🚀 go-pugleaf

"Deniel" <DenielMail@Internet.com> writes:

> int MySize, *MyBuffer;
>
> MySize = 0.85 * pow( 2, 31 ); // 2^31 = 2GB 
> MyBuffer = new int[MySize ]; 
>
>
>>There is no portable way to achieve what you are looking for, and I
>>also wouldn't expect there to be a way at all on most common
>>platforms.
>
> I don't understand, where exactly is the problem? 

In your requirements :-)

Most common platforms are multitasking systems. Now consider what
happens if you start your program twice.

Cf. http://blogs.msdn.com/oldnewthing/archive/2005/06/07/426294.aspx


> If i whould wrtie this - 
>
> MyBuffer = new int[200]; 
>
> there whould be no problem right? 

Probably. Because the overhead per process is likely to hit a
different system boundary before all the physical memory is used up if
you try start your program the sufficient number of times to achieve
the effect described above.


> but if i write this - 
>
> MyBuffer = new int[0.85 * 0x80000000]; // 85% of 2GB 
>
> Then THERE WILL be a problem.... right?

Yes.


> So where does the problem starts? what is the limit size that
> start making problems?

It doesn't start at a specific number of ints per array, but at your
requirement.


There may be platforms that you can ask for memory that won't be
swapped. The C++ language doesn't offer a portable way to access these
APIs, though.