Dear GAP-Forum.

I have some problems with (I guess) implementation of GAP.

I do work with finite Projective Special Linear Groups. At the
moment they are being represented as some permutation groups

(namely, the action of SLs on lines). (I very much appreciate
the help of Alexander Hulpke, who provided me with the text of
GAP procedure for this). This works OK (much faster than
calculations with matrices for SL) until the order of the group
goes to several billions. (like PSL(3,17) or PSL(3,19) or
PSL(4,5)).

For these cases GAP can construct the group,
calculate the size,
construct conjugacy classes,

but it can't calculate centralizer of the element.

I did the job in background with redirecting of input-output and
GAP would just stop working without any error message.

So is it a bug in GAP (I can provide exact text of the program to nail it) or
is it just natural restriction of the size?

Also I would appreciate very much the help on how to collect all
involutions in the group. Now I'm doing by computation of all
conjgacy classes (which I don't need) and then picking ones with
elements of order 2.

Thank you very much,

Michael.