Dear Forum,

On Sat, 22 Jan 2000, John Murray wrote:

>Dear Forum, I'm running GAP3 under Windows 95.
>Frequently GAP terminates in the middle of a
>memory hungry operation with a message such as:
>
>DPMI: not enough memory (0x01f60000 bytes).
>
It's running as an MSDOS application (thus, with various
awful limitations on the way the memory is allocated, due to the usage
of 16-bit addresses)
that uses DMPI (a library to make addresses look 32-bit instead).

IMHO, this configuration isn't the best way to manage memory allocation,
by any means.

GAP4 uses a better scheme while running under
Windows. In particular, it uses native 32-bit addressing.
Things should work better there. Still, there is Cygwin, a 3rd party
software layer between GAP and Windows, that translates back and force
Posix-style system calls that GAP uses to communicate with the operating
system.
Moreover, Cygwin is not very stable on Win 95, being primarily
Win NT4.0 tool.
Also, so-called "Windows Software Packs", i.e. ugrades to Windows, are
known to break functionality of Cygwin here and there.

In view of all this, I would be surpised if the stability (as far as
the interface with OS is concerned) of GAP on Unix
platforms can be also be achieved on Windows without resorting to
porting GAP OS calls directly to Windows.

The latter is not an impossible task,
but it requires certain amount of time and expertise.
I don't know if anyone tried this.

>My PC has 32 MB of RAM, and 1f60000 is
>31,850,496 in decimal. Is this indeed a problem
>with my RAM? I thought that if a programme
>exceeds the RAM limit, the CPU is supposed
>to "swap" memory in and out of RAM (I have
>over 200 MB of free space on my C drive).
>
>By the way, using the -a option with GAP does
>not seem to improve matters.
>
>Any help or comments (especially an overview
>of how memory is allocated to GAP) would be
>appreciated.
>
Perhaps the easiest way to get GAP3 to run well on your machine
would be to install Linux there and run it under Linux.

Less radical in some sense would be to use GAP4 instead of GAP3.

Hope this helps to understand the Windows-specific
issues that you're facing.

I'd leave to others to comment on GAP memory management.
(It seems that this question was already rasied on this forum.
Did you try searching the GAP Forum archives on
http://www-history.mcs.st-and.ac.uk/~gap/ ?)

Dima

---
Dmitrii Pasechnik
e-mail: dima@cs.uu.nl
http://www.cs.uu.nl/staff/dima.html