OutOfMemoryException when allocation large memory blocks

Dear Softwaredevelopers,

In my application I have to allocate a huge amount of memory but the following C# console programm creates an OutOfMemoryException when I try to allocate memory >512 MB. and I wonder why.

My System:
Intel Core2 Quad CPU 3GB
Windows XP 32-Bit
Visual Studio 2008
available free memory 2.3GB

Can anybody help?

Greetings Christian


using System;
using System.Collections.Generic;
using System.Text;

namespace MemoryAllocation
{
class Program
{
static void Main(string[] args)
{
int size = 2;

while (size > 0)
{
Byte[] b = new Byte[size];

for (int i = 0; i<size; ++i)
b[i] = 13;
size *= 2;
}

}
}
}

What's your virtual memory set to? I think that can sometimes cause a cap on your available space for a byte array.

The while( size > 0 ) is causing an infinite loop. That's why you're running out of memory (because size is always greater than 0).

the execption occurs when I have 2.3 GB free space and want to allocate more than 512MB...
in the while loop I only wanted to find out what the limit is.
It also occurs withot the while loop.
the memory will be and is cleaned by the garbage collector.

As Arjay said, you have no terminating condition in your while loop; 'size' is always greater than 0 because you never decrease it (you actually add to it).

Quote:

---

Originally Posted by guentherc

the execption occurs when I have 2.3 GB free space and want to allocate more than 512MB...
in the while loop I only wanted to find out what the limit is.
It also occurs withot the while loop.
the memory will be and is cleaned by the garbage collector.

---

You might think so, but in this type of tight loop, you'll run out of memory before the cg has a chance to run. Or, even if the cg has a chance to run, it won't be able to keep up.

Or it's possible that your operating system does not have 512MB of contiguous free RAM and therefore cannot fulfill your request. Every programming language will hit the exact same issue, though the exact point at which they hit it will vary depending on what your operating system is doing.

It's very unusal for an application to actually require such large memory buffers. Generally you can use a chunked approach and process 4MB at a time (or less) which can result in a more performant application. Have you considered that approach?