Date: Fri, 9 Jul 1993 21:50:19 -0600
From: jweiss AT silver DOT sdsmt DOT edu (John M. Weiss)
To: djgpp AT sun DOT soe DOT clarkson DOT edu


Earlier today I wrote:

> Does anyone know how to query the amount of available physical RAM
> using gcc? Turbo C provides the coreleft() routine, but this is not
> part of the standard C libraries. I seem to remember seeing some code
> that made use of brk/sbrk to do this once upon a time...

In response to a couple of replies to this message, let me be slightly
more explicit. I am interested in finding out how much *electronic* heap
space is available to my program at any given time. One solution might be
to put malloc() or sbrk() in a loop, until all heap space is exhausted
and a NULL pointer is returned. In addition to the obvious inefficiency,
the virtual memory facility of DJGPP causes problems with this approach.

Motivation for the above:
I am writing an image processing program that makes use of 2-D fast
Fourier transforms. 2-D FFT's are very memory-intensive, involving
complex Fourier coefficients (i.e., 8 bytes per pixel). This memory
gets allocated/deallocated dynamically with malloc()/free(). Although
in-memory FFT's are not too bad, even the so-called "fast" transform is
*extremely* slow if disk-swapping is required. Therefore it is important
for me to know in advance whether or not I have enough physical memory
(not virtual memory) available to do everything in RAM.

Any suggestions? Thanks again - JW

Dr. John M. Weiss, Associate Professor
Department of Mathematics and Computer Science
South Dakota School of Mines and Technology
501 East St. Joseph Street
Rapid City, SD 57701-3995
605-394-6145    jweiss AT silver DOT sdsmt DOT edu