Dear GAP Forum,

We occasionally get e-mail enquiries about suitable hardware for running GAP.
Recently Charles Leytem mailed gap-trouble with an enquiry about high-end
hardware, and I thought that other members of the forum might be able to help
him, or might be interested in the limited information that we could provide.
Here, with his permssion, is his enquiry and our response:

------- Forwarded Messages

From: Charles Leytem <charles.leytem@ci.educ.lu>

To: gap-trouble@dcs.st-and.ac.uk
Subject: memory, processor speed

I am thinking of getting a faster machine to run GAP on.

Under LINUX some verz strong affordable computers are available.

up to 2 GB RAM

up to 4 processors (500 Mhz)

I am wondering if you have anzy information about GAP's performance in
relation to high amounts of memory, processor speed and the number of
processors.
What is the maximal amount of memory used by GAP?
Thank you

Charles Leytem

------- End of Message 1

At GAP headquarters we do not have any experience with quite such powerful
machines, but the reply summarises what we do know about running GAP on big or
fast systems.

------- Message 2

To: Charles Leytem <charles.leytem@ci.educ.lu>

From: Steve Linton <sal@dcs.st-and.ac.uk>

Dear Charles,

To my knowledge no one has run GAP on quite such a powerful x86 system as you
describe.

Our general experience is that overall GAP performance from a system closely
follows the SPECInt95 benchmark, results of which can be found at
http://www.specbench.org, but that relative performance on individual tests
can vary quite a bit between styles of processor. For GAP 4.1, you get roughly
3000 GAP4stones per SPECINT95 baseline point, at least on the processors we
have tried (non-Xeon Pentium II and III, Compaq alpha 21264).

GAP does not (at present, or in the near future) make use of more than one
processor for a single GAP session, however the ParGAP/MPI package by Gene
Cooperman does allow multiple GAP sessions to communicate, and supplies some
higher level automation for task distribution.

In principle GAP on a 32 bit machines should be able to use close to 4GB of
memory, provided that the OS can offer it in one contiguous piece, although
our biggest Linux machine has only 1GB, so we have not been able to test
beyond this. On our Linux system (RedHat 6, with a 2.2.10 kernel) it is
necessary to link GAP statically to access more than about 500MB of workspace,
because otherwise the shared libraries break up the free memory. With static
linking, very large workspaces do not seem to present a problem.

Do let us know if you get such a machine, and how you get on.

Steve Linton

------- End of Forwarded Messages