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Leonard Soicher writes in his e-mail message of 1994/07/28

The new StabChain function in Gap 3.4 is very useful for my work on

graphs and geometries, since I often know the size of a given group

acting on a graph. However, sometimes I only know an upper bound, and

was pleased to see that StabChain offers the option of specifying this

upper bound through the limit parameter. I was disappointed, however,

to find that with this option, StabChain appears to take as long as

when given no extra information, even when this upper bound is

achieved. Please tell me how to fix this!

The 'limit' option is currently only honoured by the random method.

The default however is the deterministic method.

The easiest solution is to force using the random method. You do this

with the 'random' option, using any value less than 1000.

gap> C := Combinations( [1..12], 4 );; gap> G := Operation( SymmetricGroup(12), C, OnSets );; gap> StabChain( Copy(G), rec( random := 1000, limit := Factorial(12) );; gap> time; 62353 gap> StabChain( Copy(G), rec( random := 999, limit := Factorial(12) );; gap> time; 4867 gap> StabChain( Copy(G), rec( random := 1000, limit := Factorial(13) );; gap> time; 62524 gap> StabChain( Copy(G), rec( random := 999, limit := Factorial(13) );; gap> time; 64566

Of course there is a small chance that the random method will fail.

But with 'random := 999', it is extremly small.

Martin.

-- .- .-. - .. -. .-.. --- ...- . ... .- -. -. .. -.- .- Martin Sch"onert, Martin.Schoenert@Math.RWTH-Aachen.DE, +49 241 804551 Lehrstuhl D f"ur Mathematik, Templergraben 64, RWTH, 52056 Aachen, Germany

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