From: Andreas Dorn <adorn AT ix DOT urz DOT uni-heidelberg DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: Large Arrays
Date: Thu, 05 Jul 2001 15:54:27 +0200
Organization: University of Heidelberg, Germany
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

My problem:
I need a really large array for a matrix (~100 MB).
With linux/unix and gcc that worked fine, but with dos/windows this
never worked. Even with 256MB RAM and "small" arrays (<5MB) it didn't
work.

The initialisation of the array looks like this:

int main(void)
{
  const int Dimension=5000;

  float TheMatrix[Dimension][Dimension];
  int i,j;

  for(i=0; i<Dimension; i++){
    for(j=0; j<Dimension; j++){
      TheMatrix[i][j]=0.0;
    };
  };

  return(0);
}

For example Dimension=300 works fine on my computer(32MB-RAM,win95).
Dimension=600 compiles with djgpp and crashes when executed.

My questions:
- I don't have much experience with dos/windows compilers. What is the
reason for the memory-problems? And how much memory do I get for an
array under win3.11, win95, ..?

- Is there an easy solution (a compiler option or something) to get a
working array?  (option: -WA <working array> :-))

- Will it work, if I try to allocate the memory for the array myself
(...writing my own array class), or is there a fundamental problem?

Help welcome.

Andreas Dorn