at_bnl.gov Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000 tel office : 631-344-7894; fax 631-344-4206;

• Original Message ----- From: John Zoidberg To: roottalk_at_root.cern.ch Sent: Monday, July 09, 2007 12:02 PM Subject: [ROOT] What is the maximum acceptable size of an array?

I've encountered a strange problem in one of my macros. I managed to reduce it to an array size problem.

This macro runs without errors when compiled (.L toto.C+) with "#define MAX 1972432" and exits root without any message if compiled with "#define MAX 1972433":
//includes

#include <iostream>
using namespace std;

//OK

#define MAX 1972432
//not OK

 //#define MAX 1972433

//main function

int toto()
{

   char a[MAX];   

     cout<<"MAX="<<MAX<<endl;
     cout<<"total size="<<MAX*sizeof(char)<<"    bytes"<<endl;
  cout<<"total    size="<<(float)MAX*(float)sizeof(char)/1024.<<"    Kilobytes"<<endl;

  cout<<"total size="<<(float)MAX*(float)sizeof(char)/(1024.*1024.)<<" Megabytes"<<endl;   cout<<"total size="<<MAX*sizeof(char)*8<<" bits"<<endl;   

      return(0);
}

You might have to change the limit values of MAX to see this problem on your PC. I noticed that it's quite random sometimes. Sometimes it worked with 1972432 and sometimes not. I also recommend quitting and restarting ROOT after each test because it seems to always work if you stay in the ROOT shell even after recompiling.

Other tests I made:

This macro runs without error when not compiled (.x toto2.C):
//includes

#include <iostream>
using namespace std;

//OK

#define MAX 10000000
//not OK

 //#define MAX 1972433

//main function

int toto2()
{

   char a[MAX];   

     cout<<"MAX="<<MAX<<endl;
     cout<<"total size="<<MAX*sizeof(char)<<"    bytes"<<endl;
  cout<<"total    size="<<(float)MAX*(float)sizeof(char)/1024.<<"    Kilobytes"<<endl;

  cout<<"total size="<<(float)MAX*(float)sizeof(char)/(1024.*1024.)<<" Megabytes"<<endl;   cout<<"total size="<<MAX*sizeof(char)*8<<" bits"<<endl;   

      return(0);
}

This C++ program compiles and runs without error:
//includes

#include <iostream>
using namespace std;

//OK

#define MAX 10000000
//not OK

 //#define MAX 1972433

//main function

int main()
{

   char a[MAX];   

     cout<<"MAX="<<MAX<<endl;
     cout<<"total size="<<MAX*sizeof(char)<<"    bytes"<<endl;
  cout<<"total    size="<<(float)MAX*(float)sizeof(char)/1024.<<"    Kilobytes"<<endl;

  cout<<"total size="<<(float)MAX*(float)sizeof(char)/(1024.*1024.)<<" Megabytes"<<endl;   cout<<"total size="<<MAX*sizeof(char)*8<<" bits"<<endl;   

      return(0);
}

So, is there any rational explanation to this? Should I use TCloneArrays or TNtuples instead?                      

---

LLama Gratis a cualquier PC del Mundo.
Llamadas a fijos y móviles desde 1 céntimo por minuto. http://es.voice.yahoo.com Received on Tue Jul 10 2007 - 17:12:32 CEST