gap&gt; ps := ParabolicQuadric(4,4);
Q(4, 4)
gap&gt; g := CollineationGroup(ps);
PGammaO(5,4)
gap&gt; l1 := Random(Lines(ps));
&lt;a line in Q(4, 4)&gt;
gap&gt; l2 := Random(Lines(ps));
&lt;a line in Q(4, 4)&gt;
gap&gt; g1 := Stabilizer(g,Set([l1,l2]),OnSets);
&lt;projective collineation group of size 2304 with 6 generators&gt;
gap&gt; time;
2633
gap&gt; g2 := FiningSetwiseStabiliser(g,Set([l1,l2]));
#I  Computing adjusted stabilizer chain...
&lt;projective collineation group with 5 generators&gt;
gap&gt; time;
70
gap&gt; g1=g2;
true
