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

Hi John,

use char* a=new char[MAX]. It's a stack size problem. Your favorite search engine can tell you all about it ;-)

Cheers, Axel.

John Zoidberg wrote:
> 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?
>
>
Received on Mon Jul 09 2007 - 18:23:23 CEST