[GAP Forum] Extending Memory for GAP tasks on Macs OS X

[Alexander Hulpke]

Dear Sandeep Murthy,

> I am running a GAP program (on a Mac Intel-dual core
> running OS X Leopard) which has to search
> in the space of all triples of subsets of a
> given group of size n, this space being 2^(3n)
> large.  At present, it seems that if n > 6 then
> GAP fails due to lack of permitted memory.

I suppose you get the GAP error message about running out of memory  
and GAP ends in the brk>-loop.
This is triggered once GAP allocates more than 256MB of memory (the  
limit is a few years old, one probably could set it higher for modern  
machines), it is there to avoid a ``runaway'' GAP-process allocating  
memory to a point that severely distresses a system also used for  
other purposes at the same time. (If you call GAP with command line  
option `-g', it will display the amount of memory allocated at each  
garbage collection and give you an idea about its footprint.)

In principle, you could type
return;
and continue with more memory allocated but this is clumsy and  
infeasible for batch jobs.

A better solution however would be to call GAP with the -o command  
line option to set the warning level higher:
gap -o 1024m
would do 1GB for example. On a 2GB OSX machine I would probably keep  
this around 1GB if you want to do other things (email, web browsing)  
at the same time.

Hope this helps,

    Alexander Hulpke

-- Colorado State University, Department of Mathematics,
Weber Building, 1874 Campus Delivery, Fort Collins, CO 80523-1874, USA
email: hulpke at math.colostate.edu, Phone: ++1-970-4914288
http://www.math.colostate.edu/~hulpke