[GAP Forum] listing simple groups

[Hulpke,Alexander]

Dear Keith, Dear Forum,

>    it:=SimpleGroupsIterator(1);;
>   
> runs out of memory at a little over 20,000 with using gap -o 200g.
> 
> So I presume it's keeping all the smaller groups, or at least some information 
> about them.  How do I remove all the older stuff from memory as I go along?

GAP is not keeping the groups, but it is keeping data about the finite fields created, and PSL2’s will create a lot of them. (There is no way to avoid this — finite field data is never cleaned out once the finite field was created.)

However in many cases one can deal with PSL2 in other ways, and thus there is an option to iterate through simple groups *excluding* psl2:

it:=SimpleGroupsIterator(1:nopsl2);;

which (I hope) will resolve the memory issue.

Best,

 Alexander (Hulpke)

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