Segmentation fault in creating 2D array of large size in c++

Question

I have allocated a 2D array of size 5000 x 4859 using new() in C++ from a file.

class input
{
public :
int **mytable;
int rows;
int columns;

input()
{
   rows=5008;
   columns=4859;


     std::ifstream file("test.txt");
     mytable=new int *[rows];

      for(int i=0;i<rows;i++)
      {
             mytable[i]=new int [columns];
      }

// read the input and inserted them into the array.
}
int ** gettable()
{
   return mytable;
}

Then in another function where am using mytable through a pointer.

void someFunction()
{
int ** table;
input file;
table= file.gettable();

// doing neccessary operations.

}

When I decrease the size of the table to 500 x 500, it works fine but for large size it gives an std:: bad alloc error . Where did I go wrong? Please help.

bad_alloc == you can not allocate more memory

tkausl
– tkausl

2016-06-26 06:10:35 +00:00
Commented Jun 26, 2016 at 6:10 — tkausl
– tkausl, Commented Jun 26, 2016 at 6:10

Community · Accepted Answer · 2017-05-23 11:51:27Z

2

This should be of help,Creating large arrays in c++. Some relevant things you can think about when creating your arrays. {Though I can run and work with a 4000 by 4000 array of array (possibly because of the system configuration), it fails for 40000 by 40000.}

edited May 23, 2017 at 11:51

CommunityBot

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answered Jun 26, 2016 at 7:34

zobe kenobe

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Comments

orbitcowboy · Accepted Answer · 2016-06-26 06:47:18Z

0

You are trying to allocate too much memory. Please take a look at bad_alloc:

std::bad_alloc is the type of the object thrown as exceptions by the allocation functions to report failure to allocate storage.

Obviously you exceed the allowed memory limit of your operating system.

answered Jun 26, 2016 at 6:47

orbitcowboy

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1 Comment

Ankita Saha Over a year ago

Thanks for your reply. But how should I create a 2D matrix as large as this?

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