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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.

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